Collection and Gravimetric Analysis December 2019

Duluth Laboratories & Administration 5013 Miller Trunk Highway Duluth, Minnesota 55811

Coleraine Laboratories One Gayley Avenue P.O. Box 188 Coleraine, Minnesota 55722

Submitted by: Stephen D. Monson Geerts1, George Hudak1, Virgil Marple2,

Dale Lundgren3, Lawrence Zanko1, and Bernard Olson2 1Natural Resources Research Institute, University of Minnesota Duluth

2Department of Mechanical Engineering, University of Minnesota Twin Cities 3University of Florida - Gainesville

Date: December 2019 Report Number: NRRI/RI-2019/29

Project No. 1806-10416-20080

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Minnesota Taconite Workers Health Study:

Environmental Study of Airborne Particulate Matter in Mesabi Iron Range Communities

and Taconite Processing Plants — Taconite Processing Facilities Particulate Matter

Collection and Gravimetric Analysis

http://www.nrri.umn.edu

Cover Photo Caption: Particulate matter sample and data collection inside one of six taconite processing facilities located on the Mesabi Iron Range in northeastern Minnesota. Recommended Citation: Monson Geerts, S.D., Hudak, G., Marple, V., Zanko, L., Lundgren, D., and Olson, B. 2019. Minnesota Taconite Workers Health Study: Environmental Study of Airborne Particulate Matter in Mesabi Iron Range Communities and Taconite Processing Plants – Taconite Processing Facilities Particulate Matter Collection and Gravimetric Analysis. Natural Resources Research Institute, University of Minnesota Duluth, Report of Investigation NRRI/RI-2019/29. 102 p. + appendices. Key words: taconite, Mesabi, particulate matter, airborne, processing, plant, gravimetric Natural Resources Research Institute University of Minnesota, Duluth 5013 Miller Trunk Highway Duluth, MN 55811-1442 Telephone: 218.788.2694 e-mail: [email protected] Web site: https://www.nrri.umn.edu/research-groups/minerals-and-metallurgy ©2019 by the Regents of the University of Minnesota All rights reserved. The University of Minnesota is committed to the policy that all persons shall have equal access to its programs, facilities, and employment without regard to race, color, creed, religion, national origin, sex, age, marital status, disability, public assistance status, veteran status, or sexual orientation.

Visit our website for access to this and other Natural Resources Research Institute publications: http://www.nrri.umn.edu/publications.

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NRRI/RI-2019/29 – Taconite Facilities Gravimetric Analysis i

UNIVERSITY OF MINNESOTA DULUTH – NATURAL RESOURCES RESEARCH INSTITUTE (NRRI) ENVIRONMENTAL PARTICULATE MATTER CHARACTERIZATION

Taconite workers on the Mesabi Iron Range (MIR) in northeastern Minnesota have displayed a

higher than normal incidence of the rare disease Mesothelioma (MDH, 2003; 2007). To better-understand this higher level of occurrence, the Minnesota Legislature funded the $4.9-million-dollar Minnesota Taconite Workers Health Study (MTWHS). Initiated in 2008, this five-component study was a collaborative effort between the University of Minnesota’s School of Public Health (SPH), the University of Minnesota Medical School (UMMS), and the University of Minnesota Duluth’s Natural Resources Research Institute (NRRI). The University’s School of Public Health and Medical School performed the study’s four health-related components (Finnegan and Mandel, 2014). The study’s fifth component, “Environmental Study of Airborne Particulate Matter,” was conducted by the NRRI and is summarized in this Executive Summary Report. The study comprised physical, mineralogical, and chemical characterization of airborne particulate matter (PM) in MIR taconite processing facilities and selected MIR communities. Respirable mineral PM of a specific size, shape, and mineralogy—referred to as elongate mineral particles (EMPs)—were of special interest. Ambient aerosol PM samples were collected from five MIR communities, three Minnesota background locations, and the six operating taconite processing plants located on the MIR. Components of this PM characterization included: gravimetric analysis, mineralogical identification, mineralogical concentration evaluations, PM morphological characterizations, and PM chemical characterizations.

The fundamental question addressed by this study is, “What is in the air?” Additionally, a characterization of EMPs from age-dated lake sediments in two MIR lakes was performed in an effort to obtain historical data regarding the characteristics of past PM conditions; in a general sense, to investigate what had been in the air. Consequently, the research effort focused on providing answers to the following underlying questions: How much PM is in the air? What is the size distribution of the PM in the air? What are the physical characteristics of the PM in the air? What are the mineralogical characteristics of the PM in the air? What are the chemical characteristics of the PM in the air? and What historical trends in PM mineralogy, physical characteristics, and chemical composition

can be identified from studies of dated sedimentary deposits in lakes located in close proximity to taconite operations on the MIR?

Disclosure and Disclaimer Statement The NRRI’s aerosol PM sampling protocols—including the equipment utilized and the data collected in this study—are not meant to represent, or to be considered a substitute for, ambient air monitoring as conducted and reported by regulatory agencies such as the Minnesota Pollution Control Agency (MPCA), Minnesota Department of Health (MDH), and the United States Environmental Protection Agency (USEPA). Any reference to State, USEPA, National Ambient Air Quality Standards (NAAQS), Occupational Health and Safety Administration (OSHA), and/or Mine Safety Health Administration (MSHA) standards is for illustrative and comparative purposes and is meant only to provide context to the findings in this NRRI study.

NRRI/RI-2019/29 – Taconite Facilities Gravimetric Analysis ii

EXECUTIVE SUMMARY: TACONITE PLANT GRAVIMETRIC ANALYSIS This report discusses the results of a gravimetric characterization from aerosol particulate matter (PM) within the Mesabi Iron Range (MIR) taconite processing plants. A total of 14 separate aerosol PM sampling events were conducted at the six taconite processing facilities operating at the time of this study on the MIR in northeastern Minnesota. All six facilities—coded as Plants A, B, C, D, E, and F using the same nomenclature as Finnegan and Mandel (2014)—were sampled at least once during active operation (11 total). Three facilities were sampled during total plant shutdown (inactive) in 2009. Two of the plants, A and F, were sampled three times each during active operation. These two plant locations were chosen for the spatial relationship of their respective ore sources (mines) to the Duluth Complex. This ~1.1-billion-year-old intrusion provided heat that resulted in thermal metamorphism of the Biwabik Iron Formation (BIF) that resulted in changes to the mineral, chemical, and physical characteristics of the iron formation at its eastern end (French, 1968; McSwiggen and Morey, 2008; Severson et al., 2009). Sampling of the taconite facilities occurred randomly during both summer season (defined for this study as May through October) and winter season (defined for this study as November through April). Each of the sampling events comprised two-hour-long sample collections (at approximately 30 L/minute) at four specific locations in each facility, including: 1) fine crusher; 2) concentrator – magnetic separator; 3) agglomerator – balling drums/discs; and 4) kiln – pellet discharge. These locations were chosen within the plants because they represent process locations where important physical and/or chemical changes to the raw material, as related to particle size and/or a change in mineralogical characteristics, take place. Equipment utilized in sample collection included: A) a Micro-Orifice Uniform Deposit Impactor (MOUDI: Marple et al., 1991; 2014), a device that collects a size-fractionated sample of PM, with PM aerodynamic diameters ranging from 30.0 to 0.056 micrometers (µm or microns); and B) a Total Filter Sampler (TFS) that collects all PM on a single substrate. This report specifically discusses the results of PM gravimetric analysis within the taconite processing facilities. The findings from this report are:

1. Based on the relative consistency of the geology of the BIF and the similarities of mining and processing the ore, statistical power of analysis was achieved through the 10 cumulative sample series collected in the five most-western plants. Four additional sample series were collected from the sixth plant on the east end of the BIF, where the geology/mineralogy of the iron formation has been modified by thermal metamorphism.

2. Substantial and significant differences in the amount of PM existed between the inactive and active plant processing operations. PM in the areas of active crusher and concentrator were found to be up to three times greater than in inactive plants. The process areas of active agglomerator and kiln were the dustiest areas of the plants and were found to contain 30–40 times the amount of PM compared with inactive plants.

3. The equipment and collection protocol used by the NRRI to sample the six plants was consistent throughout the sample collection period.

4. Our findings indicate that relative PM concentrations in each of the four process locations exhibited the same relationship from plant to plant. Ranked from ‘most’ (1) to ‘least’ (4), average PM concentration (measured in (µg/m3), including MOUDI total and PM2.5 fraction (respirable fraction), were: 1) the kiln areas; 2) the agglomerator areas; 3) fine crusher areas; and 4) the concentrator/magnetic separator areas. Variations were observed from plant to plant (due to varying ventilation systems, housekeeping, etc.).

5. Total PM and PM2.5 concentrations were higher in active plants versus inactive plants. However, the finer PM2.5 fraction comprised a higher percentage of the total percent PM in inactive versus active plants, likely reflecting that most PM in active plants is coarse-fraction and settles out of the atmosphere more rapidly.

NRRI/RI-2019/29 – Taconite Facilities Gravimetric Analysis iii

6. Comparisons of the PM (active) results from Plant A and Plant F (plants receiving three sampling events each) were statistically insignificant and were found to be similar to the average levels found in all active plants across the MIR.

7. Average, high, and low total PM concentrations (measured in µg/m3) from samples collected using the MOUDI (referred to as MOUDI Total Concentrations, or MOUDI Total) in the four process areas of the active plants were as follows:

Active Plant MOUDI Total Concentrations (µg/m3)

Average (µg/m3) High (µg/m3) Low (µg/m3)

Crusher 735.88 (488.23)*

1,570.79 F

278.39 D

Concentrator 578.28 (208.94)

885.82 A

141.01 C

Agglomerator 5,272.63 (4,831.32)

16,684.25 A

1,287.18 C

Kiln 7,357.82 (6,640.14)

20,980.17 E

445.53 C

(*standard deviation) 8. Average PM concentrations in the respirable PM2.5 fraction (measured in µg/m3), including

their respective percentage of the MOUDI Total, from samples collected using the MOUDI in the four process areas of the active plants were as follows:

Active Plant PM2.5 Concentrations - Fraction of MOUDI Total (µg/m3)

Average (µg/m3) High Low

Crusher 277.80 (154.04)*

577.31(µg/m3) – 41.6% PM2.5

A

118.09 (µg/m3) – 34.0% PM2.5

C

Concentrator 201.49 (72.26)

311.41(µg/m3) – 44.9% PM2.5

F

72.09 (µg/m3) – 51.1% PM2.5

C

Agglomerator 420.89 (213.07)

944.29 (µg/m3) – 5.7% PM2.5

A

239.28 (µg/m3) – 5.2% PM2.5

A

Kiln 495.66 (250.75)

948.76 (µg/m3) – 7.7% PM2.5

D

188.76 (µg/m3) – 40.4% PM2.5

C (*standard deviation)

NRRI/RI-2019/29 – Taconite Facilities Gravimetric Analysis iv

TABLE OF CONTENTS

EXECUTIVE SUMMARY: TACONITE PLANT GRAVIMETRIC ANALYSIS ................................................................... ii LIST OF TABLES ................................................................................................................................................... vi LIST OF FIGURES ............................................................................................................................................... viii LIST OF PHOTOS .................................................................................................................................................. ix LIST OF APPENDICES ........................................................................................................................................... ix INTRODUCTION ................................................................................................................................................... 1 BACKGROUND ..................................................................................................................................................... 1

What is Mesothelioma? .................................................................................................................................. 2 REGULATION CONCERNING PARTICULATE MATTER (PM) .................................................................................. 3 OBJECTIVES .......................................................................................................................................................... 8

Questions to be addressed ............................................................................................................................. 8 SAMPLING METHODOLOGY ................................................................................................................................ 9

Preliminary Statistical Analysis ..................................................................................................................... 12 STUDY AREA ....................................................................................................................................................... 12

Regional Geology .......................................................................................................................................... 12 Taconite Mines and Processing Plants .......................................................................................................... 13 Geology, Taconite Process Technology, and Sampling Numbers ................................................................. 16

PARTICULATE MATTER SAMPLING .................................................................................................................... 16 120 MOUDI II Cascade Impactor ................................................................................................................... 17 Respirable Weight Fraction PM2.5 ................................................................................................................. 20 Total Filter Sampler (TFS) .............................................................................................................................. 20 Substrates and associated analyses .............................................................................................................. 22 Sampling Protocol ......................................................................................................................................... 23 Gravimetric Analysis ...................................................................................................................................... 26 Safety ............................................................................................................................................................ 27

DATA REPORTING PROTOCOLS ......................................................................................................................... 27 RESULTS ............................................................................................................................................................. 51

Statistical Analysis ......................................................................................................................................... 58 Inactive Versus Active Plants .................................................................................................................... 58 Differences in PM between Western and Eastern MIR due to Metamorphism ....................................... 58 Zone 1 vs Zone 4 ....................................................................................................................................... 61 Plant Process Areas Ranked by PM ........................................................................................................... 61

FINE (SECONDARY) CRUSHER ............................................................................................................................ 61 Crusher Gravimetric Results ..................................................................................................................... 64 Crusher – Inactive PM2.5 ............................................................................................................................ 64 Crusher – Active PM2.5 .............................................................................................................................. 64

Concentrator/Magnetic Separator ............................................................................................................... 66 Concentrator Gravimetric Totals .............................................................................................................. 66 Concentrator – Inactive PM2.5 ................................................................................................................... 66 Concentrator – Active PM2.5 ..................................................................................................................... 66

Agglomerator/Balling Area ........................................................................................................................... 67 Agglomerator Gravimetric Totals .................................................................................................................. 67

Agglomerator – Inactive PM2.5 .................................................................................................................. 67 Agglomerator – Active PM2.5 ..................................................................................................................... 67

KILN/PELLET DISCHARGE ............................................................................................................................... 68 Kiln Gravimetric Totals .............................................................................................................................. 68 Kiln – Inactive PM2.5 .................................................................................................................................. 68

NRRI/RI-2019/29 – Taconite Facilities Gravimetric Analysis v

Kiln – Active PM2.5 ..................................................................................................................................... 68 Plant Multiple Sample Events ....................................................................................................................... 69

Plant A Summary ....................................................................................................................................... 69 Plant F Summary ....................................................................................................................................... 70

Particulate Matter Mass Percentages by Aerodynamic Diameter: Mode Comparison ............................... 70 RESULTS ............................................................................................................................................................. 71

Plant A Results .............................................................................................................................................. 72 Plant B Results ............................................................................................................................................... 73 Plant C Results ............................................................................................................................................... 74 Plant D Results .............................................................................................................................................. 75 Plant E Results ............................................................................................................................................... 76 Plant F Results ............................................................................................................................................... 77

DISCUSSION – PARTICULATE MATTER MASS PERCENTAGES AND AERODYNAMIC DIAMETER ........................ 78 Particle Size Analysis ..................................................................................................................................... 87

CONCLUSIONS ................................................................................................................................................... 92 Findings ......................................................................................................................................................... 92

HIGHLIGHTED FINDINGS .................................................................................................................................... 93 MOUDI Total PM Concentrations ................................................................................................................. 93

Fine Crusher .............................................................................................................................................. 93 Concentrator ............................................................................................................................................. 93 Agglomerator ............................................................................................................................................ 93 Kiln ............................................................................................................................................................ 93 Fine Crusher .............................................................................................................................................. 93 Concentrator ............................................................................................................................................. 94 Agglomerator ............................................................................................................................................ 94 Kiln ............................................................................................................................................................ 94

Summary of Plant Gravimetric Data ............................................................................................................. 94 Further work ............................................................................................................................................. 97

ACKNOWLEDGEMENTS ..................................................................................................................................... 97 REFERENCES ...................................................................................................................................................... 98 APPENDICES ..................................................................................................................................................... 102

NRRI/RI-2019/29 – Taconite Facilities Gravimetric Analysis vi

LIST OF TABLES Table 1. NAAQS for PM2.5 and PM10 (Source: https://www.epa.gov/criteria-air-pollutants/naaqs-

table). ..................................................................................................................................................... 4

Table 2. The taconite mining companies and their corresponding processing facilities that participated in this study. Generalized geographic locations are determined based on the location of the mine pit for the plant relative to the metamorphic Zone 2–Zone 3 mineralogical boundary as indicated by French (1968) and McSwiggen and Morey (2008). ................ 9

Table 3. P-values from multivariate comparisons among the five plants in the western MIR (Zone 1)................................................................................................................................................. 12

Table 4. MOUDI cascade impactor stages, ranges, and PM designations. ................................................. 18

Table 5. Fifteen-minute partial MOUDI stages and particulate matter ranges. ......................................... 19

Table 6. Regression analysis comparing MOUDI totals with TFS weights in two-hour sample. ................. 22

Table 7. Substrate and filter utilization in analytical procedures. .............................................................. 23

Table 8. Plant D: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%). ............................................................................................................ 29

Table 9. Plant B: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%). ............................................................................................................ 31

Table 10. Plant E: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%). ............................................................................................................ 33

Table 11. Plant C: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%). ............................................................................................................ 35

Table 12. Plant F: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%). ............................................................................................................ 37

Table 13. Plant A: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%). ............................................................................................................ 41

Table 14. Summary table of inactive sample concentrations by plant process, including both MOUDI totals and PM2.5 fraction – Weight/Volume Air (µg/m3), and PM2.5 representative percent (%) of MOUDI total. ................................................................................................................ 46

Table 15. Summary table of active sample concentrations by plant process, including both MOUDI totals and PM2.5 fraction – Weight/Volume Air (µg/m3), and PM2.5 representative percent (%) of MOUDI total. ................................................................................................................ 47

Table 16. Summary table of active sample concentrations from Plant F by process, including both MOUDI totals and PM2.5 fraction – Weight/Volume Air (µg/m3), and PM2.5

representative percent (%) of MOUDI total. ........................................................................................ 49

Table 17. Summary table of active sample concentrations from Plant A by process, including both MOUDI totals and PM2.5 fraction – Weight/Volume Air (µg/m3), and PM2.5

representative percent (%) of MOUDI total. ........................................................................................ 50

Table 18. Summary of mean and standard deviation of PM percentages and log10 transformed PM concentrations for different processes at Plants A, B, and D. ....................................................... 59

NRRI/RI-2019/29 – Taconite Facilities Gravimetric Analysis vii

Table 19. Summary of mean and standard deviation of PM percentages and log10 transformed PM concentrations for the western five plants compared with the eastern plant when plants are active. ............................................................................................................................................. 60

Table 20. Summary of mean and standard deviation of PM percentages and log10 transformed PM concentrations comparing Plants A and F when plants are active. ............................................... 62

Table 21. Summary of the mean and standard deviation of PM percentages and log10 transformed PM concentrations for the four process areas when plants are inactive and active. Means of each process were compared by Tukey’s ranking test. The PM from different processes were ranked from (A) largest to (C) smallest by letters besides mean concentrations. Cells with the same letter under the same column indicate no significant difference. ............................................................................................................................................ 63

Table 22. Plant A – PM1, PM2.5, PM10, and TOTAL PM summaries. ............................................................. 72

Table 23. Plant B – PM1, PM2.5, PM10, and TOTAL PM summaries. ............................................................. 73

Table 24. Plant C – PM1, PM2.5, PM10, and TOTAL PM summaries. ............................................................. 74

Table 25. Plant D – PM1, PM2.5, PM10, and TOTAL PM summaries. ............................................................. 75

Table 26. Plant E – PM1, PM2.5, PM10, and TOTAL PM summaries. ............................................................. 76

Table 27. Plant F – PM1, PM2.5, PM10, and TOTAL PM summaries. ............................................................. 77

NRRI/RI-2019/29 – Taconite Facilities Gravimetric Analysis viii

LIST OF FIGURES Figure 1. Generalized taconite processing flow diagram (USEPA, 2001). ..................................................... 6 Figure 2. Study area sampling locations. MIR community sampling occurred in Keewatin, Hibbing,

Virginia, Babbitt, and Silver Bay. Background community sampling took place in Ely, Duluth, and Minneapolis (see left side of figure). Taconite processing plants that were also sampled during the NRRI’s PM characterization studies included Keetac, Hibtac, Minntac, Utac, Minorca, and Northshore (right side of figure). ................................................................................... 10

Figure 3. Locations of taconite plants and communities on the MIR with respect to the BIF (brown-red color), the geological unit mined for iron on the Mesabi Range. Metamorphic zones 1, 2, 3, and 4 refer to different mineralogical zones associated with the BIF that were identified by French (1968) and further refined by McSwiggen and Morey (2008). These zones indicate the mineralogical changes occurring in the BIF progressing along strike from west to east. Mineralogical changes in zones 3 and 4 were the result of thermal metamorphism of the BIF during intrusion of Duluth Complex-related magmas ~1.1 billion years ago. The mineralogical characteristics of these zones are summarized below the map. ......................................................... 11

Figure 4. X/Y plot of plant concentrations – MOUDI totals with Total Filter counterparts in Weight/ Volume Air (µg/m3). ............................................................................................................................. 21

Figure 5. Comparison of all plant samples by plant activity: MOUDI totals as concentrations (Weight/Volume Air – µg/m3). ............................................................................................................. 52

Figure 6. Comparison of all plant samples by plant activity: PM2.5 fractions of MOUDI totals as concentrations (Weight/Volume Air – µg/m3). ................................................................................... 53

Figure 7. Comparison of concentrations by process locations (averaged by plants) – MOUDI totals (Weight/Volume Air – µg/m3). ............................................................................................................. 54

Figure 8. Comparison of concentrations by process locations (averaged by plants) – PM2.5 fraction (Weight/Volume Air – µg/m3). ............................................................................................................. 55

Figure 9. Comparison of average concentrations: MOUDI totals and PM2.5 fractions – Inactive plant processes (Weight/Volume Air – µg/m3). ............................................................................................ 56

Figure 10. Comparison of average concentrations: MOUDI totals and PM2.5 fractions – Active plant processes (Weight/Volume Air – µg/m3). ............................................................................................ 57

Figure 11. Average representative PM2.5 fraction in percent of the MOUDI totals for inactive and active sample locations. Error bars represent one standard deviation. .............................................. 65

Figure 12a-b. Comparison of averages from MOUDI stages of all Inactive (3 samples, Fig. 12a) and Active (11 samples, Fig. 12b) sampling within the crusher process areas. .......................................... 79

Figure 13a-b. Comparison of averages from MOUDI stages of Plant A and Plant F (n=3 each) from the Active crusher areas of plant sampling. ......................................................................................... 80

Figure 14a-b. Comparison of averages from MOUDI stages of overall Inactive (3 samples) and Active (11 samples) concentrator areas of plant sampling. ................................................................. 81

Figure 15a-b. Comparison of averages from MOUDI stages of Plant A and Plant F (three samples each) from the Active concentrator areas of plant sampling. ............................................................. 82

Figure 16a-b. Comparison of averages from MOUDI stages of overall Inactive (3 samples) and Active (11 samples) agglomerator areas of plant sampling. ................................................................ 83

Figure 17a-b. Comparison of averages from MOUDI stages of Plant A and Plant F (three samples each) from the Active agglomerator areas of plant sampling. ............................................................. 84

Figure 18a-b. Comparison of averages from MOUDI stages of overall Inactive (3 samples) and Active (11 samples) kiln areas of plant sampling. ................................................................................ 85

NRRI/RI-2019/29 – Taconite Facilities Gravimetric Analysis ix

Figure 19a-b. Comparison of averages from MOUDI stages of Plant A and Plant F (three samples each) from the Active kiln areas of plant sampling. ............................................................................. 86

Figure 20. Particle size distribution related to multi-event comminution processes from inactive plants: Wt. % oversize versus undersize. ............................................................................................. 89

Figure 21. Particle size distribution related to multi-event comminution processes from active plants: Wt. % oversize versus undersize. ............................................................................................. 90

Figure 22. Particle size distribution ‘best-fit’ curve fitting - Cumulative fractions by weight oversize. ................................................................................................................................................ 91

Figure 23. Comparison of samples (averaged by location) by processing plant – MOUDI totals (Weight/Volume Air – µg/m3). ............................................................................................................. 95

Figure 24. Comparison of samples (averaged by location) by processing plant – PM2.5 fraction (Weight/Volume Air – µg/m3). ............................................................................................................. 96

LIST OF PHOTOS

Photo 1. 120 MOUDI II cascade impactor. .................................................................................................. 17

Photo 2. Total Filter Sampler (TFS). ............................................................................................................ 21

Photo 3. MOUDI sampler, TFS, and pump setup inside taconite processing facility. ................................. 24

Photo 4. Flagged-off sample site in potentially high-traffic corridor. ........................................................ 24

Photo 5. Sample holder tripod. ................................................................................................................... 26

LIST OF APPENDICES

Appendix A: Plant Sample Locations Appendix B: Plant Field Blank Gravimetric Analysis

NRRI/RI-2019/29 – Taconite Facilities Gravimetric Analysis 1

INTRODUCTION The Minnesota Taconite Workers Health Study (MTWHS) was initiated in 2008 and included a multicomponent study to further understand taconite worker health issues on the Mesabi Iron Range (MIR) in northeastern Minnesota. Approximately $4.9 million funding was provided by the Minnesota Legislature to conduct five separate studies related to this initiative, including: An Occupational Exposure Assessment, conducted by the University of Minnesota School of

Public Health (SPH); A Mortality (Cause of Death) study, conducted by the University of Minnesota SPH; Incidence studies, conducted by the University of Minnesota SPH; A Respiratory Survey of Taconite Workers and Spouses, conducted by the University of

Minnesota SPH; and An Environmental Study of Airborne Particulate Matter, conducted by the Natural

Resources Research Institute (NRRI) at the University of Minnesota Duluth (UMD). NRRI’s “Environmental Study of Airborne Particulate Matter” comprises a multi-faceted characterization of size-fractionated airborne particulate matter (PM) from MIR community “rooftop” locations, background sites, and all taconite processing facilities active between 2008 and 2014. Characterization includes gravimetric determinations, chemical characterization, mineralogical characterization, and morphological characterization. This report specifically discusses the methods and gravimetric results of multiple aerosol PM sample collections from active (operating) and inactive (temporarily, but completely, shut down) taconite plants on the MIR. Taconite plant samples were collected in 2009 and 2010. BACKGROUND Excessive exposures to various varieties of mineral dusts have an association with development of a wide variety of diseases including silicosis, coal workers pneumoconiosis, and asbestosis, lung cancer, and mesothelioma (Plumlee et al., 2006). Mesothelioma is a relatively rare cancer that develops in cells of the mesothelium, the protective lining around many of the internal organs of the body, and is most commonly attributed to exposure to asbestos (Fuhrer and Lazarus, 2011; Pass et al., 2004; Robinson et al., 2005). The Minnesota Department of Health Minnesota Cancer Surveillance System (MDH-MCSS) reported a 73% excess in mesothelioma cases relative to the rest of the state among northeastern Minnesota men between 1988 and 1996 (MDH-MCSS, 1999), causing concern that occupations associated with taconite mining may be fundamentally associated with the disease (Allen et al., 2015). Between 2002 and 2006, age-adjusted mesothelioma incidence amongst non-Hispanic white males was more than double that of the state rate for individuals in northeastern Minnesota, whereas mesothelioma incidence amongst non-Hispanic white females was approximately one-half the statewide rate for individuals in northeastern Minnesota (MDH-MCSS, 2012). An initial finding between 1988 and 2008 by the MDH identified 58 individuals with mesothelioma from an original cohort of 72,000 mine workers (MDH, 2007; MDH-MCSS, 2012). The initial MDH (2007) findings prompted the Minnesota Legislature to approve $4.9 million for the University of Minnesota SPH, University of Minnesota Medical School, and the NRRI to conduct a five-year comprehensive study on the possible cause(s) of this disease affecting taconite workers in northeastern Minnesota.

Identifying and characterizing what is in the air in both the communities and taconite plants within the study area is paramount to identifying potential mineral dust(s) and their source(s), either directly or indirectly responsible for the higher than normal incidence of this disease. The NRRI’s role in this study was to conduct a baseline environmental study, with an emphasis on characterizing airborne PM, including elongate mineral particles (EMPs) present in the PM, within five MIR communities, three background sites, and six taconite processing plants. Gravimetric, chemical, mineralogical, and morphological characterization was conducted within the NRRI study. The EMPs targeted in this study


comprise mineral particles that are of inhalable, thoracic, or respirable size and have a minimum aspect (length-to-width) ratio of 3:1 (Allen et al., 2015; Hwang et al., 2014; NIOSH, 2011).

It is important to note that the characterizations presented by the NRRI in this comprehensive study are merely snapshots of the ambient and micro-environmental concentrations taken within a three-year sampling period from strategic localities. While NRRI’s sampling is demonstrably representative of the environments being studied for purposes of characterization, the sampling methodologies and measurements are not meant to be equivalent with those performed by regulatory sampling, nor are the measurements intended to be used for the purpose of regulatory compliance or for deriving historical exposure estimates. Sample methodology and frequency are discussed in further detail below.

Although mesothelioma has been linked primarily to the inhalation of asbestos (Wagner et al., 1960), a comprehensive characterization of the ambient air PM is necessary for understanding all of the variables involved with this disease process. Taconite mining and processing activities in northeastern Minnesota can generate substantial amounts of mineral dust that may have the potential to produce adverse human health effects. This mineral dust—or PM—is made up of small particles that are generally micrometer (i.e., µm or micron) and sub-micrometer in size. In addition to mineral particles, the broader category of PM can also include organic dusts, chemicals, and even liquid droplets (Hinds, 1999). Particle size, mineralogy, morphology, and concentration dictate whether there is potential for adverse health effects (Gunter et al., 2007). Amphibole mineral species that have the potential to occur as asbestiform habit may be associated with increased risks for mesothelioma and other cancers. Amphibole mineralization is known to occur in rocks in northeastern Minnesota (French, 1968; Gunderson and Schwartz, 1962; McSwiggen and Morey, 2008; Wilson et al., 2008).

With respect to particle size, the United States Environmental Protection Agency (USEPA) is particularly interested in particles with aerodynamic diameters (Baron and Willeke, 2001) less than 10 µm (equivalent to PM10) because they can enter the human lung and potentially cause health issues. The PM10 can be further broken down into “inhalable coarse particles” that are less than 10 µm and “fine particles” that are less than 2.5 µm (ISO, 1995). The one-micrometer size (1 µm, PM1) is generally accepted as the distinction between the coarser dusts generated through mineral comminution processes and PM resulting from combustion (Hinds, 1999). Health effects from exposure to “fine” PM can lead to a variety of pulmonary and cardiovascular problems, including multiple types of cancer, when asbestiform particles are involved (Gunter et al., 2007). Reports from this study discuss the findings of airborne PM sampling in the MIR communities, background locations, and taconite plants. Companion reports are also available and include: Development of Standard Operating Procedures (SOP) for Particle Collection and Gravimetric Analysis (Monson Geerts et al., 2019a); Mesabi Iron Range Community Particulate Matter Collection and Gravimetric Analysis (Monson Geerts et al., 2019b); A Characterization of the Mineral Component of the Particulate Matter (Monson Geerts et al., 2019c); and Elemental Chemistry of the Particulate Matter (Monson Geerts et al., 2019d). In addition, a report focusing on the collection and analysis of EMPs in age-dated lake sediments on the MIR (Zanko et al., 2019) is also available. What is Mesothelioma?

The aggressive type of cancer known as mesothelioma is rare and most commonly results from malignancy of mesothelial cells of the pleural (outer lung lining) and peritoneal (abdominal cavity lining) tissues (Fuhrer and Lazarus, 2011). The disease is nearly always fatal and has been linked to the exposure of asbestos and other mineral fibers (via inhalation) (IOM, 2006; NIOSH, 2011; Robinson et al., 2005; Wagner et al., 1960). Following diagnosis, median survival is commonly 9 to 12 months. Male rates for mesothelioma are considerably higher than female rates, and rates of the disease are higher in industrialized countries relative to non-industrialized countries (Robinson et al., 2005, and references therein).


While there is much debate and research on the specific minerals that may be responsible for mesothelioma, recommendations by the National Institute for Occupational Safety and Health (NIOSH) have resulted in regulations through other government agencies concerning six minerals as described in the description of a “covered” mineral below:

“NIOSH considers asbestos to be a “Potential Occupational Carcinogen”* and recommends that exposure be reduced to the lowest feasible concentration. The NIOSH recommended exposure limit (REL) for airborne asbestos fibers and regulated EMPs is 0.1 countable EMP from one or more covered minerals per cubic centimeter, averaged over 100 minutes, where: a “Countable” elongate mineral particle (EMP) is any fiber or fragment of a mineral

longer than 5 µm with a minimum aspect ratio of 3:1 when viewed microscopically with use of NIOSH Analytical Method 7400 (“A” rules) or its equivalent; and

a “Covered” mineral is any mineral having the crystal structure and elemental composition of one of the asbestos varieties (chrysotile, riebeckite asbestos [crocidolite], cummingtonite-grunerite asbestos [amosite], anthophyllite asbestos, tremolite asbestos, and actinolite asbestos) or one their nonasbestiform analogues (the serpentine minerals antigorite and lizardite, and the amphibole minerals contained in the cummingtonite-grunerite mineral series, the tremolite-ferroactinolite mineral series, and the glaucophane-riebeckite mineral series).

This clarification of the NIOSH REL for airborne asbestos fibers and related EMPs results in no change in counts made, as defined by NIOSH Method 7400 (‘A’ rules). However, it clarifies definitionally that EMPs included in the count are not necessarily asbestos fibers” (NIOSH, 2011). Other minerals have been documented to date for which exposure has been linked to

mesothelioma, although these minerals are not currently regulated. They include, but are not limited to, the following: winchite and richterite (two amphiboles indicated in Libby, MT study cases (Gunter et al., 2007; Wylie and Verkouteren, 2000), balangeroite (Compagnoni et al., 1983; Turci et al., 2009), and erionite (a zeolite mineral: Carbone et al., 2011; NTP, 2014; Wagner et al., 1985).

Recent meta-analysis of epidemiological data suggests different toxicities exist, depending on mineral type and dimensions (Berman and Crump, 2008; P. Cook (USEPA), 2010, pers. comm.). However, due to past confusion in the research over mineralogical, morphological, and dimensional details surrounding possible causes of disease, NIOSH developed its Roadmap publication (2011) as a strategy for facilitating future research. One component of the NIOSH Roadmap expanded the definition of “asbestos” to include both asbestos fibers and all other related morphologies, including cleavage fragments, in their recommended exposure limits (REL). This action was done primarily to facilitate research to better understand the mineralogical, morphological, and dimensional details in predicting asbestos-related disease as well as reduce exposures to the lowest feasible concentrations. Due to the difficulties of applying current descriptive terminology to PM of micrometer scale (e.g., the mineralogical definition of asbestiform, which Gunter et al. (2007) state should be reserved for amphiboles that split lengthwise), the NRRI’s study will refer to all particles with an aspect ratio ≥ 3:1 as EMPs. See also Appendix G (glossary) of the SOP report (Monson Geerts et al., 2019a). REGULATION CONCERNING PARTICULATE MATTER (PM) As the USEPA states, “The Clean Air Act identifies two types of national ambient air quality standards. Primary standards provide public health protection, including protecting the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.” (https://www.epa.gov/criteria-air-pollutants/naaqs-table) *NIOSH’s use of the term “Potential Occupational Carcinogen” dates to the OSHA classification outlined in 29 CFR 1990.103 and, unlike other agencies, is the only classification for carcinogens that NIOSH uses (OSHA, 1990).

https://www.epa.gov/criteria-air-pollutants/naaqs-table


The Minnesota Pollution Control Agency (MPCA) has summarized the Clean Air Act regulation of particulate matter as follows (https://www.pca.state.mn.us/air/fine-particle-pollution):

“The Clean Air Act regulates two sizes of particulate matter: PM2.5 (fine particles) and PM10. PM2.5 includes particulate matter that is less than 2.5 microns in diameter; PM10 includes all particulate matter less than 10 microns in diameter (including PM2.5). The USEPA sets National Ambient Air Quality Standards (NAAQS) for both PM2.5 and PM10, including both primary standards to protect public health and secondary standards to protect the environment.

In 2012, the USEPA reviewed the science related to the health and environmental impacts of particulate matter and revised the NAAQS to reflect the most up-to-date information. The level of the current primary and secondary daily fine particle [PM2.5] standard is 35 µg/m3 and the primary annual standard is 12 µg/m3. The primary and secondary daily PM10 standard is 150 µg/m3.”

The USEPA’s NAAQS standards for PM2.5 and PM10 are summarized in Table 1. Table 1. NAAQS for PM2.5 and PM10 (Source: https://www.epa.gov/criteria-air-pollutants/naaqs-table).

Pollutant Primary/ Secondary

Averaging Time Level Form

Particle Pollution (PM)

PM2.5

primary 1 year 12.0 µg/m3 Annual mean, averaged over 3 years

secondary 1 year 15.0 µg/m3 Annual mean, averaged over 3 years

primary and secondary 24 hours 35 µg/m3 98th percentile, averaged over 3 years

PM10 primary and secondary 24 hours 150 µg/m3 Not to be exceeded more than once

per year on average over 3 years

NOTE: The USEPA revoked the annual PM10 NAAQS in 2006 (which had been 50 µg/m3), so only the 24-hour standard of 150 µg/m3 currently applies (USEPA, 2013). For workplace indoor air quality, the Occupational Safety Health Administration (OSHA) enforces air quality regulations. For workplace indoor air quality at mining operations and mineral processing facilities, the Mine Safety and Health Administration (MSHA) enforces air quality regulations.

Without specificity to the mineralogy of the PM, the overall weight (OSHA – total dust 15 mg/m3 and PM10 5 mg/m3) per volume air can be compared with exposure limits and recommendations set by regulators provided that sampling methods are consistent with local, state, and federal guidelines. Typically, these exposure limits are expressed as eight-hour time-weighted averages. For example, OSHA has a permissible exposure limit (PEL) regulation regarding general PM other than coal, silica, or asbestos, which is directed at respirable particles less than 10 µm in size that are not otherwise regulated, of 5,000 µg/m3 (5 mg/m3). The American Conference of Governmental Industrial Hygienists (ACGIH) 2001 TLV® (threshold limit value; ACGIH, 2001) recommends a limit of 3,000 µg/m3 (3 mg/m3) for PM. In general, MSHA has adopted the regulations set by OSHA 1910.1000 Limits for Air Contaminants (OHSA, 1997).

Keep in mind that these limits and/or recommendations decrease with an increase in the percent of silica (SiO2) content and/or the presence of asbestos fibers, both of which are separately regulated based on specific analytical methods. This may be an issue in certain areas of Minnesota’s taconite processing facilities, depending on the overall mineralogy of the rocks being mined, and the mineral processing that takes place to produce the taconite pellets (see generalized process flow diagrams – Fig. 1; USEPA, 2001; 2003). For instance, crushing operations are likely to have higher silica

https://www.pca.state.mn.us/air/fine-particle-pollution

https://www.epa.gov/criteria-air-pollutants/naaqs-table


concentrations than other process operations because the dust generated during this process is from the raw, silica-containing ore prior to magnetic separation and associated magnetic iron concentration. Magnetic separation removes the magnetic iron oxide ore minerals (primarily magnetite; Fe3O4) from other non-magnetic gangue minerals contained in the ore. This process is wet and is likely to generate low concentrations of silica dust.

During agglomeration, a clay component (bentonite, which is an aluminum phyllosilicate) is added to the iron oxide concentrate to make “green balls,” which are unfired taconite pellets. There may also be increased amounts of silica in areas such as the agglomerators/balling drums because of this clay addition. Limestone containing calcite (CaCO3) and/or dolostone containing dolomite (CaMg(CO3)2) may also be added during the production of flux pellets; therefore, dusts containing carbonate minerals may also be present in the agglomerator/balling drum areas. In the vicinity of the kiln/pellet discharge, silica dust may also be present as a result of liberation of silica from the taconite pellets during movement within and immediately after heating in the kiln (Fig. 1).


Figure 1. Generalized taconite processing flow diagram (USEPA, 2001).


Figure 1 (continued).


OBJECTIVES In response to the Minnesota Legislature bill H.F. 3569 (Minnesota Legislature, 2008), the University of Minnesota SPH and the NRRI at UMD conducted a multi-component study (the MTWHS) related to physical, mineralogical, and chemical attributes of mineral dust (NRRI) and taconite workers’ health (University of Minnesota SPH) based on specific attributes of mineral dust present in industrial and public settings on Minnesota’s MIR. NRRI’s role in the MTWHS includes measurement and characterization of airborne PM in the MIR communities, taconite processing plants, and background locations. Although the emphasis of the research is focused on possible links to the elevated number of cases of mesothelioma and other cancers in taconite workers (Allen, 2014; Allen et al., 2015; Lambert et al., 2013; MDH, 2003; MDH, 2007; MDH-MCSS, 1999; MDH-MCSS, 2012), it is imperative that a comprehensive characterization of the PM in both community and plant environments be conducted. A comprehensive characterization (concentrations, morphological characteristics, mineralogical attributes, and chemical compositions), as well as identification of possible sources of ambient PM in the communities and plants, may provide important data to increase our understanding of air quality as related to PM on the MIR and may aid in developing means to address overall air quality. Although specific concentrations of PM have not been associated with or linked to mesothelioma, this component of the comprehensive characterization of the ambient PM on the MIR will be addressed. This report discusses the gravimetric characteristics of PM within the six MIR taconite producing plants. Questions to be addressed How much airborne PM is present (concentrations) in specific ore processing areas of the

taconite processing plants? Do these PM concentrations change depending on whether the plant is inactive or active?

Do PM concentrations change with respect to the different process locations within a plant? Are these same relative amounts of PM in the specific process locations present in all six taconite processing plants on the MIR? Can the levels of PM in the general process areas be ranked from lowest to highest with statistical significance?

Does the size-fractionated method of sampling (MOUDI) indicate whether the concentrations and proportions of PM change within the plants?

Are there any relationships in the concentration or size distribution of PM due to the geographical location of the mine/plant on the MIR?

What further work is warranted as a follow-up to this study component?

To address the general question “What is in the air?”, a the NRRI has conducted a multifaceted sampling program involving both: 1) size-fractionated PM sampling; and 2) total filter sampling at each sampling location. Size-fractionated PM sampling allows for the determination and evaluation of various PM designations and was completed using a Micro-Orifice Uniform Deposit Impactor (MOUDI) II Model 120 sampler (Marple et al., 1991; 2014). This 10-stage cascade impactor sorts the PM with respect to nominal aerodynamic diameter cut sizes of: 10 µm, 5.6 µm, 3.16 µm, 1.8 µm, 1.0 µm, 0.56 µm, 0.32 µm, 0.18 µm, 0.10 µm, and 0.056 µm, plus an initial cut of 18 µm, and an after-filter below the impaction stages that collected material with an aerodynamic diameter less than 0.056 µm. This comprehensive type of sampling allowed for the calculation (and graphical depiction) of particle mass concentrations by size and long-term averages by stage, as well as for different aerodynamic diameter particles. The MOUDI provided the study with a degree of size and gravimetric detail that would not be possible using more conventional PM samplers.


SAMPLING METHODOLOGY The emphasis of this study was on the characterization of EMPs within the collected PM; however, a comprehensive characterization of the PM was also essential. Specific objectives associated with the aerosol sampling of PM in the taconite processing plants included: 1) gravimetric analysis of PM and comparisons between taconite plants; 2) comparisons of PM concentrations, when possible, between inactive and active plant operation; 3) comparisons between the process areas within a plant as well as between plants; and 4) comparisons of plant PM concentrations and characteristics across the MIR (Fig. 2, right side) with respect to their spatial (geographic) relationship to the area’s geology (Table 2), especially between the non-thermally metamorphosed BIF in the western MIR, to that of thermally metamorphosed BIF in the east (Fig. 3). Table 2. The taconite mining companies and their corresponding processing facilities that participated in this study. Generalized geographic locations are determined based on the location of the mine pit for the plant relative to the metamorphic Zone 2–Zone 3 mineralogical boundary as indicated by French (1968) and McSwiggen and Morey (2008).

MINING COMPANY TACONITE PROCESSING FACILITY GENERALIZED GEOGRAPHIC LOCATION

U.S. Steel Keewatin Taconite (Keetac) West

Arcelor Mittal Cliffs Natural Resources

U.S. Steel Hibbing Taconite (Hibtac) West

U.S. Steel Minnesota Taconite (Minntac) West

Cliffs Natural Resources United Taconite (Utac) West

Arcelor Mittal Minorca West

Cliffs Natural Resources Northshore East


Sampling Locations

Figure 2. Study area sampling locations. MIR community sampling occurred in Keewatin, Hibbing, Virginia, Babbitt, and Silver Bay. Background community sampling took place in Ely, Duluth, and Minneapolis (see left side of figure). Taconite processing plants that were also sampled during the NRRI’s PM characterization studies included Keetac, Hibtac, Minntac, Utac, Minorca, and Northshore (right side of figure).


Figure 3. Locations of taconite plants and communities on the MIR with respect to the BIF (brown-red color), the geological unit mined for iron on the Mesabi Range. Metamorphic zones 1, 2, 3, and 4 refer to different mineralogical zones associated with the BIF that were identified by French (1968) and further refined by McSwiggen and Morey (2008). These zones indicate the mineralogical changes occurring in the BIF progressing along strike from west to east. Mineralogical changes in zones 3 and 4 were the result of thermal metamorphism of the BIF during intrusion of Duluth Complex-related magmas ~1.1 billion years ago. The mineralogical characteristics of these zones are summarized below the map.

Zones 3 and 4: quartz, magnetite, grunerite, hornblende, hedenbergite, ferrohypersthene (ferrosilite), and fayalite

Zones 1 and 2: quartz, magnetite, hematite, carbonates, talc, chamosite, greenalite, minnesotaite and stilpnomelane

Biwabik Iron Formation Mineralogy

West to East


Preliminary Statistical Analysis Unlike NRRI’s sampling plan for the MIR communities (Monson Geerts et al., 2019a), which utilized previous PM sampling and EMP analyses by state regulatory agencies to statistically calculate the number of samples needed for characterization, the taconite plant sampling plan was generated based on the consistency of the geology and process technologies of mining the BIF. Based on geologic and process technology studies mentioned in the following section, there is no apparent difference between the mineralogy of the western BIF throughout Zone 1 of the MIR (Fig. 3) or taconite plant processes in this part of the MIR, therefore lending to the statistical power necessary to evaluate PM using the 10 samples collected by the NRRI from the five plants at a seemingly 90% confidence level. This confidence level was calculated using a multivariate comparison among the five plants and was performed using variables of log10 PM1, log10 PM2.5, log10 PM10, and log10 coarse mode. Table 3 gives the p-values from different test methods used. The null hypothesis of a multivariate test is that: treatments have equal mean vectors (here we used the word “vectors” rather than “values” because we are using multiple variables for each treatment to do the comparison). A p-value that is greater than 0.05 equates to the acceptance of the null hypothesis. Since our test results show that p-values are greater than 0.05 by the three test methods, we can say there is no significant difference among these five plants for PM concentrations. Therefore, these plants were grouped together to gain statistical power in evaluating their PM. Table 3. P-values from multivariate comparisons among the five plants in the western MIR (Zone 1).

Multivariate test method p-value

Wilks 0.1017

Pillai 0.1059

Hotelling-Lawley 0.0971

Because of the relatively low number of samples collected, caution must be used when evaluating and comparing the data, especially in smaller subsets of data that may not have the statistical power of all samples used together. In these comparisons, it will be noted that interpretations are based on educated speculation rather than statistical significance. STUDY AREA The corresponding study area, including the five MIR communities, two background sites, and the six taconite processing plants, is located in northeastern Minnesota (Figs. 2 and 3). The Minneapolis background site was added for comparative purposes as a large urban center. The community and background site gravimetric data are discussed in greater detail in Monson Geerts et al. (2019b). Regional Geology The MIR is approximately 120 miles long and averages up to two miles in width. Rocks that make up this range comprise the Paleoproterozoic Animikie Group, which is composed of three major geological formations. These include: 1) the Pokegama Formation (also known as the Pokegama Quartzite), which comprises an upper member of orthoquartzite, a middle member of interbedded siltstone and shale, and a lower member of shale with interbedded siltstone; 2) the BIF, a 175- to 300-foot-thick sequence of iron-rich sedimentary rocks that has historically been subdivided into four informal members including, from bottom to top, the Lower Cherty Member, the Lower Slaty Member, the Upper Cherty Member, and the Upper Slaty Member; and 3) the Virginia Formation, a sequence of argillite, sandstone, and graywackes at least 600 feet thick that makes up the top of the Animikie Group. These three formations generally strike in a northeast-southwest direction, but locally, strikes oriented south-southwest to


north-northeast occur in the vicinity of the Virginia Horn (Fig. 3). On the MIR, these three formations typically have relatively shallow dips ranging from 3 to 15 degrees, with the steepest dips occurring in the easternmost MIR adjacent to the Duluth Complex (Severson, 2012). Southwick et al. (1988) and Ojakangas (1994) suggest that the Animikie Group sedimentary strata were deposited in a continental shelf environment in a shallow sea that formed in a northward-migrating foreland basin that developed in response to compressional tectonic activity to the south during the Penokean Orogeny (1880–1830 Ma; Schulz and Cannon, 2007).

To the east, the Animikie Group sedimentary strata are in contact with the Duluth Complex, which is composed of a series of mafic (iron- and magnesium-rich igneous rocks containing 45%–52% SiO2 (LeBas et al., 1986; LeBas and Streckeisen, 1991)) and locally ultramafic igneous intrusive rocks (generally magnesium-rich igneous rocks containing less than 45% SiO2 (LeBas et al., 1986; LeBas and Streckeisen, 1991)). Details regarding the specific intrusions and rock types that comprise the Duluth Complex can be found in Miller et al. (2002). The ~1.1-billion-year-old Duluth Complex provided heat that resulted in local thermal metamorphism of the BIF, altering its mineral, chemical, and physical characteristics (French, 1968; McSwiggen and Morey, 2008; Severson et al., 2009). The mineralogy of the BIF is an important underlying control on the composition of the dust produced at MIR taconite operations. Although stratigraphic units were initially named and identified locally in different geographic regions of the MIR, the submembers of the BIF being mined were correlated and are, for the most part, mineralogically redundant across the western three-quarters of the MIR (Severson et al., 2009). However, mineral changes first begin to occur locally in the eastern quarter of the BIF as a result of contact (thermal) metamorphism (Severson, 2012). These mineralogical changes occurred 1.1 billion years ago during the emplacement collectively known as the Duluth Complex. Heat associated with this event raised the temperature of the BIF, with the easternmost parts of the BIF attaining the highest temperatures. The thermal metamorphism caused primary iron-formation minerals to react to locally form new suites of iron-rich phyllosilicate minerals (zones 1 and 2: i.e., stilpnomelane, minnesotaite, greenalite, etc.) and, in the easternmost parts of the BIF, iron-rich amphiboles and pyroxenes (zones 3 and 4). The amphiboles are principally of the cummingtonite-grunerite series along with actinolite and hornblende (French, 1968; Ross et al., 1993). Mineralogy, morphology, and EMP dimensions are discussed in greater detail below and in Monson Geerts et al. (2019c). In Figure 3, the brownish-red colored geological unit is the BIF, the geological unit that is the source of the iron ore mined on the Mesabi Range. Metamorphic Zones 1, 2, 3, and 4 refer to different mineralogical zones associated with the BIF that were identified by French (1968) and further refined by McSwiggen and Morey (2008). These zones identify distinct mineral assemblages that occur in the BIF along strike from west to east. These distinct mineral assemblages resulted from thermal metamorphism of the BIF by the intrusion of Duluth Complex-related magmas approximately 1.1 billion years ago (French, 1968; McSwiggen and Morey, 2008; and others). The mineralogy of the different zones reflects occurrences of amphiboles towards the contact with the intrusive rocks that have been identified in zones 3 and 4 (Fig. 3; French, 1968; McSwiggen and Morey, 2008). Taconite Mines and Processing Plants In general, the processes within the six taconite ore processing plants in northeast Minnesota are essentially the same (Zanko et al., 2007; 2010), although minor differences may be present in specific processes and equipment used. These differences mostly reflect the age of specific plants. Particulate matter emissions within these plants may vary substantially and are directly related to—and change with respect to—the location within the ore process sequence. Particulate matter levels within the plants are controlled by a variety of devices, including, but not limited to: cyclones, multi/rotoclones, wet scrubbers, bag houses, electrostatic precipitators, and water sprays.


According to the USEPA (1997), the largest source of PM emissions in taconite ore mines comes from traffic on unpaved haul roads. Wind erosion on unpaved road surfaces and non-vegetated waste rock and tailings basins can also contribute substantial amounts of PM emission at taconite mines. The USEPA also states that although blasting is a notable source of the various size fractions of PM, it is a short-term event, and most materials settle quickly (Richards and Brozell, 2001; USEPA, 1997). Sampling of taconite processing facilities began in March 2009 and continued until June 2010, after a total of 14 sample sets were collected. These sampling events included at least one ‘active’ (while plant processes were operating) sample set from each facility. During this 15-month period, economic uncertainty in the global economy resulted in several plant shutdowns and made it possible to obtain PM samples during periods of mine/plant inactivity (‘inactive’). Although samples from inactive periods of all of the plants would have been optimum, the NRRI was able to collect ‘inactive’ samples from three of the six processing facilities. These ‘inactive’ samples were used to establish ‘background’ values within the plants.

Plant A Active Calculations

Active Crusher Stage Percent 1 Percent 2 Percent 3 High Low Average

0 17.92 8.02 14.34 17.92 8.02 13.43 1 14.8 11.65 13.06 14.8 11.65 13.17 2 14.92 11.32 12.98 14.92 11.32 13.07 3 17.77 9.26 12.36 17.77 9.26 13.13 4 12.88 10.56 13.96 13.96 10.56 12.47 5 7.44 9.36 10.11 10.11 7.44 8.97 6 4.44 8.98 6.9 8.98 4.44 6.77 7 2.21 7.56 4.47 7.56 2.21 4.75 8 2.01 5.94 3.68 5.94 2.01 3.88 9 2.23 6.86 2.93 6.86 2.23 4.01

10 2.04 6.32 2.6 6.32 2.04 3.65 F 1.34 4.17 2.61 4.17 1.34 2.71

Active Concentrator Stage Percent 1 Percent 2 Percent 3 High Low Average

0 39.89 20.58 36.04 39.89 20.58 32.17 1 25.96 14.56 16.28 25.96 14.56 18.93 2 10.85 10.83 10.73 10.85 10.73 10.80 3 6.7 8.71 6.53 8.71 6.53 7.31 4 2.7 7.24 4.8 7.24 2.7 4.91 5 2.13 5.83 3.77 5.83 2.13 3.91 6 2.28 5.73 4.27 5.73 2.28 4.09 7 1.86 4.62 3.57 4.62 1.86 3.35 8 1.72 4.9 4.23 4.9 1.72 3.62 9 2 4.42 3.44 4.42 2 3.29

10 2.33 4.11 3.3 4.11 2.33 3.25 F 1.58 8.47 3.04 8.47 1.58 4.36


Active Agglomerator Stage Percent 1 Percent 2 Percent 3 High Low Average

0 54.4 70.92 54.82 70.92 54.4 60.05 1 23.94 12.35 17.41 23.94 12.35 17.90 2 13.6 6.68 12.66 13.6 6.68 10.98 3 2.4 4.36 8.58 8.58 2.4 5.11 4 1.23 1.77 2.15 2.15 1.23 1.72 5 0 0.84 0.63 0.84 0 0.49 6 0.67 0.54 0.59 0.67 0.54 0.60 7 0.47 0.79 0.83 0.83 0.47 0.70 8 1.46 0.7 1.55 1.55 0.7 1.24 9 0.88 0.36 0.37 0.88 0.36 0.54

10 0.49 0.26 0.2 0.49 0.2 0.32 F 0.46 0.43 0.21 0.46 0.21 0.37

Active Kiln Stage Percent 1 Percent 2 Percent 3 High Low Average

0 29.63 32.38 39.47 39.47 29.63 33.83 1 33.8 37.35 34.16 37.35 33.8 35.10 2 22.99 12.13 15.37 22.99 12.13 16.83 3 8.55 7.74 4.34 8.55 4.34 6.88 4 2.49 3.92 2.97 3.92 2.49 3.13 5 0.86 2.55 1.46 2.55 0.86 1.62 6 1 1.5 0.79 1.5 0.79 1.10 7 0.2 0.58 0.36 0.58 0.2 0.38 8 0.15 0.57 0.31 0.57 0.15 0.34 9 0.08 0.49 0.22 0.49 0.08 0.26

10 0.09 0.38 0.21 0.38 0.09 0.23 F 0.16 0.41 0.34 0.41 0.16 0.30

For statistical purposes, two of the six taconite processing facilities, e.g., Plant A and Plant F – to be discussed in detail below, were chosen to be sampled three times during ‘active’ operation. One of these two plants was located on the eastern half of the MIR within the thermally metamorphosed Zones 3 and 4 (French, 1968; McSwiggen and Morey, 2008) as shown in Figure 3. The Plant A facility fills this role because it processes ore mined from the most thermally metamorphosed zone of the iron-formation, Zone 4, where amphibole minerals are present. The second plant, Plant F, is located centrally or on the western half of the MIR, where contact metamorphic effects resulting from the Duluth Complex are not recognized, i.e., unmetamorphosed Zone 1 (French, 1968; McSwiggen and Morey, 2008).

Four sample locations within each of the taconite processing facilities were selected. The same process areas were sampled in each plant to allow plant-by-plant comparisons. These sampling locations were chosen because they represent process areas where significant changes in size and/or mineralogical characteristics occur. The four process areas sampled in each of the taconite facilities included: 1) fine crusher; 2) concentrator – magnetic separator; 3) agglomerator – balling drums/discs, and 4) kiln – pellet discharge. Facilities that were sampled multiple times were consistently sampled in the exact same location during the multiple sampling events.


Geology, Taconite Process Technology, and Sampling Numbers Because of geological consistency within the “western” three-quarters of the BIF (Zone 1) French, 1968; McSwiggen and Morey, 2008 – see Fig. 3), the processing technologies and their relative levels of PM generation are comparable. Five of the six taconite mine/plants are located within this metamorphic zone of the MIR, including (from west to east): Keetac, Hibtac, Minntac, Utac, and Minorca. These consistencies have been described in studies focused on mineralogy and microscopic evaluations of coarse tailings from Minnesota taconite operations (Zanko et al., 2007; 2010). However, both mineralogical and physical differences in the BIF are documented in the “eastern” quarter of the MIR (metamorphic Zone 4) (French, 1968; McSwiggen and Morey, 2008 – see Fig. 3), which was affected by thermal metamorphism during the emplacement of intrusive rocks of the Duluth Complex. Mineralogical changes (Monson Geerts et al., 2018c), as well as an increase in the compressive strength and changes to the crystallinity and grain size of the rock, have the potential to affect the amount, size, and chemistry of PM generated. However, once the process stream is past the concentration/magnetic separation stage, the composition of the materials in subsequent stages of processing within all of the plants is, for the most part, mineralogically the same. Based on the above considerations, a characterization sampling plan was devised for the taconite processing plants using: guidance from collaborators Virgil Marple and Dale Lundgren (particle scientists from the

University of Minnesota and University of Florida, respectively); a phased approach by continually comparing early NRRI plant sampling PM data and EMP

analysis averages and variability; and limitations due to overall budget.

Each of the six plants was sampled a minimum of once during active operation and once during total inactivity, if the occasion arose. Two of the plants were sampled a minimum of three times during active operation, including: 1) Plant A; and 2) Plant F, in order to compare differences between ore influenced by thermal metamorphism. Thus, assuming there is little to no difference in the mineralogical composition of the BIF, a minimum number of 7–10 samples from the five plants to the west would be sufficient to obtain statistical power at a 90% confidence level (see statistical analyses). A series of samples was collected during each sample event, including samples at each of the four major process locations indicated above, including: 1) secondary crusher; 2) magnetic separator and concentrator; 3) agglomerator; and 4) kiln pellet discharge. Again, these four process sampling locations were considered demonstrably representative of the environments being studied for purposes of characterization. For additional information regarding the sampling plan, see Monson Geerts et al. (2019a). PARTICULATE MATTER SAMPLING In order to spatially, gravimetrically, mineralogically, and chemically characterize PM, the NRRI used three MSP second-generation micro-orifice uniform deposit impactors (120 MOUDI II) for the collection of size-fractionated PM (see http://www.mspcorp.com/ for more details). The equipment and methods used by the NRRI to characterize PM in the taconite plants were consistent throughout the sampling collection period. Performance and precision of the MOUDI instruments were tested in a USEPA-approved aerosol test chamber and shown to be consistent (Marple et al., 2014; Monson Geerts et al., 2019a). Application of the MOUDIs for long-term ambient sampling was also demonstrated by comparing size distributions (average PM2.5 and PM10) from the three background sites, which compare well with three-year averages over the same period conducted by state regulatory sampling (MPCA, 2013).

http://www.mspcorp.com/


120 MOUDI II Cascade Impactor The three 10-stage MOUDI II – model 120 cascade impactors utilized in this study are equipped with internal stepper-motor stage rotation to provide uniform particle deposition on collection substrates. These samplers are designed for precision, high-accuracy sampling (based on a flow rate of 30 L/min.) within a PM cut-size range from 18 µm to 0.056 µm (Photo 1). This size-fractionating of the aerosol particles allows for the designation of the PM into specific size classifications including: PM1, PM2.5, and PM10, which is part of the characterization as well as important for assessing mass weight. Table 4 indicates the MOUDI stages and size ranges based on aerodynamic diameter and log mean diameter. Based on the distribution of PM of various aerodynamic diameters collected by the MOUDI sampler, PM size fractions can be subdivided into which area of the human respiratory system they would affect (refer to right side of Table 4; Marple, 2010, pers. comm.). A number of particle collection experiments using the MOUDI were conducted prior to the formal sampling program (Monson Geerts et al., 2019a). These experiments were completed to determine an adequate run-time to collect a sufficient weight of PM for gravimetric, chemical, mineralogical, and morphological characterization. Because of relatively high concentrations of mineral PM in the plants, specifically the agglomerator and kiln, it was determined that the optimal particle sample run times for all four process locations within the plants be two hours. This sample time was favorable in depositing sufficient PM (but not too much) that could easily be gravimetrically analyzed. An additional 15-minute sample (partial MOUDI) was also collected for optimizing analysis using a scanning electron microscope (Table 5). Both the MOUDI and the total filter sampler (TFS) were set up to collect samples at each plant process location.

Photo 1. 120 MOUDI II cascade impactor.


Table 4. MOUDI cascade impactor stages, ranges, and PM designations.


Table 5. Fifteen-minute partial MOUDI stages and particulate matter ranges.


Respirable Weight Fraction PM2.5 The MOUDI cascade impactor fractionation is based primarily on the PM10 and PM1 cut sizes; therefore, it does not have a specific cut-size of PM2.5. However, a simple formula can be used to calculate the PM2.5 fraction from the ranges of particle sizes that are collected (B. Olson, 2011, pers. comm.,) as follows:

PM2.5 = (SUM of MOUDI Stages 5-F) + MOUDI Stage 4 x [(LOG (2.5 ÷ 1.78)) ÷ (LOG (3.16 ÷ 1.78))] All MOUDI stage measurements in concentrations (µg/m3)

where F = after filter stage The PM2.5 fraction represents all of the PM with an aerodynamic size less than 2.5 µm. This would essentially include all of the particles impacted on MOUDI stage 5 and below and also include some of the particles on stage 4 (Table 3). This size fraction is commonly known as the “respirable fraction,” including PM small enough to affect tracheal, bronchial, bronchiolar, and alveolar regions of the human body (USEPA, 1997). Total Filter Sampler (TFS) The MOUDI cascade impactor was accompanied at each sample location by a TFS. Filter substrates from the TFS are utilized for mineralogical and chemical analysis. The TFS sampler is simply designed, with no moving parts or electrical components (Photo 2). A mixed cellulose ester (MCE) filter substrate is placed in the holder of the TFS apparatus by screwing the two halves of the TFS filter holder together. The smaller-diameter outlet tube of the sampler is connected to a rotameter, which is then attached to the vacuum pump. The rotameter is utilized to adjust the pump volume to the desired vacuum to establish a flow rate of 8 L/min. The setup procedures of both samplers are described in greater detail in Monson Geerts et al. (2019a). Consistency in sample collection by the two methods was checked gravimetrically by comparing the total mass of PM on MOUDI substrates with the total mass of PM on the TFS at each location. Due to their instabilities, gravimetric determination of the MCE filter has been shown to be problematic for masses lower than 200 µg (Bogen et al., 2011). Since the variation in MCE mass as a function of temperature and humidity is independent of the mass of deposit on the filter, the larger the mass of deposit on the filter, the smaller the relative effect of MCE mass variation, and thus, the better the correlations. Since most of the TFS MCEs from the plants contained >200 µg, the practice of weighing them was still conducted and found useful in this study for NRRI internal comparative purposes only. When compared in linear space, a one-to-one plot of the data (Fig. 4) reveals a significant correlation of particle mass per volume of air between the two samplers. In fact, it appears that below the 200 µg cutoff the significance between the two sample totals starts to digress. The flow-weighted data were also used in a statistical regression analysis that produces an (R2) correlation of 0.89 that was calculated at a 95% confidence level (Table 6). Both of these evaluations indicate a strong correlation and level of agreement achieved for the collection of aerosol PM by these two methods.


Photo 2. Total Filter Sampler (TFS).

Figure 4. X/Y plot of plant concentrations – MOUDI totals with Total Filter counterparts in Weight/ Volume Air (µg/m3).

10 100 1000 10000 100000

MOUDI Total - [Weight / Volume Air (µg/m3)]

10

100

1000

10000

TFS

- [W

eigh

t / V

olum

e A

ir (µ

g/m

3 )]

Comparison of Inplant MOUDI Totals and TFS Total Particulate Matter


Table 6. Regression analysis comparing MOUDI totals with TFS weights in two-hour sample.

Regression Statistics

Multiple R 0.9460 R Square 0.8948 Adjusted R Square 0.8929 Standard Error 1513.1938 Observations 55 ANOVA

df SS MS F Significance F

Regression 1 1.03E+09 1.03E+09 4.51E+02 1.38E-27 Residual 53 1.21E+08 2.29E+06 Total 54 1.15E+09

Coefficients Standard Error t Stat P-value Lower 95% Upper

95% Lower 95.0%

Upper 95.0%

Intercept 192.7785 236.8870 0.8138 0.4194 -282.3568 667.9137 -282.3568 667.9137 X Variable 1 1.0789 0.0508 21.2365 0.0000 0.9770 1.1808 0.9770 1.1808

Substrates and associated analyses Different types of impaction substrates and filters that are typically used in the collection of aerosol PM were evaluated to identify the best material for both gravimetric and analytical procedures (Monson Geerts et al., 2019a). Because the particle deposition across the range of MOUDI cut sizes will be used to determine mass distribution, the substrate materials that are most ideal for use in the MOUDI are those that have a low mass and a stable tare weight. For gravimetric analysis, both test results (Monson Geerts et al., 2019a) and references (Marple et al., 1991) concluded that the optimum substrates for impaction surfaces within the MOUDIs are polycarbonate (PC) and a Teflon® after filter. The Teflon® after filter’s associated low-pressure drop property helps to reduce the size of the vacuum pump needed to maintain 30 L/min flow rate in the MOUDI. Each MOUDI sample set consists of a “Series” of 11 PC substrates and one Teflon® after filter. The MCE filter was specifically chosen for utilization in the TFS sampler because it allows high-volume collection and analysis of mineral PM using indirect methods for TEM analysis. Table 7 lists substrates and filters that were utilized for various analytical procedures within this study.


Table 7. Substrate and filter utilization in analytical procedures.

Substrate or Filter Analytical procedure

All Greased PC w/ Al, PC, Teflon® (PTFE), and MCE Gravimetric Analysis

PC substrate MOUDI stage 7 (0.562–0.316 µm) and MCE

Particle Induced X-ray Emission (PIXE) Elemental composition of particulate matter

MCE MDH Method 852 (Indirect) (MDH, 1976) Transmission Electron Microscope (TEM)

Analysis for mineral fibers in air

PC substrates MOUDI stage 5 (1.780–1.000 µm) and stages 6 through 10 (1.000–0.056 µm)

ISO Method 13794 (Indirect) (ISO, 1999) TEM determination of asbestos fibers in

ambient air

MCE / copper grids from MDH852 Scanning Electron Microsope (SEM) - Mineral identification and photomicroscopy

Where:

PC = polycarbonate substrate Al = aluminum foil substrate (backing) PTFE = Polytetrafluoroethylene substrate MCE = Mixed Cellulose Ester filter

Sampling Protocol Locations for samples at ore processing sites within the taconite processing plants were selected where compositional, mineralogical, or particle size changes occur. Four locations in each processing plant were sampled during this study: 1) (fine or secondary) crusher; 2) concentrator/magnetic separators; 3) agglomerator/balling drums; and 4) kiln/pellet discharge. Identical sampling protocols were utilized at each sampling site in the processing plants. In plants that received multiple sampling events, the same exact location was sampled in each of the four process locations each time. The MOUDI and vacuum pump tote (~4 sq. ft. of floor space – Photo 3) were centrally located at each site and set up in a location that did not obstruct plant traffic adjacent to a standard power outlet. In areas where substantial plant traffic existed or could exist, the sampling equipment was flagged and taped off (Photo 4). This procedure also helped to identify the site and minimized the chance of disruption of the equipment by mine personnel during sampling. Further details regarding taconite processing plant sampling can be found in Monson Geerts et al. (2019a).


Photo 3. MOUDI sampler, TFS, and pump setup inside taconite processing facility.

Photo 4. Flagged-off sample site in potentially high-traffic corridor.

MOUDI Sampler

TFS

Pump


The MOUDI and TFS air supply was connected to either a single vacuum pump (split) or separate vacuum pumps using (1 cm inside diameter) braided conductive silicon tubing. Vacuum flow pressure for the MOUDI was adjusted to 30 L/min using the Swagelok valve off the pump and 8 L/min for the TFS sampler by appropriately adjusting a rotameter valve. Flow pressures were measured and checked using the TSI 4043 Mass Flowmeter at both the beginning and end of sampling. Care was taken to run and warm the pump(s) prior to measuring the initial flow to minimized flow variance. The average standard error in flow rates was 0.45 S.D. for the MOUDI and 0.18 S.D. for the TFS samplers. A portable handcart was used to move the vacuum pump totes between sites within each plant. In most cases, three samples were taken at each plant sampling location: 1) one two-hour size-fractionated sample using the MOUDI (see below); 2) a two-hour TFS sample that was taken simultaneously with the two-hour MOUDI sample; and 3) a second 15-minute size-fractionated sample using the same MOUDI in which the two-hour sample was collected (see below). A TFS sample was not collected during the 15-minute sample. Field blanks for each of the four types of substrates utilized during sampling were collected during the two-hour sample only. Table 4 lists the MOUDI stages and size ranges based on aerodynamic diameter and log mean diameter for the 15-minute samples. The two-hour sample time was determined to be the optimal period to collect enough PM for gravimetric analysis. This two-hour sampling period is much less than the ‘rooftop’ community sample times (120–168 hours) due to the higher concentrations of dust in the plants. This run-time was also convenient in that it enabled a total of eight samples to be collected within a one-day shift without personnel or equipment changes. The 15-minute sample consisted of a partial-stage MOUDI (only the top six stages – Table 4) and was included to create samples with a mono-layer of PM that could easily be analyzed using a scanning electron microscope (SEM). It was possible to obtain a mono-layer since the impaction plate is continuously rotating below stationary nozzles. Sample times of longer duration had the potential to create a multi-layer sample of PM on the impaction plate that would make accurate SEM analysis less reliable and more difficult. Because the NRRI only has three MOUDI samplers, it was necessary during each plant sampling event to change out sampling substrates and a TFS filter in one of the MOUDI and one of the TFS samplers. Taconite processing plant personnel arranged access to a clean room (lunchroom, dry-storage, etc.), removed from the processing plant operations, where MOUDI substrates and TFS sampler filters could be changed out by NRRI personnel. Additional set(s) of impaction plates (typically one full MOUDI set and four partial-stage sets) and TFS filter were prepared prior to the sampling event in the NRRI particle laboratory. Normally, the 15-minute sample was collected first at a particular process location, followed by the two-hour sample using the same MOUDI in that location.

Samples changed out from the first run were transferred to airtight aluminum sample holder tripods (Photo 5) and stored in a locked NRRI vehicle away from the influences of taconite processes. The TFS samplers/with filter samples were sealed and also stored in the locked NRRI vehicle. Substrate change-outs were completed efficiently with two persons and involved exposure times to the ambient air of no more than five seconds. Analysis and review of the sample series blanks from sample series that were changed on site show no significant additions of PM when compared with other sample series that were not changed out (Monson Geerts et al., 2019a).


Photo 5. Sample holder tripod.

With the exception of the aluminum housing and Davis weather station, sampling equipment used within the taconite processing facilities is identical to sampling equipment utilized for community sampling. Unlike the community sampling that required a housing to protect the instrumentation from the atmospheric elements, all plant sampling was done indoors. Because temperature and humidity conditions within similar process locations were largely similar from plant to plant, use of a weather station within the plants was deemed unnecessary. It should also be noted that, in an effort to maintain consistency in the study’s sampling protocol, aluminum housings for the MOUDI samplers were used during the first plant sampling event. However, it quickly became apparent that continued use of the housings within the plants would be problematic due to their cumbersome nature. They created safety issues and required extra effort and personnel to move from location to location within the plants. Combined with the lack of need for the atmospheric protection afforded by the aluminum housing and practical limitations for completing sampling in a timely and safe manner, use of the aluminum housings was discontinued for subsequent plant sampling campaigns. Gravimetric Analysis

Once samples were collected and returned to the NRRI, substrates were conditioned with the same pre-sampling methods, with the exception of the oven-baking technique used to remove volatiles. Gravimetric analysis was performed in a dedicated aerosol particle laboratory at the NRRI (NRRI Room 477) within 24–48 hours of collection. All scales, balances, and biosafety cabinets were certified and calibrated annually. A Cahn 25 Automatic Electrobalance was used to weigh all substrates in micrograms (µg). All filters were non-consecutively weighed twice. If the weight difference was > 0.010 µg, the substrate was re-weighed two more times. Before, during, and after the weighing process, tare weights were also weighed and recorded to keep record of any balance drift. Field blanks for each substrate type, as well as laboratory blanks, were also weighed. The field blanks were exposed to the environment


during the collection period and underwent the same conditioning/transportation as the collection substrates.

Following gravimetric analysis, the filter substrates were stored in their labeled dedicated plastic petri dishes in the original boxes in a clean, dry storage cabinet in the laboratory. They were stored there until they were needed for chemical and mineralogical analysis.

For extended detail on pre-sampling, sampling techniques, and post-sampling procedures, see Monson Geerts et al. (2019a, specifically Appendix A). Safety

All University of Minnesota personnel and consultants were MSHA certified and strictly followed company safety procedures. UM personnel and consultants also employed proper safety equipment (i.e., safety glasses, steel-toed boots with metatarsal guards, ear protection, and hardhats). Access to all site locations, sampling areas, and related travel on company property was arranged through, and accompanied by, appropriate mine safety personnel. DATA REPORTING PROTOCOLS

The gravimetric data that represents the aerosol PM sampling at all six taconite processing plants is listed in Tables 8–13. All the data is flow-weighted (concentration) with respect to the volume of air that was sampled during collection. Concentrations can then be compared for measurements from the same location as well as measurements between other locations. All gravimetric measurements that are part of this study are reported in weight/volume air (µg/m3) and/or as a mass (weight) percent (%) determined by size-fractionated data from the MOUDI II cascade impactors. (NOTE: The terms weight and mass are used interchangeably.) Tables are organized by plant, process location, plant activity, and sample series. Sample series from the tables include the measured PM concentrations and percentage of the total from each of the 10 MOUDI stages in addition to the upper greased stage (30–18 µg/m3) and the after filter (≤ 0.056 µg/m3). Also included for each sample series is specific PM breakdown (in bold), including: PM1, PM2.5, and PM10. The specific PM fractions represent important PM designations defined as: PM10 – coarse respirable particles that have aerodynamic diameters of 10 µm or less that

can settle in the bronchi and lungs and cause health problems. PM2.5 – fine respirable particles that have aerodynamic diameters of 2.5 µm or less that can

settle in the gas exchange regions of the lungs (alveoli) and cause even more serious health problems.

PM1 – the point of aerodynamic diameter which divides the coarse and accumulation modes of particles and particles resulting from comminution versus combustion, respectively.

When viewing the individual sample data, it is important to note that the reported concentrations

represent a one-time “grab sample,” or a “snapshot” of the aerosol PM levels at that particular time and place, and will exhibit some variation from sampling event to sampling event. It is also important to note that concentrations reported in the following tables do not represent regulatory monitoring, nor are they to be used for personal exposure determinations.

Compilation of the sample collection data from all six taconite plants resulted in 14 individual plant sampling events. Each sampling event consists of a total of four two-hour samples (one collected at each of the four process areas) and four 15-minute-duration samples at the same location. A total of 56 samples (two-hour) were collected within the plants, including: 12 from three plants that were inactive and 44 from active plants. Sampling of the five plants on the western MIR totaled 8 inactive samples and 32 active samples versus the one plant on the eastern MIR that had 4 inactive samples and 12 active samples.


The gravimetric data in this report are organized by the process location within the plant where the samples were collected, as this reflects particle size changes associated with ore concentration and taconite pellet production. The relationships between plant activity (active or inactive) and comparisons between results obtained at different plants are discussed in the following sections. Data pertaining specifically to PM2.5 fractions will be discussed separately below for both inactive and active plant sampling.


Table 8. Plant D: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%).

Fine Crusher Concentrator - Magnetic Separator

Series 1381 Series 1681 Series 1391 Series 1691 12-10-09 5-4-10 12-10-09 5-4-10 Inactive Active Inactive Active

MOUDI Stage #

MOUDI Stage Range (µm)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 3.15 10.56 20.72 7.44 10.20 26.64 33.94 8.69 1 18 to 10 4.26 14.29 17.45 6.27 5.45 14.23 38.62 9.89 2 10 to 5.62 3.89 13.04 27.67 9.94 3.49 9.12 30.37 7.78

3 5.62 to 3.16 2.78 9.32 30.65 11.00 3.77 9.85 34.49 8.83 4 3.16 to 1.78 1.30 4.35 30.65 11.01 2.65 6.93 36.97 9.47 5 1.78 to 1 2.04 6.83 30.36 10.91 2.65 6.93 41.36 10.59 6 1 to 0.562 -0.37 -1.24 25.68 9.23 1.26 3.28 56.21 14.41 7 0.562 to 0.316 -0.74 -2.48 18.73 6.73 0.00 0.00 37.10 9.50 8 0.316 to 0.178 -1.85 -6.21 27.24 9.79 -1.82 -4.74 28.03 7.18 9 0.178 to 0.1 -0.93 -3.11 16.18 5.81 -0.56 -1.46 18.00 4.61

10 0.1 to 0.056 1.30 4.35 13.76 4.94 0.28 0.73 14.98 3.84 F Less than 0.056 15.00 50.31 19.30 6.93 10.90 28.47 20.34 5.21 PM1 12.41 41.61 120.89 43.42 10.06 26.28 174.66 44.74 PM2.5 15.21 51.02 169.39 60.85 14.29 37.32 237.90 60.94 PM10 22.41 75.16 240.22 86.29 22.64 59.12 317.85 81.41 TOTAL 29.82 100.00 278.39 100.00 38.29 100.00 390.41 100.00


Table 8 (continued).

Agglomerator - Balling Drums Kiln - Pellet Discharge


MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 13.76 18.01 1,129.40 44.77 70.06 36.29 7,183.43 58.64 1 18 to 10 13.20 17.28 627.17 24.86 39.53 20.47 2,091.54 17.07 2 10 to 5.62 11.79 15.44 217.43 8.62 15.04 7.79 1,296.21 10.58 3 5.62 to 3.16 6.32 8.27 154.96 6.14 8.11 4.20 494.52 4.04 4 3.16 to 1.78 2.95 3.86 117.75 4.67 4.72 2.44 578.06 4.72 5 1.78 to 1 -0.14 -0.18 63.29 2.51 4.87 2.52 340.01 2.78 6 1 to 0.562 3.93 5.15 59.35 2.35 10.91 5.65 139.02 1.13 7 0.562 to 0.316 2.25 2.94 35.72 1.42 11.95 6.19 38.53 0.31 8 0.316 to 0.178 3.23 4.23 35.04 1.39 5.46 2.83 27.80 0.23 9 0.178 to 0.1 2.95 3.86 25.12 1.00 6.05 3.13 17.34 0.14

10 0.1 to 0.056 2.11 2.76 25.26 1.00 5.31 2.75 12.71 0.10 F Less than 0.056 14.04 18.38 32.05 1.27 11.06 5.73 31.25 0.26 PM1 28.50 37.32 212.54 8.43 50.74 26.28 266.65 2.18 PM2.5 30.11 39.42 345.52 13.70 58.40 30.25 948.76 7.74 PM10 49.42 64.71 765.97 30.37 83.48 43.24 2,975.45 24.29

TOTAL 76.38 100.00 2,522.54 100.00 193.07 100.00 12,250.42 100.00


Table 9. Plant B: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%).



MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 32.98 11.74 46.42 13.19 20.08 6.04 388.28 47.16 1 18 to 10 36.71 13.07 39.85 11.33 18.06 5.43 98.56 11.97 2 10 to 5.62 27.24 9.70 39.30 11.17 18.06 5.43 33.80 4.11 3 5.62 to 3.16 19.36 6.89 35.46 10.08 21.23 6.39 31.09 3.78 4 3.16 to 1.78 20.22 7.20 31.36 8.91 22.25 6.70 26.36 3.20 5 1.78 to 1 14.77 5.26 29.85 8.49 18.78 5.65 35.15 4.27 6 1 to 0.562 17.64 6.28 27.11 7.71 16.47 4.96 53.40 6.49 7 0.562 to 0.316 18.35 6.53 24.37 6.93 41.46 12.48 47.99 5.83 8 0.316 to 0.178 33.26 11.84 20.40 5.80 44.64 13.43 28.80 3.50 9 0.178 to 0.1 37.71 13.43 18.21 5.18 22.68 6.83 22.71 2.76






MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 52.43 14.88 4,173.84 70.01 32.56 16.45 1,162.62 33.79 1 18 to 10 56.96 16.16 1,087.25 18.24 31.18 15.75 1,129.57 32.82 2 10 to 5.62 44.49 12.63 242.50 4.07 21.02 10.62 285.50 8.29 3 5.62 to 3.16 33.72 9.57 136.12 2.28 14.83 7.49 309.62 9.00 4 3.16 to 1.78 29.47 8.36 91.50 1.53 8.87 4.48 215.20 6.25 5 1.78 to 1 23.52 6.67 54.98 0.92 16.21 8.19 117.29 3.41 6 1 to 0.562 20.97 5.95 41.17 0.69 11.36 5.74 75.73 2.20 7 0.562 to 0.316 18.42 5.23 30.68 0.51 10.81 5.46 30.68 0.89 8 0.316 to 0.178 18.00 5.11 25.63 0.43 8.45 4.27 26.92 0.78 9 0.178 to 0.1 17.43 4.95 21.38 0.36 13.30 6.72 26.22 0.76

10 0.1 to 0.056 20.12 5.71 21.78 0.37 10.25 5.18 23.43 0.68 F Less than 0.056 16.86 4.78 35.19 0.59 19.12 9.66 39.05 1.13 PM1 111.80 31.72 175.83 2.95 73.30 37.03 222.03 6.45 PM2.5 152.77 43.35 284.96 4.78 94.76 47.87 466.68 13.56 PM10 243.01 68.96 700.93 11.76 134.22 67.80 1,149.64 33.40 TOTAL 352.41 100.00 5,962.02 100.00 197.96 100.00 3,441.83 100.00


Table 10. Plant E: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%).


Series 1861 Series 1871 5-25-10 5-25-10 Active Active

MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 159.07 18.64 114.98 20.72 1 18 to 10 141.11 16.54 100.01 18.01 2 10 to 5.62 68.98 8.08 55.50 9.99 3 5.62 to 3.16 88.31 10.35 43.18 7.77 4 3.16 to 1.78 77.20 9.05 41.06 7.39 5 1.78 to 1 72.82 8.53 35.90 6.46 6 1 to 0.562 62.26 7.30 31.79 5.72 7 0.562 to 0.316 41.00 4.81 24.90 4.48 8 0.316 to 0.178 39.22 4.60 28.74 5.18 9 0.178 to 0.1 32.77 3.84 27.55 4.96

10 0.1 to 0.056 30.44 3.57 26.23 4.72 F Less than 0.056 40.04 4.69 25.57 4.60 PM1 245.73 28.80 164.78 29.67 PM2.5 364.24 42.69 224.98 40.51 PM10 553.04 64.82 340.42 61.29 TOTAL 853.22 100.00 555.41 100.00




Series 1881 Series 1891 5-25-10 5-25-10 Active Active

MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 1,923.04 54.75 14,441.84 68.84 1 18 to 10 742.63 21.14 4,629.95 22.07 2 10 to 5.62 299.68 8.53 651.53 3.11 3 5.62 to 3.16 188.20 5.36 477.27 2.27 4 3.16 to 1.78 107.27 3.05 248.57 1.18 5 1.78 to 1 68.84 1.96 177.28 0.84 6 1 to 0.562 48.20 1.37 96.52 0.46 7 0.562 to 0.316 28.52 0.81 50.46 0.24 8 0.316 to 0.178 31.50 0.90 46.75 0.22 9 0.178 to 0.1 25.12 0.72 37.29 0.18

10 0.1 to 0.056 23.49 0.67 33.45 0.16 F Less than 0.056 25.94 0.74 89.26 0.43 PM1 182.77 5.20 353.73 1.69 PM2.5 315.09 8.97 678.12 3.23 PM10 846.76 24.11 1,908.38 9.10

TOTAL 3,512.43 100.00 20,980.17 100.00


Table 11. Plant C: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%).


Series 611 Series 2021 Series 581 Series 2031 3-27-09 6-22-10 3-27-09 6-22-10 Active Active Active Active

MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent






Series 591 Series 2041 Series 601 Series 2051 3-26-09 6-22-10 3-27-09 6-22-10 Active Active Active Active

MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent


10 0.1 to 0.056 21.03 1.25 20.88 1.62 23.59 5.30 22.60 4.84 F Less than 0.056 13.72 0.82 25.35 1.97 8.88 1.99 28.60 6.12 PM1 120.01 7.14 149.27 11.60 157.79 35.42 144.29 30.88 PM2.5 239.44 14.24 239.66 18.62 197.18 44.26 188.76 40.40 PM10 954.75 56.80 537.35 41.75 327.32 73.47 288.95 61.84 TOTAL 1,680.90 100.00 1,287.18 100.00 445.53 100.00 467.22 100.00


Table 12. Plant F: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%).

Fine Crusher

Series 1421 Series 1581 Series 1941 3-2-10 4-8-10 6-8-10 Active Active Active

MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

0 ≈30 to 18 263.38 18.81 445.46 28.37 81.68 15.67 1 18 to 10 194.04 13.86 376.61 23.98 65.85 12.64 2 10 to 5.62 180.06 12.86 202.74 12.91 54.14 10.39 3 5.62 to 3.16 187.12 13.36 190.77 12.14 38.31 7.35 4 3.16 to 1.78 124.98 8.92 132.48 8.43 34.83 6.68 5 1.78 to 1 94.25 6.73 85.60 5.45 34.83 6.68 6 1 to 0.562 78.34 5.59 44.21 2.81 37.36 7.17 7 0.562 to 0.316 71.97 5.14 30.97 1.97 32.93 6.32 8 0.316 to 0.178 62.14 4.44 23.65 1.51 30.39 5.83 9 0.178 to 0.1 55.08 3.93 12.25 0.78 27.86 5.35

10 0.1 to 0.056 46.50 3.32 6.34 0.40 36.73 7.05 F Less than 0.056 42.63 3.04 19.71 1.25 46.22 8.87 PM1 356.66 25.47 137.13 8.73 211.49 40.58 PM2.5 524.88 37.48 301.13 19.17 266.93 51.22 PM10 943.07 67.34 748.72 47.67 373.60 71.69 TOTAL 1,400.49 100.00 1,570.79 100.00 521.13 100.00



Concentrator - Magnetic Separator


MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 161.25 23.26 137.89 28.79 241.01 38.21 1 18 to 10 93.20 13.44 115.22 24.06 88.45 14.02 2 10 to 5.62 54.94 7.92 38.50 8.04 53.18 8.43 3 5.62 to 3.16 51.87 7.48 38.77 8.10 44.84 7.11 4 3.16 to 1.78 51.41 7.41 53.38 11.15 36.50 5.79 5 1.78 to 1 52.51 7.57 28.53 5.96 33.22 5.27 6 1 to 0.562 44.26 6.38 18.57 3.88 29.94 4.75 7 0.562 to 0.316 33.95 4.89 9.28 1.94 21.33 3.38 8 0.316 to 0.178 34.92 5.03 8.74 1.82 22.28 3.53 9 0.178 to 0.1 29.83 4.30 5.73 1.20 16.68 2.64

10 0.1 to 0.056 28.46 4.10 1.73 0.36 16.81 2.67 F Less than 0.056 57.05 8.22 22.53 4.70 26.52 4.20 PM1 228.47 32.94 66.58 13.90 133.56 21.17 PM2.5 311.41 44.89 126.70 26.46 188.38 29.87 PM10 439.20 63.32 225.76 47.14 301.30 47.77

TOTAL 693.65 100.00 478.87 100.00 630.76 100.00



Agglomerator - Balling Drums


MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 3,027.88 69.24 747.61 37.88 1,534.10 47.50 1 18 to 10 349.63 8.00 395.61 20.04 499.45 15.46 2 10 to 5.62 233.79 5.35 162.79 8.24 370.98 11.48 3 5.62 to 3.16 183.02 4.19 124.53 6.31 360.07 11.14 4 3.16 to 1.78 148.10 3.39 142.83 7.23 118.25 3.66 5 1.78 to 1 122.85 2.81 100.73 5.10 85.24 2.64 6 1 to 0.562 74.61 1.71 78.99 4.00 78.01 2.41 7 0.562 to 0.316 53.15 1.22 44.31 2.24 46.24 1.43 8 0.316 to 0.178 50.07 1.15 102.10 5.17 46.37 1.44 9 0.178 to 0.1 47.96 1.10 29.45 1.49 28.51 0.88

10 0.1 to 0.056 33.52 0.77 13.49 0.68 22.78 0.70 F Less than 0.056 46.70 1.07 32.06 1.62 40.78 1.26 PM1 306.01 7.00 300.40 15.21 262.69 8.13 PM2.5 516.51 11.82 485.66 24.60 417.91 12.94 PM10 993.77 22.73 831.28 42.10 1,197.23 37.06 TOTAL 4,371.28 100.00 1,974.50 100.00 3,230.78 100.00



Kiln - Pellet Discharge


MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 4,752.59 58.92 435.29 28.03 301.23 26.32 1 18 to 10 1,574.47 19.51 492.77 31.72 363.65 31.77 2 10 to 5.62 642.61 7.96 169.38 10.91 132.65 11.59 3 5.62 to 3.16 376.07 4.66 144.59 9.31 83.95 7.34 4 3.16 to 1.78 277.55 3.44 109.83 7.07 79.42 6.94 5 1.78 to 1 157.69 1.95 69.99 4.51 53.91 4.71 6 1 to 0.562 79.67 0.99 45.01 2.90 36.35 3.18 7 0.562 to 0.316 66.33 0.82 16.20 1.04 19.20 1.68 8 0.316 to 0.178 36.19 0.45 17.87 1.15 17.15 1.50 9 0.178 to 0.1 23.53 0.29 14.27 0.92 14.81 1.29

10 0.1 to 0.056 21.88 0.27 15.65 1.01 14.27 1.25 F Less than 0.056 59.86 0.74 22.16 1.43 27.85 2.43 PM1 287.46 3.56 131.16 8.45 129.63 11.33 PM2.5 609.41 7.55 266.15 17.14 230.54 20.14 PM10 1,741.38 21.58 624.95 40.24 479.56 41.90

TOTAL 8,068.44 100.00 1,553.01 100.00 1,144.44 100.00


Table 13. Plant A: Two-hour MOUDI samples converted to concentrations - Weight/Volume Air (µg/m3) and Mass Percent (%).

Fine Crusher

Series 861 Series 1141 Series 1501 Series 1771 7-11-09 8-20-09 3-16-10 5-11-10 Inactive Active Active Active

MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent


10 0.1 to 0.056 14.41 7.31 11.83 2.04 27.77 6.32 36.15 2.60 F Less than 0.056 19.98 10.14 7.80 1.34 18.33 4.17 36.30 2.61 PM1 90.74 46.04 82.83 14.27 174.97 39.84 322.21 23.20 PM2.5 110.02 55.83 170.23 29.33 243.52 55.45 577.31 41.57 PM10 145.10 73.63 390.49 67.28 352.86 80.34 1,008.33 72.61 TOTAL 197.08 100.00 580.38 100.00 439.19 100.00 1,388.70 100.00



Concentrator - Magnetic Separator


MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent





Agglomerator - Balling Drums


MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 46.50 43.20 2,526.64 54.40 8,603.91 70.92 9,145.89 54.82 1 18 to 10 12.99 12.07 1,111.51 23.94 1,497.71 12.35 2,904.13 17.41 2 10 to 5.62 8.89 8.26 631.41 13.60 810.26 6.68 2,112.63 12.66 3 5.62 to 3.16 8.07 7.50 111.51 2.40 528.34 4.36 1,430.95 8.58 4 3.16 to 1.78 8.21 7.62 56.91 1.23 214.98 1.77 358.57 2.15 5 1.78 to 1 4.65 4.32 0.00 0.00 101.48 0.84 104.84 0.63 6 1 to 0.562 3.28 3.05 31.09 0.67 65.32 0.54 98.33 0.59 7 0.562 to 0.316 3.01 2.80 21.71 0.47 96.36 0.79 138.91 0.83 8 0.316 to 0.178 6.29 5.84 67.60 1.46 84.75 0.70 258.71 1.55 9 0.178 to 0.1 4.51 4.19 40.95 0.88 43.59 0.36 62.18 0.37

10 0.1 to 0.056 4.38 4.07 22.70 0.49 31.04 0.26 33.38 0.20 F Less than 0.056 -3.15 -2.92 21.55 0.46 51.69 0.43 35.73 0.21 PM1 18.32 17.03 205.60 4.43 372.75 3.07 627.24 3.76 PM2.5 27.83 25.86 239.28 5.15 601.46 4.96 944.29 5.66 PM10 48.14 44.73 1,005.43 21.65 2,027.81 16.72 4,634.23 27.78 TOTAL 107.62 100.00 4,643.58 100.00 12,129.43 100.00 16,684.25 100.00



Kiln - Pellet Discharge


MOUDI Stage #


Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%)

Wt./Volume Air

(µg/m3) Percent

(%) 0 ≈30 to 18 23.89 17.05 3,796.01 29.63 2,666.24 32.38 4,554.44 39.47 1 18 to 10 17.07 12.18 4,330.62 33.80 3,075.11 37.35 3,942.25 34.16 2 10 to 5.62 9.49 6.77 2,945.85 22.99 998.30 12.13 1,773.95 15.37 3 5.62 to 3.16 7.47 5.33 1,095.68 8.55 637.33 7.74 500.49 4.34 4 3.16 to 1.78 12.91 9.21 319.63 2.49 322.99 3.92 342.55 2.97 5 1.78 to 1 9.71 6.93 109.93 0.86 210.03 2.55 168.21 1.46 6 1 to 0.562 10.35 7.38 127.85 1.00 123.72 1.50 91.31 0.79 7 0.562 to 0.316 5.97 4.26 25.11 0.20 47.48 0.58 41.52 0.36 8 0.316 to 0.178 10.67 7.61 19.14 0.15 47.19 0.57 36.24 0.31 9 0.178 to 0.1 6.51 4.64 10.86 0.08 40.11 0.49 24.97 0.22

10 0.1 to 0.056 7.79 5.56 11.40 0.09 31.04 0.38 24.40 0.21 F Less than 0.056 18.35 13.09 20.81 0.16 33.59 0.41 38.66 0.34 PM1 59.62 42.54 215.17 1.68 323.13 3.92 257.10 2.23 PM2.5 76.97 54.92 514.26 4.01 724.31 8.80 628.04 5.44 PM10 99.19 70.78 4,686.26 36.57 2,491.78 30.27 3,042.30 26.37 TOTAL 140.15 100.00 12,812.89 100.00 8,233.13 100.00 11,538.99 100.00


Plant activity (inactive or active) and comminution processes are key factors in the total and PM2.5

concentrations of PM that were measured. With respect to comminution processes, the degree of fineness to which ore must be comminuted (crushed and ground) to achieve optimal magnetite recovery relative to silica content is referred to as “liberation grind.” Liberation grind is typically reported as a weight percent passing a standard mesh/sieve size (for example, 85% passing 270 mesh, i.e., < 0.053 mm). This target grind can vary from facility to facility and may contribute to some inter-plant PM variability (USEPA, 1997). However, the degree of its contribution to PM variability is unlikely to be discernible in the context of other factors such as each plant’s dust control measures and the fact that fine liberation grinding is a wet and contained process that takes place within enclosed rod and/or ball mills.

The gravimetric results, including MOUDI total, PM2.5, and percent PM2.5 from all plant sampling, are also organized by process locations and their accompanying mean values and standard deviation in Tables 14 and 15. Plants that were sampled during periods of total inactivity are summarized in Table 14. Similarly, the samples collected from active plants are summarized in Table 15. In both tables, the five western plants are grouped together and separated from the one eastern plant because of the differences in the PM due to changes in the geology, i.e., thermal metamorphism during the emplacement of the Duluth Complex intrusive rocks. The three active samples from Zone 1 and Zone 4 are compared in Table 16 and Table 17, respectively.


Table 14. Summary table of inactive sample concentrations by plant process, including both MOUDI totals and PM2.5 fraction – Weight/Volume Air (µg/m3), and PM2.5 representative percent (%) of MOUDI total.

INACTIVE INACTIVE

Crusher MOUDI Total

(µg/m3) Crusher PM2.5

Fraction (µg/m3) PM2.5

% Concentrator MOUDI Total

(µg/m3) Concentrator PM2.5


% Plant B 280.88 156.35 55.7 332.24 245.73 74.0 Plant D 29.82 15.21 51.0 38.29 14.29 37.3

Zone 1 AVERAGE 155.35 85.78 53.3 185.27 130.01 55.6 Zone 1 STD. DEV. 177.53 99.80 3.3 207.85 163.66 25.9

Plant A 197.08 110.02 55.8 204.36 102.66 50.2

OVERALL AVERAGE 113.45 62.62 53.4 121.33 58.47 43.8 OVERALL STD. DEV. 127.82 71.94 2.7 147.39 116.79 18.6

INACTIVE INACTIVE

Agglomerator MOUDI Total

(µg/m3) Agglomerator PM2.5


% Kiln MOUDI Total (µg/m3) Kiln PM2.5 Fraction (µg/m3) PM2.5

% Plant B 352.41 152.77 43.3 197.96 94.76 47.9 Plant D 76.38 30.11 39.4 193.07 58.40 30.2


Plant A 107.62 27.83 25.9 140.15 76.97 54.9



Table 15. Summary table of active sample concentrations by plant process, including both MOUDI totals and PM2.5 fraction – Weight/Volume Air (µg/m3), and PM2.5 representative percent (%) of MOUDI total.

ACTIVE ACTIVE

Crusher MOUDI Total

(µg/m3) Crusher PM2.5 Fraction

(µg/m3) PM2.5

(%) Concentrator MOUDI

Total (µg/m3) Concentrator PM2.5


(%)

Plant B 351.77 177.94 50.6 823.19 260.70 31.7

Plant C 347.04 118.09 34.0 141.01 72.09 51.1 Plant C 363.60 142.10 39.1 451.77 189.62 42.0

Plant D 278.39 169.39 60.8 390.41 237.90 60.9

Plant E 853.22 364.24 42.7 555.41 224.98 40.5

Plant F 1,400.49 524.88 37.5 693.65 311.41 44.9 Plant F 1,570.79 301.13 19.2 478.87 126.70 26.5

Plant F 521.13 266.93 51.2 630.76 188.38 29.9


Plant A 580.38 170.23 29.3 885.82 137.24 15.5 Plant A 439.19 243.52 55.4 679.90 287.96 42.4

Plant A 1,388.70 577.31 41.6 630.34 179.36 28.5

Plant A AVERAGE 802.76 330.35 42.1 732.02 201.52 28.8 Plant A STD. DEV. 512.33 216.99 13.1 135.48 77.77 13.4




ACTIVE ACTIVE

Agglomerator MOUDI

Total (µg/m3) Agglomerator PM2.5


(%) Kiln MOUDI Total

(µg/m3) Kiln PM2.5 Fraction

(µg/m3) PM2.5

(%)

Plant B 5,962.02 284.96 4.8 3,441.83 466.68 13.6

Plant C 1,680.90 239.44 14.2 445.53 197.18 44.3 Plant C 1,287.18 239.66 18.6 467.22 188.76 40.4

Plant D 2,522.54 345.52 13.7 12,250.42 948.76 7.7

Plant E 3,512.43 315.09 9.0 20,980.17 678.12 3.2

Plant F 4,371.28 516.51 11.8 8,068.44 609.41 7.6 Plant F 1,974.50 485.66 24.6 1,553.01 266.15 17.1

Plant F 3,230.78 417.91 12.9 1,144.44 230.54 20.1

Zone 1 AVERAGE 3,067.70 355.59 13.7 6,043.88 448.20 19.3 Zone 1 STD. DEV. 1,553.18 107.14 6.0 7,359.12 277.90 15.3

Plant A 4,643.58 239.28 5.2 12,812.89 514.26 4.0 Plant A 12,129.43 601.46 5.0 8,233.13 724.31 8.8

Plant A 16,684.25 944.29 5.7 11,538.99 628.04 5.4

Plant A AVERAGE 11,152.42 595.01 5.3 10,861.67 622.20 6.1 Plant A STD. DEV. 6,079.50 352.55 0.4 2,363.82 105.15 2.5

OVERALL AVERAGE 5,272.63 420.89 11.4 7,357.82 495.66 15.7 OVERALL STD. DEV. 4,831.32 213.07 6.4 6,640.14 250.75 14.2


Table 16. Summary table of active sample concentrations from Plant F by process, including both MOUDI totals and PM2.5 fraction – Weight/Volume Air (µg/m3), and PM2.5 representative percent (%) of MOUDI total.

ACTIVE ACTIVE

Crusher MOUDI Total (µg/m3)

Crusher PM2.5

Fraction (µg/m3) PM2.5 (%) Concentrator MOUDI Total (µg/m3)

Concentrator PM2.5 Fraction (µg/m3) PM2.5 (%)

Plant F 1,400.49 524.88 37.5 693.65 311.41 44.9 Plant F 1,570.79 301.13 19.2 478.87 126.70 26.5 Plant F 521.13 266.93 51.2 630.76 188.38 29.9

AVERAGE 1,164.14 364.31 36.0 601.09 208.83 33.7 STANDARD DEVIATION 563.33 140.10 16.1 110.42 94.04 9.8

ACTIVE ACTIVE

Agglomerator MOUDI Total (µg/m3)

Agglomerator PM2.5

Fraction (µg/m3) PM2.5 (%) Kiln MOUDI Total (µg/m3)

Kiln PM2.5 Fraction (µg/m3) PM2.5 (%)

Plant F 4,371.28 516.51 11.8 8,068.44 609.41 7.6 Plant F 1,974.50 485.66 24.6 1,553.01 266.15 17.1 Plant F 3,230.78 417.91 12.9 1,144.44 230.54 20.1

AVERAGE 3,192.19 473.36 16.4 3,588.63 368.70 14.9 STANDARD DEVIATION 1,198.86 50.44 7.1 3,885.00 209.22 6.6


Table 17. Summary table of active sample concentrations from Plant A by process, including both MOUDI totals and PM2.5 fraction – Weight/Volume Air (µg/m3), and PM2.5 representative percent (%) of MOUDI total.

ACTIVE ACTIVE

Crusher MOUDI Total (µg/m3)

Crusher PM2.5


(%) Concentrator MOUDI

Total (µg/m3) Concentrator PM2.5


(%)

Plant A 580.38 170.23 29.3 885.82 137.24 15.5 Plant A 439.19 243.52 55.4 679.90 287.96 42.4 Plant A 1,388.70 577.31 41.6 630.34 179.36 28.5

AVERAGE 802.76 330.35 42.1 732.02 201.52 28.8 STANDARD DEVIATION 512.33 216.99 13.1 135.48 77.77 13.4

ACTIVE ACTIVE

Agglomerator MOUDI Total (µg/m3)

Agglomerator PM2.5


(%) Kiln MOUDI Total

(µg/m3) Kiln PM2.5 Fraction

(µg/m3) PM2.5

(%)

Plant A 4,643.58 239.28 5.2 12,812.89 514.26 4.0 Plant A 12,129.43 601.46 5.0 8,233.13 724.31 8.8 Plant A 16,684.25 944.29 5.7 11,538.99 628.04 5.4

AVERAGE 11,152.42 595.01 5.3 10,861.67 622.20 6.1 STANDARD DEVIATION 6,079.50 352.55 0.4 2,363.82 105.15 2.5


RESULTS Using the flow-weighted data presented in Tables 8–13 (weight/volume air – µg/m3), the MOUDI

totals from all the sample locations can be graphed from highest to lowest and by inactive and active plants (Fig. 5). The total PM concentrations range from a high of 20,980.17 µg/m3 inside the active Plant E kiln area to a low of 29.82 µg/m3 from the inactive Plant D crusher. The same comparison can be made for the PM2.5 fraction (µg/m3), also graphed from highest to lowest and by activity (Fig. 6). Not surprisingly, the samples containing higher amounts of PM, either as a total or PM2.5 fraction, are overwhelmingly from active plants and are statistically significant (see Statistical Analysis, this report). These PM2.5 fractions range from a high of 948.76 µg/m3 inside the active Plant D kiln area to a low of 14.29 µg/m3 from the inactive Plant D concentrator area.

Graphical depictions of total PM by the MOUDI samplers and PM2.5 fractions (both averaged by plant) collected from the four plant process locations during active and inactive plant sampling events are illustrated in Figure 7 and Figure 8, respectively. Figure 7 depicts higher PM total concentrations in the active kiln and active agglomerator process areas relative to the active crusher and active concentrator process areas. The findings for these process areas were found to be statistically significant (see Statistical Analysis, this report). Inactive process areas showed no general pattern with respect to total PM concentrations.

Figure 8 illustrates PM2.5 concentrations calculated in both active and inactive plants. In summary, higher PM2.5 concentrations typically occurred in the active kiln and active agglomerator process areas relative to the active concentrator and active crusher process areas, with one exception (Plant E). Concentrations of PM2.5 in active plants were typically higher than PM2.5 concentrations in inactive plants. Inactive process areas showed no general pattern with respect to PM2.5 concentrations. More details are described in the next section on statistical analysis. Comparisons of the average total concentrations of PM and the average concentrations of PM2.5

fraction by process location and by plant activity versus inactivity are illustrated in Figure 9 and Figure 10. It is important to note that the scale in the active comparison (Fig. 10) is ten times that of the scale for the inactive comparison (Fig. 9). Also, the average concentration of all samples collected (MOUDI totals) in the five Iron Range communities is included for comparative purposes in both figures. In Figure 9 (inactive), the relative averaged concentrations of total PM in the four inactive process locations are similar, although the PM2.5 fraction makes-up greater than half of the total in the crusher and concentrator process areas. In comparison, the concentrations for PM2.5 fraction are approximately one third of the crusher/concentrator process area concentrations in the agglomerator and kiln locations. This same relationship is illustrated in active processes, with higher concentrations of coarser PM in the agglomerator and kiln process areas (Fig. 10). On average, the concentration of the PM2.5 fraction makes up approximately 15% of the average concentration of total PM in the active agglomerator and kiln process areas. Figure 11 combines the two previous figures as average representative PM2.5 fraction in percent of the MOUDI totals for inactive and active sample locations. Although an increase in the amount of PM2.5 was detected in all of the process areas during active operation, only in the areas of the agglomerator and kiln was this increase found to be statistically significant.


Figure 5. Comparison of all plant samples by plant activity: MOUDI totals as concentrations (Weight/Volume Air – µg/m3).


Figure 6. Comparison of all plant samples by plant activity: PM2.5 fractions of MOUDI totals as concentrations (Weight/Volume Air – µg/m3).


Figure 7. Comparison of concentrations by process locations (averaged by plants) – MOUDI totals (Weight/Volume Air – µg/m3).


Figure 8. Comparison of concentrations by process locations (averaged by plants) – PM2.5 fraction (Weight/Volume Air – µg/m3).


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Figure 9. Comparison of average concentrations: MOUDI totals and PM2.5 fractions – Inactive plant processes (Weight/Volume Air – µg/m3).


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Figure 10. Comparison of average concentrations: MOUDI totals and PM2.5 fractions – Active plant processes (Weight/Volume Air – µg/m3).


Statistical Analysis Statistical analyses were performed on the PM concentration data from all six plants (using JMP Pro 11, 2014; R Core Team, 2014), mostly as log10 transformed due to the non-normal distribution of the raw data. This log transformation was done for the primary reason of comparing PM concentration data based on plant activity, and between geographical locations along the BIF, especially with respect to the metamorphosed BIF in the eastern MIR. Inactive Versus Active Plants

As was explained previously, the NRRI took every opportunity to collect PM samples from inactive plants. However, only three of the six plants/mines reached full shut-down state during the course of the study. This meant that an inadequate number of samples were available to allow a robust statistical evaluation of the inactive plant data alone to be performed. However, when inactive and active plant data were both considered, a statistical evaluation was possible. Table 18 contains the results of comparisons between inactive and active operational modes at plants A, B, and D (three inactive and five active sample sets). T-tests with unequal variance were performed in JMP to determine if there was significant difference between active and inactive operation for mean and standard deviation of PM concentrations and percent at the four different process areas, where P-values greater than 0.05 indicate no significant difference. Overall, it appears that no significant difference exists between inactive and active crushers and concentrators, but active plants do appear to have significantly higher amounts of PM in both the agglomerator and kiln areas. Differences in PM between Western and Eastern MIR due to Metamorphism

T-tests were also performed on the mean and standard deviation of PM concentrations and percent detected from the four different process areas, comparing data from the five western plants with that of the one plant in the east (refer to Table 1 and Fig. 3). This comparison was performed to determine if any differences in PM occur between the BIF in the western MIR and that of the eastern MIR (McSwiggen and Morey (2008) mineral Zones 3 and 4), which has been physically and chemically changed due to contact metamorphism during the placement of intrusive rocks of the Duluth Complex. The PM data from active plant samples comparing western plants (Plants D, B, E, C, and F – combined eight sample sets total) with Plant A (three sample sets) are listed in Table 19.

Statistical T-tests with unequal variance were performed in JMP to compare if there is significant difference between these two data sets by specific process location. The results indicate that most process locations showed no significant difference (Table 19). Only the Plant A kiln had significantly greater amounts of mainly coarse PM, which may be related to housekeeping issues rather than differences in the rock. There was also a significantly higher percentage of finer PM percent (PM1 and PM2.5) in the Plant A agglomerator as well as for the PM2.5 fraction in the Plant A kiln.


Table 18. Summary of mean and standard deviation of PM percentages and log10 transformed PM concentrations for different processes at Plants A, B, and D.

A/I* Process N

% log10 transformed

PM1 PM2.5 PM10 Coarse MOUDI-T PM1 PM2.5 PM10 Coarse

Mean

A AGGLOMERATOR 5 4.53 6.85 21.65 38.22 3.83 2.45 2.63 3.14 3.40

A CONCENTRATOR 5 27.22 35.78 53.79 41.17 2.82 2.21 2.33 2.53 2.42

A CRUSHER 5 31.51 47.56 76.40 55.83 2.71 2.17 2.37 2.59 2.45

A KILN 5 3.29 7.91 30.18 58.34 3.94 2.40 2.80 3.42 3.70

I AGGLOMERATOR 3 28.69 36.21 59.46 45.95 2.15 1.59 1.70 1.92 1.81

I CONCENTRATOR 3 44.08 53.84 70.11 36.25 2.14 1.75 1.85 1.98 1.69

I CRUSHER 3 44.60 54.17 74.66 41.93 2.07 1.72 1.81 1.95 1.69

I KILN 3 35.28 44.34 60.60 41.46 2.24 1.78 1.88 2.02 1.86

Std Dev

A AGGLOMERATOR 5 2.26 3.84 7.68 11.10 0.33 0.23 0.25 0.34 0.30

A CONCENTRATOR 5 12.27 17.02 19.21 8.06 0.14 0.13 0.13 0.07 0.12

A CRUSHER 5 12.31 12.41 7.28 7.57 0.27 0.22 0.23 0.25 0.32

A KILN 5 1.96 3.67 5.01 11.74 0.24 0.07 0.12 0.22 0.24

I AGGLOMERATOR 3 10.48 9.18 12.93 6.90 0.35 0.41 0.42 0.40 0.40

I CONCENTRATOR 3 19.16 18.59 16.04 9.45 0.49 0.68 0.63 0.57 0.38

I CRUSHER 3 2.59 2.73 0.89 5.99 0.52 0.55 0.55 0.52 0.48

I KILN 3 8.27 12.71 15.11 4.64 0.08 0.08 0.11 0.10 0.11

p-value from t-test between active and inactive

AGGLOMERATOR 0.0538 0.0222 0.0212 0.2711 0.0023 0.0496 0.043 0.0135 0.0072

CONCENTRATOR 0.2629 0.2417 0.2523 0.4959 0.1335 0.3637 0.3215 0.2352 0.0724

CRUSHER 0.0752 0.3075 0.6233 0.0329 0.1578 0.2878 0.2071 0.1544 0.0899

KILN 0.0188 0.0329 0.0325 0.031 <0.0001 0.0004 0.0001 <0.0001 <0.0001 P-value less than 0.05 (shadowed in yellow) indicates a significant difference. *”A” indicates active plant; “I” indicates inactive plant.


Table 19. Summary of mean and standard deviation of PM percentages and log10 transformed PM concentrations for the western five plants compared with the eastern plant when plants are active.

Plant Process N

% log10 transformed


Mean

Plant A AGGLOMERATOR 3 3.75 5.26 22.05 39.08 3.99 2.56 2.71 3.33 3.57

Plant A CONCENTRATOR 3 21.95 28.77 48.89 43.98 2.86 2.17 2.28 2.53 2.50

Plant A CRUSHER 3 25.77 42.12 73.41 60.01 2.85 2.22 2.46 2.71 2.63

Plant A KILN 3 2.61 6.08 31.07 64.25 4.03 2.42 2.79 3.52 3.83

Others* AGGLOMERATOR 8 8.21 13.71 33.33 46.27 3.44 2.31 2.53 2.92 3.07

Others CONCENTRATOR 8 28.59 40.93 61.61 47.00 2.67 2.11 2.27 2.45 2.33

Others CRUSHER 8 29.57 41.89 67.70 52.72 2.76 2.19 2.36 2.59 2.48

Others KILN 8 12.49 19.25 38.23 49.05 3.43 2.30 2.58 2.94 3.10

Std Dev

Plant A AGGLOMERATOR 3 0.68 0.36 5.54 12.09 0.29 0.24 0.30 0.33 0.24

Plant A CONCENTRATOR 3 10.24 13.43 15.38 2.77 0.08 0.16 0.16 0.10 0.08

Plant A CRUSHER 3 12.98 13.07 6.57 6.98 0.26 0.30 0.27 0.25 0.29

Plant A KILN 3 1.17 2.46 5.15 6.24 0.10 0.09 0.07 0.14 0.12

Others AGGLOMERATOR 8 3.78 5.97 14.06 17.95 0.22 0.15 0.13 0.11 0.10

Others CONCENTRATOR 8 9.03 11.58 16.51 11.67 0.24 0.26 0.20 0.17 0.16

Others CRUSHER 8 11.13 12.69 11.52 9.55 0.29 0.21 0.22 0.25 0.33

Others KILN 8 13.21 15.29 21.25 12.67 0.64 0.17 0.27 0.38 0.56

p-value from t-test between Northshore and other five plants

AGGLOMERATOR 0.0125 0.0051 0.0895 0.4768 0.0592 0.2051 0.4205 0.165 0.0646

CONCENTRATOR 0.3905 0.2543 0.2989 0.5125 0.0788 0.6704 0.9072 0.3209 0.0471

CRUSHER 0.6823 0.9806 0.3402 0.2231 0.6502 0.8778 0.6143 0.4936 0.5048

KILN 0.0729 0.0467 0.3996 0.0305 0.0332 0.166 0.0752 0.0051 0.0075 P-value less than 0.05 (shadowed in yellow) indicates a significant difference. *Others = the other five western plants combined (Plants B, C, D, E, and F).


Zone 1 vs Zone 4 The same comparisons were calculated between Plant F and Plant A (three samples each). The

analysis yielded similar results, indicating there is no significant difference in the PM concentrations between these two plants. Table 20 contains the results of comparisons between these two plants. Plant Process Areas Ranked by PM

Using all 14 sample sets (3 inactive and 11 active), the mean and standard deviation of each process area were compared using Tukey’s ranking test (Tukey, 1949) in an attempt to statistically rank the processes by the concentration of PM. Table 21 displays the results of the tests. The PM from different process areas were ranked from largest to smallest using letters (A to C) beside the mean concentration. Cells with the same letter under the same column indicate no significant difference. The results indicate that when the plants are inactive, no significant difference in the PM concentration was found among process areas. However, this may be the result of the limited sample population size (three samples).

When plants are active (11 samples), the kiln and agglomerator process areas have significantly greater amounts of PM (including MOUDI total) than the crusher and concentrator areas, especially particles greater than 1.0 µm. The percent fraction of PM1, PM2.5, and PM10 were all significantly less in the areas of the agglomerator and kiln when compared with the crusher and concentrator areas. Concentrations of PM2.5 are ranked from largest to smallest: 1) kiln; 2) agglomerator; 3) crusher; and 4) concentrator. The coarser PM is significantly greater in the kiln and agglomerator than the crusher and concentrator (Table 21). FINE (SECONDARY) CRUSHER

Although the crushing equipment may vary slightly from plant to plant, the degree and size to which the material is typically crushed in the fine or secondary crusher is typically based on 100% passing a 1.0-inch screen. Further milling of this ore material (liberation) is generally completed by wet grinding in rod and ball mills in a process location between the secondary crusher and the concentrator. The liberation size can vary between plants and is dependent on numerous variables including, but not limited to: the stratigraphic horizon being mined, hardness of the ore, ore textures, distance from the metamorphic contact with the Duluth Complex, and the comminution required to obtain optimal magnetic Fe recovery rates. Liberation grind is typically reported as a weight percent passing a standard mesh/sieve size (for example: 85% passing 270 mesh, i.e., < 0.053 mm).

During the course of this study, the sample location for the fine (secondary) crusher within each of the six processing facilities was kept consistent. It was located in a central location (horizontally and vertically) within the fine crusher process area that was believed to best represent the PM generated by the comminution of ore.


Table 20. Summary of mean and standard deviation of PM percentages and log10 transformed PM concentrations comparing Plants A and F when plants are active.

Plant Process N % log10 transformed


Mean

Plant F AGGLOMERATOR 3 10.12 16.45 33.96 38.35 3.48 2.46 2.67 3.00 3.05 Plant F CONCENTRATOR 3 22.67 33.74 52.74 47.25 2.77 2.10 2.29 2.49 2.44 Plant F CRUSHER 3 24.93 35.96 62.23 54.13 3.02 2.34 2.54 2.81 2.75 Plant F KILN 3 7.78 14.95 34.58 54.47 3.39 2.23 2.52 2.91 3.11 Plant A AGGLOMERATOR 3 3.75 5.26 22.05 39.08 3.99 2.56 2.71 3.33 3.57 Plant A CONCENTRATOR 3 21.95 28.77 48.89 43.98 2.86 2.17 2.28 2.53 2.50 Plant A CRUSHER 3 25.77 42.12 73.41 60.01 2.85 2.22 2.46 2.71 2.63 Plant A KILN 3 2.61 6.08 31.07 64.25 4.03 2.42 2.79 3.52 3.83

Std Dev

Plant F AGGLOMERATOR 3 4.45 7.08 10.05 12.72 0.17 0.04 0.05 0.08 0.10 Plant F CONCENTRATOR 3 9.60 9.81 9.16 8.86 0.08 0.27 0.20 0.14 0.04 Plant F CRUSHER 3 15.93 16.08 12.80 9.68 0.26 0.21 0.16 0.21 0.34 Plant F KILN 3 3.92 6.58 11.28 14.68 0.46 0.20 0.23 0.30 0.33 Plant A AGGLOMERATOR 3 0.68 0.36 5.54 12.09 0.29 0.24 0.30 0.33 0.24 Plant A CONCENTRATOR 3 10.24 13.43 15.38 2.77 0.08 0.16 0.16 0.10 0.08 Plant A CRUSHER 3 12.98 13.07 6.57 6.98 0.26 0.30 0.27 0.25 0.29 Plant A KILN 3 1.17 2.46 5.15 6.24 0.10 0.09 0.07 0.14 0.12

p-value from t-test between active and inactive

AGGLOMERATOR 0.1287 0.1111 0.1665 0.9457 0.0724 0.5514 0.8512 0.2266 0.0511 CONCENTRATOR 0.9334 0.6343 0.732 0.5951 0.2617 0.7481 0.9651 0.6964 0.3191

CRUSHER 0.9468 0.6348 0.2714 0.4456 0.4712 0.6135 0.6802 0.6498 0.6623

KILN 0.1411 0.1325 0.6601 0.3741 0.1289 0.2385 0.1725 0.0516 0.0492

P-value less than 0.05 (shadowed in yellow) indicates a significant difference.


Table 21. Summary of the mean and standard deviation of PM percentages and log10 transformed PM concentrations for the four process areas when plants are inactive and active. Means of each process were compared by Tukey’s ranking test. The PM from different processes were ranked from (A) largest to (C) smallest by letters besides mean concentrations. Cells with the same letter under the same column indicate no significant difference.

Process N % log10 transformed


Active

Mean

AGGLOMERATOR 11 6.99B 11.40B 30.26B 44.31A 3.59A 2.38A 2.58AB 3.03A 3.21A CONCENTRATOR 11 26.78A 37.61A 58.14A 46.18A 2.72B 2.12B 2.27C 2.47B 2.38B

CRUSHER 11 28.53A 41.95A 69.26A 54.71A 2.78B 2.20AB 2.39BC 2.62B 2.52B KILN 11 9.80B 15.66B 36.28B 53.19A 3.59A 2.33AB 2.64A 3.10A 3.30A

Std Dev

AGGLOMERATOR 11 3.80 6.37 13.13 16.31 0.34 0.20 0.19 0.26 0.27 CONCENTRATOR 11 9.36 12.74 16.54 9.95 0.22 0.23 0.18 0.15 0.16

CRUSHER 11 11.11 12.12 10.42 9.23 0.28 0.22 0.23 0.24 0.31 KILN 11 11.99 14.24 18.24 13.06 0.60 0.16 0.25 0.42 0.58

Inactive

Mean

AGGLOMERATOR 3 28.69A 36.21A 59.46A 45.95A 2.15A 1.59A 1.70A 1.92A 1.81A CONCENTRATOR 3 44.08A 53.84A 70.11A 36.25A 2.14A 1.75A 1.85A 1.98A 1.69A

CRUSHER 3 44.60A 54.17A 74.66A 41.93A 2.07A 1.72A 1.81A 1.95A 1.69A KILN 3 35.28A 44.34A 60.60A 41.46A 2.24A 1.78A 1.88A 2.02A 1.86A

Std Dev

AGGLOMERATOR 3 10.48 9.18 12.93 6.90A 0.35 0.41 0.42 0.40 0.40 CONCENTRATOR 3 19.16 18.59 16.04 9.45 0.49 0.68 0.63 0.57 0.38

CRUSHER 3 2.59 2.73 0.89 5.99 0.52 0.55 0.55 0.52 0.48 KILN 3 8.27 12.71 15.11 4.64 0.08 0.08 0.11 0.10 0.11

Rankings represented by different letters in a column (shadowed in yellow) indicate a significant difference.


Crusher Gravimetric Results Total PM MOUDI concentrations for inactive crusher samples (three total) ranged from a low of

29.82 µg/m3 at Plant D to a high of 280.88 µg/m3 at Plant B, and averaged 169.26 µg/m3 (Table 14, Fig. 7). These inactive concentrations can be compared with active samples (11 total: Table 15, Fig. 8) ranging from 278.39 µg/m3 at Plant D to 1570.79 µg/m3 at Plant F (average 735.88 µg/m3). Overall, average aerosol PM levels were approximately 3.5 times higher when the crushers were active versus inactive (Tables 14 and 15). The average active crusher PM concentrations from the two individual processing facilities that were sampled three times each (Plants A and F) were 802.76 µg/m3 and 1164.14 µg/m3, respectively (Table 15). The Plant A crusher average is similar to the overall active calculated average total PM MOUDI concentration for the crusher area of all six plants.

The PM2.5 weight fraction from samples collected in the fine crusher areas of all six plants showed a wide range of variability during both inactive and active operation (Tables 14 and 15). This weight fraction also displayed differences between separate samples (i.e., samples collected on different dates) within the same plants. The overall average concentrations of PM2.5 from inactive and active plants were 93.86 µg/m3 and 277.80 µg/m3, respectively (Tables 14 and 15). The average PM2.5 concentration from active plants was approximately three times higher than from inactive plants. Crusher – Inactive PM2.5

The overall PM2.5 average concentration of 93.86 µg/m3 was calculated from the three samples collected from inactive plants A, B, and D (Table 14). When compared between plants, these PM2.5 levels varied substantially. Plant B had the highest concentration of inactive PM2.5, measuring 156.35 µg/m3, whereas Plant D had the lowest concentration, measuring 15.21 µg/m3. It is worth noting, however, that the PM2.5 fraction of each sample is similarly consistent at 55.8%, 55.7%, and 51.0% of the MOUDI totals. On average, the percentage of each MOUDI total represented by the PM2.5 fraction in inactive plants is 54.2%, with a standard deviation of 2.7 (Table 14 and Fig. 9). The PM2.5 fraction is substantially greater on average in the inactive process areas compared to the active process areas (Tables 14 and 15) and is statistically significant in the areas of the agglomerator and kiln (Fig. 11). This relationship may be the result of the finer PM fraction taking longer to settle than coarser PM fraction, and the finer PM fraction representing a greater percentage of the total PM in inactive locations. Crusher – Active PM2.5

The PM2.5 concentrations from individual active plants varied substantially and ranged from a low of 118.09 µg/m3 at Plant C, to a high of 577.31 µg/m3 at Plant A (Table 15). The overall PM2.5 average concentration of 277.80 µg/m3 was calculated from 11 samples collected from all active plant samples. The average PM2.5 concentration from the two plants that were sampled three times was comparable at 330.35 µg/m3 from Plant A and 364.31 µg/m3 from Plant F. Plant C was sampled twice when active, with an average active PM2.5 concentration of 130.10 µg/m3 (Table 15). This average PM2.5 concentration was lower than the overall PM2.5 average concentration from all plants.


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Error Bars = Standard Deviation

Figure 11. Average representative PM2.5 fraction in percent of the MOUDI totals for inactive and active sample locations. Error bars represent one standard deviation.


In active plants (Table 15), the representative PM2.5 fractions were highly variable and ranged from 19.2% to 60.8% of the MOUDI PM totals. The average of these active PM2.5 fractions was 42.0%, with a standard deviation of 12.1. Although variation exists between the multiple samples collected in individual plants, the average percent fraction of the respective totals of these samples compared well. Plant A’s PM2.5 fraction average was 42.1% (Table 15), and Plant E’s PM2.5 fraction average was 36.0% (Table 15).

The findings of this study indicate there is a higher ratio of the fine fraction to the coarse fraction in inactive plant crusher process areas compared with active crusher process areas (54.2% versus 42.0%; Tables 14 and 15). This result is believed to reflect a higher degree of settling of the coarse PM in plants that are inactive, while the finer PM remains in suspension longer and is more prone to re-suspension. Concentrator/Magnetic Separator

In general, the mechanisms and processes located within the concentrating and magnetic separator process areas of each plant were similar, respectively. A processing scheme comprising multiple feeds into rod mills, followed by magnetic separators, was predominant. An effort was made to centrally locate the sample collection sites amongst both types of machinery in each of the six facilities. Concentrator Gravimetric Totals

The three inactive concentrator samples (total MOUDI weights) varied substantially in Total MOUDI PM concentrations and ranged from 38.29 µg/m3 at Keetac to 332.24 µg/m3 at Hibtac and averaged 191.63 µg/m3 (Table 14). Total MOUDI PM concentrations for active samples were quite variable and ranged from a low of 141.01 µg/m3 at Plant C to a high of 885.82 µg/m3 at Plant A and averaged 578.28 µg/m3 (Table 15). Overall, average aerosol PM concentrations were approximately three times higher when the concentrators were active versus inactive (Tables 14 and 15). The average active concentrator PM concentrations from Plant A and Plant F were 732.02 µg/m3 and 601.09 µg/m3, respectively; average results from Plant F’s concentrator are most representative of the overall average concentrations of all active plants. Concentrator – Inactive PM2.5

The calculated PM2.5 fraction concentrations from inactive plants were variable and ranged from a low of 14.29 µg/m3 at Keetac to a high of 245.73 µg/m3 at Hibtac (Table 14). The overall average PM2.5

fraction concentration from the three samples was 120.89 µg/m3. Representative percent fractions of PM2.5 relative to the MOUDI totals were also variable and ranged from 37.3% at Keetac to 74.0% at Hibtac (Table 14). The average from these three PM2.5 fractions in inactive plants was 53.8% of the MOUDI totals, which is comparable to the fractional percent of PM2.5 (54.2%) that was obtained in inactive crusher process areas (Table 14 and Fig. 9). The PM2.5 fraction in the concentrator was found to be greater in inactive concentrator process areas compared to the active concentrator process areas, but the difference is not statistically significant (Fig. 11). Concentrator – Active PM2.5

The active concentrator PM2.5 concentrations exhibited less variability than the active samples from the crushers (Table 15). An overall average PM2.5 concentration of 201.49 µg/m3 was calculated, ranging from a low of 72.09 µg/m3 from Plant C to a high of 311.41 µg/m3 from Plant F. Both Plant A and Plant F, which were sampled three separate times, had similar active plant average PM2.5 concentrations of 201.52 µg/m3 and 208.83 µg/m3, respectively, similar to the overall calculated average concentration for active plants.

The PM2.5 concentration from active plants was approximately twice that from inactive plants (201.49 µg/m3 versus 120.89 µg/m3, respectively; see Tables 14 and 15). When calculated as a percent of the MOUDI totals, the PM2.5 average is 37.6% (Table 15). Despite variations on a plant by plant basis,


the overall PM2.5 percentage in the active concentrators is comparable to the active crusher PM2.5 (37.6% versus 42.0%; Table 15), just as the average percent PM2.5 from inactive crusher and concentrator process areas are similar (Fig. 9; Table 14). Agglomerator/Balling Area

Five of the taconite processing facilities utilize balling drums in the generation of taconite pellets, while the sixth facility incorporates balling discs. Statistical analyses did not identify any differences between PM concentrations between Plant F and Plant A (Table 20). Agglomerator Gravimetric Totals

Total MOUDI PM concentrations for inactive agglomerator samples (three total) ranged from a low of 76.38 µg/m3 at Plant D to a high of 352.41 µg/m3 at Plant B and averaged 178.80 µg/m3 (Table 14). The inactive concentrations can be compared with active agglomerator PM concentrations, ranging from 1,287.18 µg/m3 at Plant C to 16,684.25 µg/m3 at Plant A (Table 15). The average of all 11 active samples was 5,272.63 µg/m3 (Table 15). Overall, average aerosol PM concentrations were nearly 30 times higher in the agglomerator process areas when plants were active versus inactive (Tables 14 and 15). These overall averages can be compared to the average active agglomerator PM concentrations determined for the plants that were sampled multiple times (Plant A and Plant F); 11,152.42 µg/m3 and 3,192.19 µg/m3, respectively (Table 15).

Due to the relatively high concentrations of aerosol PM in agglomerator process area of the plants, the averages from the two plants that were sampled multiple times (Plants A and F) varied substantially (more than the overall active agglomerator process area calculated average). Plant A displayed substantially higher concentrations of PM in the agglomerator process area than any other plant. Although one of the three MOUDI total samples in Plant A approximated the overall average (4,643.58 µg/m3), the remaining two contained much higher levels of PM at 12,129.43 µg/m3 and 16,684.25 µg/m3, roughly two to three times higher than any other plant. Total MOUDI PM samples from Plant F varied from a low of 1,974.50 µg/m3 to a high of 4,371.28 µg/m3 and averaged 3,192.19 µg/m3, below the overall average of all active plant Total MOUDI PM (5,272.63 µg/m3). Agglomerator – Inactive PM2.5

Of the three samples comprising inactive plant agglomerator process areas, two have similar values and the third is approximately 3–5 times higher. These PM2.5 concentrations are (in ascending order) 27.83 µg/m3 from Plant A, 30.11 µg/m3 from Plant D, and 152.77 µg/m3 from Plant B. The overall average PM2.5 concentration from the three plants is 70.23 µg/m3 (Table 14). Representative fractions of the MOUDI totals ranged from 25.9% at Plant A to 43.3% at Plant B, with an average of 36.2% of the MOUDI totals and a standard deviation of 9.2% (Table 14 and Fig. 9). The PM2.5 fraction in the agglomerator process area is significantly greater for samples from the inactive process area compared to samples from the active process area (Fig. 11). Agglomerator – Active PM2.5

In active agglomerator process areas (Table 15), the PM2.5 concentrations varied somewhat from plant to plant but—with the exception of Plant A—were generally consistent between multiple samples collected from the same plant. Overall, PM2.5 concentrations ranged from a low of 239 µg/m3 (three samples total—two from Plant C and one from Plant A) to a high of 944.29 µg/m3 from Plant A, with an overall average of 420.89 µg/m3 (Table 15). Plant C and Plant F had consistent PM2.5 values within each plant. Plant C was sampled twice and had the lowest average PM2.5, with PM2.5 concentrations of 239.44 µg/m3 and 239.66 µg/m3 (Table 15). Plant F also had relatively consistent PM2.5 concentrations at 516.51 µg/m3, 485.66 µg/m3, and 417.91 µg/m3. Plant A was the only plant sampled multiple times where agglomerator process area PM2.5 concentrations varied considerably: 239.28 µg/m3,


601.46 µg/m3, and 944.29 µg/m3 (Tables 15 and 16). Plant A also had the highest average PM2.5

concentration at 595.01 µg/m3 (Table 15). The agglomerator process areas of inactive plants had a lower average PM2.5 fraction relative to

inactive crusher and concentrator areas (Table 14). Although the active plant agglomerator process areas averaged nearly six times the amount by weight of PM2.5 than the inactive plant agglomerator process areas (Tables 14 and 15), the percent fraction for the agglomerator process area PM2.5 fraction in inactive plants was much greater (averaging 36.2%) relative to agglomerator process areas in active plants that averaged 11.4% for the PM2.5 fraction. Standard deviations for these averages were 9.2% and 6.4%, respectively (Tables 15 and16). KILN/PELLET DISCHARGE

Two types of “kilns” are found within the taconite processing plants on the MIR: 1. Grate-Kiln Cooler System, which dries and preheats the pellets to 1800° F, fires the pellets in

a kiln at 2400° F, and finally cools the finished pellet product in a rotary cooler (Plants A, C, D, and E); and

2. Traveling-Grate System, which technically has no kiln, fires flux-type pellets at 2375–2425° F and acid pellets at 2400–2450° F (Plants B and F).

Both types of “kilns” dry, preheat, fire, and cool the finished pellet product to produce a taconite pellet with a pellet compression strength that is dictated by the producer and/or their customer(s). At each plant, a centrally located site at the pellet discharge-end of the “kilns” was selected and sampled. Kiln Gravimetric Totals

Three inactive kiln/pellet discharge process area samples (total MOUDI weights) were collected; concentrations ranged from 140.15 µg/m3 at Plant A to 197.96 µg/m3 at Plant B and averaged 177.06 µg/m3, with a standard deviation of 32.06 µg/m3 (Table 14). The total MOUDI concentrations for active samples collected in the pellet discharge process area of the kiln varied widely, ranging from a low of 445.53 µg/m3 at Plant C to a high of 20,980.17 µg/m3 at Plant E, and averaged 7,357.82 µg/m3. Overall, average aerosol PM concentrations were over 40 times higher when the kilns were active versus inactive (see Tables 14 and 15). For the two plants that were sampled three times, the average active kiln total PM concentrations from Plant A and Plant F were 10,861.67 µg/m3 and 3588.63 µg/m3, respectively (Table 15). Kiln – Inactive PM2.5

All three inactive kiln samples contained similar PM2.5 concentrations (Table 13). They range from a low of 58.40 µg/m3 at Plant D to a high of 94.76 µg/m3 at Plant B and average 76.71 µg/m3. Similar to samples obtained from the agglomerator process area (PM2.5 = 36.2% of average MOUDI total), the average PM2.5 concentration represented 44.3% of the average total MOUDI amount from samples obtained in the kiln process area. These PM2.5 percentages are in contrast with PM2.5 percentages obtained for samples from inactive crusher and concentrator process areas, where it was found that the PM2.5 fraction represents approximately 54% of the MOUDI total (Fig. 9). The average PM2.5 fraction in the agglomerator process area is also significantly greater in the inactive process compared to the active (Fig. 11). Kiln – Active PM2.5

The active kiln samples contained PM2.5 concentrations that were variable, ranging from a low of 188.76 µg/m3 at Plant C to a high of 948.76 µg/m3 at Plant D, with an average of 495.66 µg/m3 and a standard deviation of 250.75 µg/m3 (Table 15). At plants where three samples were collected, Plant A exhibited the most consistency between samples, with an average concentration of 622.20 µg/m3 and a


standard deviation of 105.15 µg/m3. Plant F showed more variability, with two samples having concentrations of 266.15 µg/m3 and 230.54 µg/m3 and a third sample having a concentration of 609.41 µg/m3. The average concentration at Plant F was 368.70 µg/m3, with a standard deviation of 209.22 µg/m3.

For active plants, the PM2.5 fraction of the total MOUDI PM in the active kiln process area had an overall average of 15.7%. In comparison, the average PM2.5 fraction of the total MOUDI PM collected from active agglomerator process areas was 11.4%. By contrast, the average PM2.5 fraction from active crusher process areas and active concentrator process areas is approximately 40% of the MOUDI total (Fig. 10, Table 15).

When comparing between inactive versus active plant operations, the average PM2.5 concentrations associated with the crusher and concentrator process areas have a ratio of ~1.5:1. By contrast, the agglomerator and kiln process areas were found to have an average PM2.5 concentration ratio of approximately 3:1 when comparing results from inactive and active plants. This ratio can be explained by the smaller weight percent fraction that the PM2.5 represents in both the agglomerator and kiln process areas. Plant Multiple Sample Events

Two taconite processing facilities, Plants A and F, were sampled three separate time during active operation. These facilities were chosen because of their geographical locations on the MIR and because they obtain their ores from different metamorphic zones (French, 1968; McSwiggen and Morey, 2008). While the BIF at the Plant F mine (located in Zone 1) was not significantly thermally metamorphosed by the intrusion of the Duluth Complex, the BIF mined and subsequently processed at Plant A has been affected by the intrusion’s thermal metamorphism and has been changed mineralogically, physically, texturally, and chemically (Zone 4). As with the other plant data, the MOUDI data from each of the three sampling events at each plant has been broken down by weight/volume air (µg/m3) and mass (or weight) percent for each of the processes listed in Tables 12 and 13 (Plant F and Plant A, respectively). These data are summarized by MOUDI PM totals and PM2.5 fraction by weight/volume air (µg/m3) and percent (%) PM2.5 representative of the MOUDI total (Tables 16 and 17). Plant A Summary

The results of the three active sampling events in Plant A are consistent with the data calculated from the 11 active plant sample events from the six taconite processing facilities on the MIR (Table 15 and Table 17). This similarity is supported by the relatively low standard deviations—in particular, the percent of MOUDI total PM represented by the PM2.5 fraction. Plant A samples from the active crusher processing area had a MOUDI total PM average of 802.76 µg/m3 compared with the overall active crusher processing area average of all sampled taconite plants 735.88 µg/m3. As well, the sampling events in active crusher process areas yielded a representative percent PM2.5 weight fraction of 42.1% for Plant A versus the overall PM2.5 weight fraction of 42.0% for all 11 active plant sampling events.

Active concentrator process area samples at the Northshore facility averaged 732.02 µg/m3 (Table 17). This value is slightly higher than the overall average of 578.28 µg/m3 from active concentrator process area samples from all MIR taconite plants. However, the average PM2.5 weight percent for active concentrator process area samples at Plant A was 28.8% (Table 17). This value is lower than the overall 37.6% PM2.5 weight fraction determined for active concentrator process area samples from all the plants. The PM2.5 representative fraction of the MOUDI total in both the crusher and concentrators in all plants was approximately one third of the sample (33.7%, Table 16).

Plant A had the highest MOUDI totals for samples from the active agglomerator process area (11,152.42 µg/m3 average; Table 17). This compares with the average MOUDI total PM value of 5272.63 µg/m3 obtained from active agglomerator process areas from all plants. Plant A had one of the


lowest average PM2.5 fraction percentages (5.3%) for active agglomerator process area samples from all MIR taconite plants (average 11.4%).

The samples collected from active kiln process areas in Plant A yielded a higher average MOUDI total PM of 10,861.67 µg/m3 relative to the average MOUDI total PM of 7357.82 µg/m3 for all active MIR plants (Table 17). The average percentage PM2.5 of 6.1% from active kiln process area samples in Plant A was below the overall average percentage of PM2.5 of 15.7% obtained in active kiln process areas for all MIR taconite plants. Plant F Summary

Plant F had similar results to Plant A (see Table 15–Table 17). The average MOUDI total PM for samples taken in the active crusher processing area, 1164.14 µg/m3, was the highest average MOUDI total PM obtained for active crusher processing area samples for all the plants. This average value exceeded the average MOUDI total PM of 735.88 µg/m3 for active crusher process areas in all MIR taconite processing plants. The average PM2.5 weight fractions for active crusher processing area samples at Plant F was 36.0% (Table 16), which is less than the overall average of 42.0% for active crusher processing area samples for all MIR taconite plants (Table 15).

Average active concentrator process area MOUDI total PM values were 601.09 µg/m3 at Plant F, similar to the overall average of 578.28 µg/m3 for active concentrator process area samples collected at all MIR taconite plants. The PM2.5 percent for the Plant F active concentrator process area was 33.7%, which is slightly less than the overall average PM2.5 percentage for active concentrator process areas obtained from all MRI taconite plants—37.6% (Table 15). The average PM2.5 fraction for the active concentrator process area in Plant F is similar to the average PM2.5 value obtained from the Plant F active crusher process area (36.0%).

The active agglomerator process area MOUDI total PM measurements for Plant F averaged 3192.19 µg/m3, substantially less than the overall average for active agglomerator process area samples at all MIR taconite plants of 5272.63 µg/m3 (Table 16 and Table 15, respectively). The average PM2.5

weight fraction for the the active agglomerator process area at Plant F averaged 16.4% relative to the average PM2.5 fraction for all active agglomerator process area samples of 11.4% for all MIR taconite plants.

The average active kiln process area MOUDI total PM at Plant F (3588.63 µg/m3) was approximately half of the overall average MOUDI total PM (7357.82 µg/m3) for all active plants (Table 16 and 15, respectively). The average PM2.5 fraction of 14.9% for active kiln process area samples at Plant F is similar to the average PM2.5 fraction of 15.7% obtained from active kiln process area samples for all MIR taconite plants. Particulate Matter Mass Percentages by Aerodynamic Diameter: Mode Comparison In general, the graphing of mass distribution PM mass on a lognormal scale from each of the individual stages of the MOUDI results in a unique bimodal pattern. The “coarse” mode particles make up the first mode, ranging in size from 18 µm down to 1.0 µm. This “coarse mode” fraction is composed primarily of rock and mineral particles generated by comminution. Finer particles ranging in size from 1.0 µm to less than 0.056 µm form a second “accumulation” mode, and these particles are typically composed of matter generated through chemical reactions such as combustion (Hinds, 1999). However, this bimodal pattern is not always observed, especially in very-high-PM environments. For example, this can occur in taconite processing facilities, where the “coarse” PM mode can be orders of magnitude greater than the accumulation mode. Few of the graphs from the taconite processing facility plant sample collection events illustrate a bimodal distribution (Figs. 12a-b – 19a-b). Therefore, it is more practical and representative to display the aerodynamically fractionated PM mass data from the individual MOUDI stages as a mass percent of the total PM collected. Using this method, it is easier to compare the graphs, not only on a plant-by-


plant basis, but also from each of the four specific process areas of each plant, because the data are normalized to sampling volumes.

A series of particle size distribution graphs based on PM aerodynamic diameter and mass percent were generated using the computer software DistFit™ 2009.01 (1988–2012). The first set of graphs represent an “overall plant average,” in which the separate stages of the MOUDI total PM were averaged from the 3 inactive plant samples and from all 11 active plant sampling events by each of the four areas of the plants (Fig. 12a-b, Fig. 14a-b, Fig. 16a-b, and Fig. 18a-b). Note that error bars are provided in each of the figures for each stage. These error bars represent one calculated standard deviation. Two similar series of graphs were generated from the data obtained from the two plants (Plants A and F) that were sampled three times each during active operation. Figures 12a-b – 19a-b display the side-by-side comparisons of graphs generated from all the plant data “overall” for both inactive (Plants A, B, and D) and active plants (Plants A–F), as well as from the active Plant A and Plant F operations. RESULTS Complete gravimetric results for all sampling completed at MIR taconite plants during this study have been reported in Tables 8–13 (see pages 29–44), where the data are reported both as mass per volume of air (µg/m3) as well as percent of mass on each MOUDI stage relative to the total PM mass collected during the sampling series. For ease of reference, these results have been consolidated and are summarized in Tables 22–27 for PM1, PM2.5, PM10, and Total PM for each sampling series and for each process location within Plants A through F.


Plant A Results Plant A was sampled on four occasions, including once when the plant was inactive and three times when the plant was active. Sampling results are summarized in Table 22 for all four process locations. Table 22. Plant A – PM1, PM2.5, PM10, and TOTAL PM summaries.


Plant B Results Plant B was sampled on two occasions: once when the plant was inactive and once when the plant was active. Sampling results are summarized in Table 23 for all four process locations. Table 23. Plant B – PM1, PM2.5, PM10, and TOTAL PM summaries.


Plant C Results Plant C was sampled twice when the plant was active. No inactive plant sampling occurred. Sampling results are summarized in Table 24 for all four process locations. Table 24. Plant C – PM1, PM2.5, PM10, and TOTAL PM summaries.


Plant D Results Plant D was sampled on two occasions: once when the plant was inactive and once when the plant was active. Sampling results are summarized in Table 25 for all four process locations. Table 25. Plant D – PM1, PM2.5, PM10, and TOTAL PM summaries.


Plant E Results Plant E was sampled once when the plant was active. Sampling results are summarized below in Table 26 for all four process locations. Table 26. Plant E – PM1, PM2.5, PM10, and TOTAL PM summaries.


Plant F Results Like Plant A, Plant F was sampled three times when the plant was active. No inactive plant sampling occurred. Sampling results are summarized below in Table 27 for all four process locations. Table 27. Plant F – PM1, PM2.5, PM10, and TOTAL PM summaries.


DISCUSSION – PARTICULATE MATTER MASS PERCENTAGES AND AERODYNAMIC DIAMETER In this section, we summarize the size-fractionated mass data resulting from investigations in all plants (Figs. 12 a-b, 14a-b, 16a-b, and 18a-b) as well as Plant A and Plant F, which were sampled three times while plants were actively operating (Figs. 13a-b, 15a-b, 17a-b, and 19a-b).

Observations from the plant PM sampling can be summarized as follows: In almost all cases, the average mass percent per range of PM decreases with decreasing

aerodynamic diameter for process areas in active plants. This observation generally also holds true for process areas in plants that were inactive (the exceptions being overall plant average crusher and concentrator process area results indicated in Figs. 12a and 14a).

It can be observed that the decrease in particle mass percent with decreasing aerodynamic diameter is more evident in the latter stages of the taconite process, i.e., agglomerator and kiln process areas. The comparisons between the graphs from the active crusher process areas (Figs. 12b, 13a, and 13b) and the active agglomerator process areas (Figs. 16b, 17a, 17b) and active kiln process areas (Figs. 18b, 19a, and 19b) illustrate this point well, showing a more consistent size distribution of PM in the active crusher process areas and a more skewed size distribution between fine and course PM in the active agglomerator and active kiln process areas.


Figure 12a-b. Comparison of averages from MOUDI stages of all Inactive (3 samples, Fig. 12a) and Active (11 samples, Fig. 12b) sampling within the crusher process areas.

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Figure 13a-b. Comparison of averages from MOUDI stages of Plant A and Plant F (n=3 each) from the Active crusher areas of plant sampling.

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Figure 14a-b. Comparison of averages from MOUDI stages of overall Inactive (3 samples) and Active (11 samples) concentrator areas of plant sampling.

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Figure 15a-b. Comparison of averages from MOUDI stages of Plant A and Plant F (three samples each) from the Active concentrator areas of plant sampling.

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Figure 16a-b. Comparison of averages from MOUDI stages of overall Inactive (3 samples) and Active (11 samples) agglomerator areas of plant sampling.

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Figure 17a-b. Comparison of averages from MOUDI stages of Plant A and Plant F (three samples each) from the Active agglomerator areas of plant sampling.

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Figure 18a-b. Comparison of averages from MOUDI stages of overall Inactive (3 samples) and Active (11 samples) kiln areas of plant sampling.

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Figure 19a-b. Comparison of averages from MOUDI stages of Plant A and Plant F (three samples each) from the Active kiln areas of plant sampling.

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In general, it was found that a higher percentage of the total MOUDI PM mass is represented by the PM2.5 fraction in the areas of the crusher (Figs. 12a-b and 13a-b) and concentrator (Figs. 14a-b and 15a-b) than in the areas of the agglomerator (Figs. 16a-b and 17a-b) and kiln (Figs. 18a-b and 19a-b). This is evident from sampling during both plant inactivity and plant activity. It appears that these general findings are more evident in active plants.

The overall average representative mass fraction of PM2.5 from active crushers and concentrators remained slightly above 30%. Despite a contrast in plant atmospheric conditions between the agglomerator (humid) and the kiln (hot and dry), the ratio of representative PM2.5 fraction related to the MOUDI totals for active agglomerator and kiln samples was approximately a third of that determined for active crusher and concentrator samples and remained relatively constant at approximately 10% (Table 15).

The graphs generated from averages of the three inactive plant sampling events (Figs. 12a, 14a, 16a, and 18a) show a more even distribution of PM mass among the various PM aerodynamic cut sizes (MOUDI stages) relative to that identified for active samples. The MOUDI totals (µg/m3) are substantially lower during plant inactivity than during plant activity; however, the representative mass fractions of PM2.5 for inactive plants are actually higher.

The PM2.5 mass fraction is shown in Tables 14 and 15 as well as in Figures 11–19a-b. The combined representative PM2.5 fractions from both the crushing and concentrating process areas of the inactive plants were approximately 54%, while those from the agglomerator and kiln areas were 36% and 44%, respectively (Table 14). Statistical analyses indicate that differences in PM concentrations and modal percentages between inactive and active operations are only significant within the agglomerator and kiln (see Statistical Analysis results and Table 21, this report).

Particle Size Analysis Particulate matter generated by multi-event comminution processes can also be analyzed by size distribution data and cumulative fraction weight percent. The particulate samples that were collected using MOUDI impactors in each process location of the taconite processing facilities are ideal for this analysis. Because impaction substrates on the stages within the MOUDI collect a specific size range of particle (based on aerodynamic properties), the log mean diameter of each range is used in the graphing (see Tables 3 and 4 for the corresponding log mean diameter of each MOUDI stage). Two common size distribution equations that have been used in industrial mineral engineering for a half century were reviewed. These included the Gates (1915)-Gaudin (1926)-Schuhmann (1940) and the Rosin-Rammler (1933) size distribution equations. Plotted on a log-log scale, these curve-fitting equations typically display two distinct size distribution regions comprising fine (less than 1 µm) and coarse (greater than 1 µm) particulate matter. Since the aerosol PM samples primarily consist of the ‘fine’ fraction, and the Rosin-Rammler equation is more suited for use in the coal industry, only the Gates-Gaudin-Schuhmann equation was used in this study. Graphically, the size distribution data are expressed as cumulative fractions by weight percent undersize, Y, (or oversize, Y’ = 100 – Y) in relation to size, X, which display the multi-event comminution through each of the plant’s process areas (Harris, 1968). The data from plants that were inactive and plants that were active were used to generate the corresponding particle size distribution graphs (Figs. 20 and 21). Both graphs include separate plots of both oversize and undersize cumulative weight percent. Both graphs show log normal distribution of the data with deviation at the smaller particle size fraction, which creates a somewhat deceptive final curve. Because of this, a third graph (Fig. 22) was generated with only the oversize weight percent fraction to illustrate the differences in weight percent


oversize fraction and particle size between average inactive and active locations in the plants. Linear ‘best-fit’ curve fitting was employed to construct this graph. The results of the graphs reinforce the observations from the data tables and DistFit plots above. In general, it was found that a greater weight percent fraction oversize of the inactive plants (bold lines on Fig. 22) is represented by the finer PM fractions for all process areas when compared with the weight percent fraction oversize results in all process areas in active plants. All four of the best-fit curves for inactive plants occur at the top of the particle sized distribution graph (Fig. 22). In the order of highest to lowest weight percent fraction oversize, the process area ranking was found to be crusher, concentrator, kiln, and agglomerator. This same order is observed in the active plots below. The reason for the kiln having a higher weight percent fraction oversize than that in the agglomerator (in both cases) is not fully understood. However, this difference may be related to humidity (the agglomerator is a wet process, whereas the kiln is a hot and dry process). The results may also reflect the influence of convective air currents in the relatively hotter and drier kiln area, where temperature gradients are more pronounced under active conditions. The kiln/pellet discharge areas are also located near the ends of the plants and to openings (doors, windows, fan grates) to the outdoors, which may also contribute to greater air movement, thereby keeping the smaller PM in the kiln area in suspension, even during inactive periods. The slopes for active and inactive process areas on the particle size distribution plot also reflect the nature of the PM sampled in each of these process areas. The steeper the slope of best-fit curve, a greater variability between the coarse and fine particle distribution at that process area location. Best-fit curves of the average inactive process area locations at the top of the particle sized distribution graph indicate a more consistent distribution of particle size (inactive crusher and concentrator), whereas best-fit curves with steeper slopes (active agglomerator and kiln) indicate a higher weight percent oversize relative to the fine fractions. This same result is consistent with the results indicated in the DistFit plots in Figs. 12a-b – 19a-b.


0.01 0.1 1 10Particle Size ( m)

0.01

0.1

1

10

100

Wt.

Perc

ent O

vers

ize

Y' =

100

- Y

LEGENDCrusher OversizeCrusher UndersizeConcentrator OversizeConcentrator UndersizeAgglomerator OversizeAgglomerator UndersizeKiln OversizeKiln Undersize

PARTICLE SIZE-DISTRIBUTIONInactive Taconite Processing Facilities

Wt.

Perc

ent U

nder

size

Y

Figure 20. Particle size distribution related to multi-event comminution processes from inactive plants: Wt. % oversize versus undersize.



0.01

0.1

1

10

100

Wt.

Perc

ent O

vers

ize

Y' =

100

- Y

LEGENDCrusher OversizeCrusher UndersizeConcentrator OversizeConcentrator UndersizeAgglomerator OversizeAgglomerator UndersizeKiln OversizeKiln Undersize

PARTICLE SIZE-DISTRIBUTIONActive Taconite Processing Facilities

Wt.

Perc

ent U

nder

size

Y

Figure 21. Particle size distribution related to multi-event comminution processes from active plants: Wt. % oversize versus undersize.



0.1

1

10

100W

t. Pe

rcen

t Fra

ctio

n O

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ize

PARTICLE SIZE-DISTRIBUTIONCumulative Fractions by Weight Oversize

Figure 22. Particle size distribution ‘best-fit’ curve fitting - Cumulative fractions by weight oversize.


CONCLUSIONS To characterize the amounts of aerosol PM within the six taconite processing facilities located on the MIR in northeastern Minnesota, the NRRI conducted a total of 14 separate PM sampling events between March 2009 and June 2010. All six facilities were sampled at least once during active operation (11 total). Three plants were sampled when plants were shut down (inactive) in 2009. Two of the plants (Plant A and Plant F) were sampled three times each during active operation. Sampling between plants occurred randomly and during both summer season (May through October) and winter season (November through April). Each of the sampling events consisted of two-hour sample collections at four similar locations in each facility, including: 1) fine crusher; 2) concentrator – magnetic separator; 3) agglomerator – balling drums/discs; and 4) kiln – pellet discharge. These locations were chosen within the plants based on significant physical or chemical changes to the raw material, as related to particle size and/or a change in mineralogical characteristics. Based on the consistency of the geology of the BIF and the similarities of mining and processing the ore, statistical power of analysis was achieved through the ten cumulative sample series (90% confidence level) collected in the five most-western plants. Four additional sample series (95% confidence level) were collected from the sixth plant on the east end of the BIF, where the geology/mineralogy of the iron formation has been modified due to thermal metamorphism associated with the intrusion of the Duluth Complex approximately 1.1 billion years ago. Findings Aerosol PM samples were collected and analyzed from all six processing plants to provide the study

with an understanding of the PM concentrations and relative proportions within the four major process areas of the plants. The number of samples (three) collected during total plant shutdown (inactive plant samples) were

insufficient for making reliable determinations of statistical significance. For sampling conducted during plant inactivity (inactive plants), the overall average concentrations of

MOUDI total PM within each of the process areas do not vary considerably (crusher (169.26 µg/m3), concentrator (191.63 µg/m3), agglomerator (178.80 µg/m3), kiln (177.06 µg/m3: see Table 14 and Fig. 9). Average PM2.5 concentrations in inactive plants was found to be higher in the concentrator process area (120.89 µg/m3) than in the crusher (93.86 µg/m3), agglomerator (70.23 µg/m3), and kiln process areas (76.71 µg/m3) Table 14 and Fig. 9). Statistical ranking of the plant process areas by total MOUDI PM concentrations during plant activity

(active plants, 11 samples) indicated: the kiln and agglomerator process areas have significantly greater average MOUDI Total PM

than the crusher and concentrator areas (kiln (7357.82 µm3), agglomerator (5272.63 µm3), crusher (735.88 µm3), concentrator (578.28 µm3) (Table 15 and Fig. 10);

Ranked from largest to smallest, average concentrations of PM2.5 in the different plant process areas are: 1) kiln (4985.66 µg/m3), 2) agglomerator (420.89 µg/m3), 3) crusher (277.80 µg/m3), and 4) concentrator (201.49 µg/m3; Table 15 and Fig. 10); and

the coarser PM fraction (>PM2.5) was significantly greater in the kiln and agglomerator than the crusher and concentrator (Fig. 10).

The PM data from active plant samples comparing western plants (Plants B, C, D, E, and F) – combined eight sample sets total) with Plant A (three sample sets), indicated that most process locations showed no significant difference in PM1, PM2.5, PM10, and coarse PM (Table 20). Only the Plant A kiln had significantly greater amounts of coarse PM relative to Plant F. These two plants are located in different geographic areas of the MIR which contain different mineral assemblages and degrees of thermal metamorphism.


HIGHLIGHTED FINDINGS The following discussion summarizes, by process location, plants having the greatest and lowest abundance of PM. As well, the mean PM concentration for all plants for that process location is indicated. MOUDI Total PM Concentrations Fine Crusher The highest MOUDI total PM concentration found in the area of the fine crusher during plant activity was 1570.79 µg/m3 at Plant F (Table 16). This can be compared to an overall average MOUDI total PM concentration for the active crusher process area in all plants of 735.88 µg/m3. The lowest total MOUDI PM concentration measured in the area of the fine crusher was 278.39 µg/m3 at Plant D. Concentrator The concentrator process area contained the lowest average concentrations of total MOUDI PM in the four process area locations that were sampled in active plants (578.28 µg/m3; Table 15). A total MOUDI PM concentration of 885.82 µg/m3 that was measured at Plant A was the highest MOUDI total PM for the active concentrator process area. The average total MOUDI PM concentration for the active concentrator process area in all active plants was 578.28 µg/m3. The concentrator process area with the lowest total MOUDI PM concentration was Plant C, with a total MOUDI PM concentration of 141.01 µg/m3. Agglomerator For the agglomerator process area, the highest total MOUDI PM concentration during plant activity was 16,684.25 µg/m3 at Plant A (Table 16). This can be compared with the average total MOUDI PM concentration in all active plants of 5272.63 µg/m3. The lowest total MOUDI PM concentration measured in the active agglomerator process area was 1287.18 µg/m3 at Plant C. Kiln The kiln process area contained the highest average concentration of total MOUDI particulate matter. The highest concentration of total PM in an active kiln process area, 20,980.17 µg/m3, occurred at Plant E (Table 16). The average total MOUDI PM concentration for the kiln process area in all active plants was 7357.82 µg/m3. The active kiln process area with the lowest concentration of total MOUDI PM was Plant C, 445.53 µg/m3. PM2.5 Concentrations

Specific PM levels in the PM2.5 fraction (measured in µg/m3 – and by representative percent of total sample) calculated from samples collected using the MOUDI sampler in the four process areas of the active plants are also listed by highest, lowest, and average concentrations for each of the plant process areas sampled. These measurements are also illustrated in Figure 8. Fine Crusher

In the fine crusher process area, the highest PM2.5 concentration measured during plant activity was 577.31 µg/m3 at Plant A (Table 16). This can be compared with an average PM2.5 concentration in the fine crusher area measured in all active plants of 277.80 µg/m3. The lowest PM2.5 concentration measured in the fine crusher process area of an active plant was 118.09 µg/m3 at Plant C. The average PM2.5 concentration represents approximately 42% of the average total PM concentration measured during plant activity for all plants (Table 16).


Concentrator The concentrator (magnetic separation) process area contained, on average, the lowest concentration of PM2.5 (Table 15). The highest PM2.5 concentration of 311.41 µg/m3 was measured at the active concentrator process area in Plant F. The overall average PM2.5 concentration for the concentrator process area measured in all active plants was 201.49 µg/m3. The active concentrator process area with the lowest concentration of PM2.5 was measured at Plant C, 72.09 µg/m3. In terms of percentage, the average PM2.5 fraction represents 37.6% of the average total PM in the concentrating area (Table 16). Agglomerator The highest PM2.5 concentration in an active agglomerator process area, 944.29 µg/m3, was measured at Plant A. The overall average PM2.5 concentration in the agglomerator process area measured in all active taconite processing plants is 420.89 µg/m3. The active agglomerator process area sample with the lowest PM2.5 concentration was also from Plant A, 239.28 µg/m3. The average PM2.5

concentration in the agglomerator process area represents 11.4% of total particulate matter (Table 16). Kiln The highest PM2.5 concentration in the discharge area of an active kiln process area was 948.76 µg/m3 from Plant D. The average PM2.5 concentration in the active kiln process area for all plants sampled is 495.66 µg/m3. The lowest PM2.5 concentration measured in the active kiln process area was 188.76 µg/m3 at Plant C. The average PM2.5 concentration in the kiln is approximately one third that measured in the crushing and concentrating areas, averaging 15.7% of the total particulate matter (Table 16). Summary of Plant Gravimetric Data

Figures 23 and 24 illustrate bar graphs depicting average MOUDI total PM concentration and their average PM2.5 concentrations for both active and inactive plants. These graphs were constructed by averaging all samples collected in the respective process areas of each plant over the course of this study. Averages for active and inactive plant processes were calculated independently. In general, active plant process locations were characterized by higher concentrations of PM than inactive plant process locations. In summary, the characterization of PM within the plants indicates that this specific type of work environment is often dusty and associated with high concentrations of particulate matter.


Figure 23. Comparison of samples (averaged by location) by processing plant – MOUDI totals (Weight/Volume Air – µg/m3).


Figure 24. Comparison of samples (averaged by location) by processing plant – PM2.5 fraction (Weight/Volume Air – µg/m3).


Further work Follow-up studies and monitoring of PM levels in all locations of individual plants are recommended. Review and implementation of engineering solutions may result in dust mitigation within the plants. ACKNOWLEDGEMENTS The Minnesota Legislature is gratefully acknowledged for providing base funding for the Minnesota Taconite Workers Health Study (MTWHS), as are the Iron Range Legislative Delegation for their efforts and advocacy for securing that funding. The Natural Resources Research Institute (NRRI) is also acknowledged for providing significant supplemental project support via the Permanent University Trust Fund (PUTF). The NRRI would also like to thank our colleagues at the University of Minnesota School of Public Health (SPH) – in particular, study leaders Drs. John Finnegan and Jeffrey Mandel. As our SPH colleagues have stated, this undertaking was the result of the concerted effort of the entire Lung Health Partnership, and contributors to this effort were many. The NRRI Particle and Material Characterization Group would like to thank the following industry representatives for their time and patience, and also for the safe access within the taconite processing facilities: Mr. Kelly R. (Rob) Campbell – Industrial Hygiene Specialist/Cliffs Natural Resources, for access to Northshore and Utac; Ms. Karla L. Heritage-McKenzie – Safety Manager/ArcelorMittal, for access to Minorca; Mr. Kent Swanson – Staff Supervisor/Safety & I.H./U.S. Steel, for access to Minntac and Keetac; and Ms. Stephanie Bigelow – Safety Representative (along with Rob Campbell), for access to Hibtac. The NRRI’s Particle Study project team extends additional thanks to several individuals for their contributions and input, starting with Anda Bellamy, editor and publications specialist. Anda’s editing, organizing, and assembly of the team’s final reports was a huge task. Next is Tamara Diedrich, who initiated and oversaw many key components of the NRRI’s early project work. We also wish to thank the members of the NRRI Particle Study Science Advisory Board (SAB), composed of D. Wayne Berman (AEOLUS Inc.), Gregory Meeker (United States Geological Survey – USGS), Paul Middendorf (National Institute of Occupational Safety and Health – NIOSH), and Daniel Vallero (U.S. Environmental Protection Agency – USEPA) who provided guidance, recommendations, and constructive criticism during the course of this work; their collective inputs were of significant assistance to the NRRI team, and their advisory role was much appreciated. A deep expression of gratitude is given to Professor Emeriti Dale Lundgren (University of Florida) and the late Virgil Marple (University of Minnesota), as well as Bernard Olson (University of Minnesota), Bryan Bandli (University of Minnesota Duluth), and Francisco Romay (MSP Corporation – MOUDI), for the key roles they played advising the technical aspects of our aerosol science-based experimental designs, sampling, and particulate matter (PM) analysis and characterization. Special thanks are also extended to former NRRI team members Devon Brecke and Megan Schreiber, who played important sample collection and laboratory support roles, and to the NRRI’s Meijun Cai for her statistical review and analysis of the project’s community, background, and taconite facility datasets. We would also like to thank the dedication and hard work of all the student workers who contributed to this effort over the years, including: Alanna Schwanke, Chris Bicknese, April Severson, Allison Severson, Stuart Kramer, and Matt Chaffee. Minnesota agencies are also thanked for providing feedback to the NRRI’s work. They include the MPCA, Minnesota Department of Health (MDH), Minnesota Department of Natural Resources (MDNR), and the Department of Iron Range Resources & Rehabilitation (DIRRR). Lastly, the NRRI investigators wish to acknowledge two individuals, starting with the late Dr. Phil Cook of the EPA’s Mid-Continent Ecology Division in Duluth, MN. The history of the issues addressed by the Minnesota Taconite Workers Health Study – going back to the 1970s – necessarily includes Dr. Cook and the key role he played. The investigators also give special recognition to the late Tom Rukavina, who was a strong legislative and personal advocate for the study, not only for the University of Minnesota but for the people of Minnesota’s Mesabi Iron Range.


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APPENDICES Appendices are PDF files attached to this document as follows: Appendix A – Plant sample locations Appendix B – Plant Field Blank Gravimetric Analysis

Appendix A: Plant Sample Locations

(Sorted by plant and plant processing area)

Each of the taconite processing plant PM sampling locations is illustrated, describing and showing the approximate location of sampling equipment, i.e., MOUDI impactor and vacuum pump tote, with relevance to nearby major equipment. Site locations were based on centralizing the sampling equipment horizontally between lines and vertically between multiple floors at each of the four process locations. A standard power outlet was also an important component in site selection. Note: all figures are approximate and not necessarily to scale.

KeetacSecondary Crusher Sample Location

KeetacConcentrator/MagneticSeparator Sample Location

KeetacKiln/Pellet Discharge Sample Location

Level 4/ 4th f l or, crusher #2 (~20 feet), adjacent to crusher motor and oil cooler.

Second f l oor ( ~15feet from kiln discharge) near dust collector door #33.

Between lines4 and 5 (~30 feet from each).

KeetacAgglomerator Sample Location

Between drums9 and 10 at ball/pellet exit (~20 feet).

#2 Crusher

oil cooler

MOUDI

vacuum

pump

MOUDIvacuum

pump

Line 4 Line 5

MOUDI

vacuum

pumpDrum 9

Drum 10

MOUDI

vacuum

pump

KilnPellet

Discharge

walkway

walkw

ay

HibtacSecondary Crusher Sample Location

HibtacConcentrator/MagneticSeparator Sample Location

HibtacKiln/Pellet Discharge Sample Location

Between crushers#2 (~10 feet) and #1,adjacent to f l oor pi pes andi ndction motor.

Between Furnaces#1 and #2 (~20 feet) from end at pellet discharge.

Between lines3 and 4 (~25 feet from each) and adjacent to support post B11.

HibtacAgglomerator Sample Location

Between drumsFand Gat ball/pellet exit (~10 feet).

#2 Crusher

induction

MOUDIvacuum

pump

MOUDIvacuumpump

rod mill #4 rod mill #3

MOUDIvacuum

pump

MOUDIvacuum

pump

Furnace #2

motor

#1 Crusher

inductionmotor

ladderpipeon

f l oor

postB11

post

conveyor belt with pellets

Drum GDrum F

Furnace #1

walkway

walkw

ay

wind

ow

walkwaywalkway

MinntacSecondary Crusher Sample Location

MinntacConcentrator/MagneticSeparator Sample Location

MinntacKiln/Pellet Discharge Sample Location

Forth f l oor btween crushers#02-1520 (~15 feet) and #01-1520,against wall.

Located at the pellet discharge (~15 feet) of kiln #7.

Adjacent to rod mill line 15 (~25 feet) between postsW22 and W20.

MinntacAgglomerator Sample Location

Level 4, between drums6-3 and 6-2 at ball/pellet exit (~10 feet).

#02-1520 Crusher

MOUDIvacuum

pump

rod mill #15

MOUDIvacuum

pump

#01-1520 Crusher

postW20

Drum 6-2Drum 6-3

walkway

postW22

MOUDI

vacuum

pump

MOUDI

vacuum

pump

Kiln #7Pellet

Discharge

UtacSecondary Crusher Sample Location

UtacConcentrator/MagneticSeparator Sample Location

UtacKiln/Pellet Discharge Sample Location

Second level on walkway between forth-stage 4Fcrusher (~40 feet) and third-stage 5Ccrusher (~15 feet), near old of ce.

Kiln - Line #2 (~15 feet) to the right of pellet discharge.

Located in middle of area, adjacent to column G-25,between the roughers(~30 feet) and ball mill #3 (~50 feet).

UtacAgglomerator Sample Location

Between drums8 and 9 at ball/pellet exit (~15 feet).

4FC

rush

er

MOUDIvacuum

pump

MOUDIvacuum

pump

Roug

her

BallM

ill#3

MOUDI

vacuum

pump

Drum 8

Drum 9

MOUDIvacuum

pump

Kiln - Line #2Pellet

Discharge

walkway

walkw

ay

Fort

h-St

age

5CCrusher

Third-Stage

old of fce

G-25

Roug

her

Roug

her

walkw

ay

walkway

Minorca Secondary Crusher Sample Location

Minorca Concentrator/MagneticSeparator Sample Location

Minorca Kiln/Pellet Discharge Sample Location

Three f li htsof stairsup from the control room, between crusher #5 and crusher #4 (~20 feet).

Located at the pellet discharge (~20 feet) of Furnace #F4M39.

Main f l oor ext to eye wash and men’swashroom, (~25 feet) between rod mills.

Minorca Agglomerator Sample Location

Between balling disksC, D, Eand F,nearest to balling disk D’sopen face (~25 feet).

#5 Crusher

MOUDIvacuum

pump

rod mill

MOUDI

vacuum

pump

#4 Crusher

Balling Disk DBalling Disk C

MOUDI

vacuum

pump

MOUDI

vacuum

pumpFurnace #F4M39

PelletDischarge

post

rod mill

men’s washroom

stairs

post

Balling Disk E Balling Disk F

walkway

Northshore Secondary Crusher Sample Location

Northshore Concentrator/MagneticSeparator Sample Location

Northshore Kiln/Pellet Discharge Sample Location

Upper level and central to all crushers,adjacent column D39, acrossfrom crusher 312-003 (~25 feet).

Between furnaces11 and 12, (~15 feet) from end at pellet discharge.

Centrally located on upper level next to rod mill 45E(~50 feet), adjacent to conveyor 107 N & S.

Northshore Agglomerator Sample Location

Between drumsCand D at ball/pellet exit (~10 feet).

Crusher 312-003

pipe

vacuum

pump

MOUDI

vacuumpump

rod mill 45E

stair well

MOUDIvacuum

pump

MOUDIvacuum

pump

Furnace #12

Drum DDrum C

Furnace #11

walkway walkw

ay

wind

ow

walkway

MOUDIpostD39

door

walkway

door

ladd

er

conveyor107 N & S

walkway

drivew

ay

railing

control panaldrum C

railing

control panaldrum D

railing

APPENDIX B: Plant Field Blank Gravimetric Analysis

(Sorted by plant processing area and then date; weights in µg)

NRRI/RI‐2019/29 – Taconite Facilities Gravimetric Analysis 9

PLANT PARTICULATE MATTER SAMPLING – FIELD BLANK WEIGHT DIFFERENCES (mg)

Date Plant Process Series Pre Wt. Ave. Post Wt. Ave. Wt. Diff.

Polycarbonate w/Al foil back and grease

5/11/2010 A Crusher 1771 5.568 5.617 0.049

5/25/2010 E Crusher 1861 0.423 0.498 0.075

6/8/2010 F Crusher 1941 1.675 1.652 -0.023

6/22/2010 C Crusher 2021 6.390 6.293 -0.097

6/30/2010 B Crusher 2101 1.979 2.002 0.023

5/11/2010 A Concentrator 1781 0.799 0.877 0.078

5/25/2010 E Concentrator 1871 5.297 5.347 0.049

6/8/2010 F Concentrator 1951 -4.452 -4.446 0.006

6/22/2010 C Concentrator 2031 2.433 2.351 -0.082

6/30/2010 B Concentrator 2111 3.269 3.289 0.020

5/11/2010 A Agglomerator 1991 4.247 4.315 0.068

5/25/2010 E Agglomerator 1881 2.707 2.754 0.047

6/8/2010 F Agglomerator 1961 10.276 10.086 -0.191

6/22/2010 C Agglomerator 2041 2.910 2.951 0.041

6/30/2010 B Agglomerator 2121 4.198 4.233 0.034

5/11/2010 A Kiln 1801 2.231 2.264 0.033

5/25/2010 E Kiln 1891 5.625 5.679 0.054

6/8/2010 F Kiln 1971 5.334 5.355 0.021

6/22/2010 C Kiln 2051 5.556 5.608 0.052

6/30/2010 B Kiln 2131 6.157 6.195 0.038

0.015 Average

0.067 Standard Deviation

0.004 Variance




Polycarbonate

5/11/2010 A Crusher 1771 13.701 13.742 0.041

5/25/2010 E Crusher 1861 14.036 14.098 0.062

6/8/2010 F Crusher 1941 13.601 13.624 0.023

6/22/2010 C Crusher 2021 13.340 13.372 0.032

6/30/2010 B Crusher 2101 13.444 13.471 0.027

5/11/2010 A Concentrator 1781 13.732 13.792 0.059

5/25/2010 E Concentrator 1871 14.249 14.304 0.055

6/8/2010 F Concentrator 1951 12.788 12.807 0.019

6/22/2010 C Concentrator 2031 14.182 14.217 0.035

6/30/2010 B Concentrator 2111 13.244 13.267 0.023

5/11/2010 A Agglomerator 1991 11.919 11.992 0.074

5/25/2010 E Agglomerator 1881 13.081 13.132 0.051

6/8/2010 F Agglomerator 1961 13.080 13.105 0.026

6/22/2010 C Agglomerator 2041 13.417 13.454 0.038

6/30/2010 B Agglomerator 2121 12.859 12.889 0.030

5/11/2010 A Kiln 1801 12.849 12.877 0.028

5/25/2010 E Kiln 1891 14.516 14.569 0.053

6/8/2010 F Kiln 1971 13.401 13.428 0.027

6/22/2010 C Kiln 2051 11.920 11.957 0.037

6/30/2010 B Kiln 2131 13.548 13.584 0.036

0.039 Average


0.000 Variance




PTFE - Teflon®

5/11/2010 A Crusher 1771 18.289 18.309 0.020

5/25/2010 E Crusher 1861 12.516 12.563 0.047

6/8/2010 F Crusher 1941 10.115 10.131 0.016

6/22/2010 C Crusher 2021 10.123 10.137 0.014

6/30/2010 B Crusher 2101 11.921 11.960 0.039

5/11/2010 A Concentrator 1781 16.701 16.934 0.233

5/25/2010 E Concentrator 1871 11.713 11.750 0.037

6/8/2010 F Concentrator 1951 11.426 11.448 0.022

6/22/2010 C Concentrator 2031 13.105 13.127 0.021

6/30/2010 B Concentrator 2111 11.736 11.768 0.032

5/11/2010 A Agglomerator 1991 20.145 20.181 0.036

5/25/2010 E Agglomerator 1881 13.860 13.891 0.031

6/8/2010 F Agglomerator 1961 13.755 13.774 0.018

6/22/2010 C Agglomerator 2041 12.124 12.145 0.021

6/30/2010 B Agglomerator 2121 14.219 14.239 0.020

5/11/2010 A Kiln 1801 14.350 14.368 0.018

5/25/2010 E Kiln 1891 11.422 11.452 0.029

6/8/2010 F Kiln 1971 11.729 11.748 0.019

6/22/2010 C Kiln 2051 13.799 13.832 0.033

6/30/2010 B Kiln 2131 12.842 12.886 0.044

0.038 Average


0.002 Variance


PARTICULATE MATTER SAMPLING - LABORATORY BLANK WEIGHT DIFFERENCES (mg)

Date Site Series Pre Wt. Ave. Post Wt. Ave. Wt. Diff.

Polycarbonate

4/8/2010 F 1581 13.739 13.718 -0.022

4/20/2010 Silver Bay H.S.* 1661 11.748 11.754 0.007

4/29/2010 Silver Bay H.S.* 1671 12.212 12.217 0.005

5/11/2010 A 1771 13.395 13.434 0.040

5/25/2010 E 1861 13.254 13.306 0.052

6/8/2010 F 1941 12.587 12.608 0.021

6/22/2010 C 2021 12.495 12.522 0.027

6/30/2010 B 2101 13.694 13.717 0.023

9/30/2010 Keewatin* 2201 12.803 12.783 -0.021

11/23/2010 Duluth* 2261 14.573 14.510 -0.063

2/15/2011 MPLS* 2301 11.384 11.395 0.011

5/12/2011 MPLS* 2331 11.123 11.117 -0.005

0.006 Average

*Community/backgroun

d location 0.031 Standard Deviation

0.001 Variance

Collection and Gravimetric Analysis December 2019

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