Utrecht University · Utrecht University Masters Thesis Faculty of Geosciences E ect of Mining on...

Utrecht University

Masters Thesis

Faculty of Geosciences

Effect of Mining on Fine SedimentGeochemistry in the Horsefly River

Catchment, British Columbia, Canada

A Study on Black Creek Mine

Author:Deirdre E Clark

Supervisor:Dr. Marcel van der

Perk

12 July 2013

Abstract

Canada has 7% of the world’s renewable freshwater and is also one of the top worldproducers of metals like uranium, gold and zinc. Consequently, it is not surprisingthat monitoring the environmental impacts of the country’s mining industry is inthe interest of many. Mining exposes metals in sediments to weathering allowingthe sediments to erode and redeposit elsewhere, most commonly in rivers, streamsand lakes. As bed sediments from these surface waters retain, store or release heavymetals, those metals can be further transported, deposited and remobilised ineither particulate or dissolved form. Previous studies have shown that most metalsare in particulate form, specifically in the fine (<63 µm) sediment fraction.

Sediment geochemistry of gold mining was characterised and quantified to de-termine the spatial effects in the Horsefly catchment area of British Columbia,Canada, for the reason that the region has been extensively mined since the nine-teenth century. Samples of channel bed sediments were collected from a creeknear the abandoned Black Creek mine that drains into the Horsefly River. Sedi-ment was also resuspended in the Horsefly River and collected with buckets anda continuous centrifuge. Both types of sediment were used to investigate spatialvariability and trace any effects from the mine down along the creek and river.Heavy metal concentrations (arsenic, cadmium, copper, selenium and zinc) of thefine (<63 µm) sediments for each sample were quantified using aqua regia digestionand BCR’s (European Community Bureau of Reference) modified sequential ex-traction procedure and analysed by ICP-OES (inductively coupled plasma opticalemission spectrometry). The percentage of organic matter and particle sizes werealso determined. There were elevated levels of arsenic associated with the BlackCreek mine in addition to local increases in arsenic concentrations along the BlackCreek. Despite this, no recent mining effects were observed along the HorseflyRiver, which the Black Creek drains into, likely due to the mine’s inactive statusand small size.

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Horsefly River, British Columbia.

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Acknowledgements

I want to thank my thesis supervisor, Marcel van der Perk from Utrecht University,for helping to organise this project and his guidance throughout the past year.Thank you especially to Marjolein Vogels for your vital help as a fieldwork partneras well as a companion on our big North American road trip! Phil Owens and EllenPettigrew from the University of Northern British Columbia were also instrumentalduring and after fieldwork; thank you for your added advice and the opportunityto use the Quesnel River Research Centre’s resources.

I want to thank Ben Anderson for your tremendous assistance and support duringfieldwork on top of taking charge of the particle size analysis. Thanks goes toSamuel Albers, Laszlo Enyedy, Adam Simons and Alex Koiter for your help andadvice with fieldwork and sample preparation. Thank you to Guy Nesbitt for yourgenuine interest in the project.

Thanks also to Thilo Behrends and Dineke van de Meent-Olieman from UtrechtUniversity for your support and guidance in the geochemistry laboratory and theopportunity to learn some new methods!

Lastly, thanks to my family in Canada and America and my friends in New Jerseyand Utrecht for your interest and support.

This research was made possible by the financial support of the Association ofCanadian Studies, University of Northern British Columbia and Utrecht Univer-sity.

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Contents

1 Introduction 11.1 Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.2.1 Climate, Soil & Vegetation . . . . . . . . . . . . . . . . . . . 41.2.2 Geology & Placer Deposits . . . . . . . . . . . . . . . . . . . 61.2.3 Black Creek Placers . . . . . . . . . . . . . . . . . . . . . . . 71.2.4 Fish & Wildlife . . . . . . . . . . . . . . . . . . . . . . . . . 111.2.5 History & Landuse . . . . . . . . . . . . . . . . . . . . . . . 12

1.3 Mining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131.3.1 Quesnel Case Studies . . . . . . . . . . . . . . . . . . . . . . 151.3.2 Wales Case Study . . . . . . . . . . . . . . . . . . . . . . . . 15

1.4 Description of Heavy Metals . . . . . . . . . . . . . . . . . . . . . . 151.4.1 Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151.4.2 Cadmium . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161.4.3 Copper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171.4.4 Selenium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171.4.5 Zinc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.5 Metals in Aquatic Envrionments . . . . . . . . . . . . . . . . . . . . 181.6 Geochemical Phases of Metals . . . . . . . . . . . . . . . . . . . . . 19

2 Methods 222.1 Sampling Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . 222.2 Sampling Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2.2.1 Resuspended Sediment . . . . . . . . . . . . . . . . . . . . . 222.2.2 Source Material & Bed Sediment . . . . . . . . . . . . . . . 252.2.3 Sample Preparation . . . . . . . . . . . . . . . . . . . . . . . 26

2.3 Organic Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.4 Particle Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272.5 Geochemical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.5.1 Aqua Regia Digestion . . . . . . . . . . . . . . . . . . . . . . 29

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2.5.2 Sequential Extraction . . . . . . . . . . . . . . . . . . . . . . 292.6 Statistical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3 Results & Discussion 313.1 pH and EC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313.2 Particle Size Distribution . . . . . . . . . . . . . . . . . . . . . . . . 323.3 Organic matter content . . . . . . . . . . . . . . . . . . . . . . . . . 343.4 Comparison Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.4.1 Collection Methods . . . . . . . . . . . . . . . . . . . . . . . 353.4.2 Laboratory Analysis . . . . . . . . . . . . . . . . . . . . . . 35

3.5 Total Metal Concentrations & Metal Speciation . . . . . . . . . . . 373.5.1 Aluminum . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373.5.2 Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.5.3 Cadmium . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433.5.4 Copper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463.5.5 Selenium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503.5.6 Zinc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

4 Conclusions 58

Bibliography 61

A Detection limits of ICP-OES and ICP-MS 66

B 100% Stacked Columns of Sequential Extraction Procedure 68

C Observed Concentrations from Aqua Regia Digestion and Se-quential Extraction 73

D Observed Concentrations from Geochemical Phases of Sequen-tial Extraction 81

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List of Figures

1.1 Study area of Horsefly River watershed in British Columbia, Canada(Modified from Surveys & Mapping Branch, 1976). . . . . . . . . . 3

1.2 Mean monthly temperatues and precipitation of Horesfly, BritishColumbia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.3 Geology of central Quesnel Belt British Columbia, legend on nextpage (Modified from Bailey, 1987). . . . . . . . . . . . . . . . . . . 8

1.4 Supergene enrichment process (Modified from Nesse, 2000). . . . . . 101.5 Placer deposits (Modified from Marshak, 2005). . . . . . . . . . . . 111.6 Panning for gold in the Horsefly River (Horsefly Historical Society,

1981). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.7 Stouts Gulch mine adjacent to Lowhee Creek in Cariboo region of

British Columbia. This is an example of what Black Creek minemight have looked like with hydraulic operations (Eyles & Kocsis,1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.8 The hyporheic zone of a stream (Winter et al. , 1998). . . . . . . . 191.9 Internal processes that affect the formation of particulate metals in

the sediments (Modified from Luoma & Rainbow, 2008). . . . . . . 20

2.1 Sample locations, refer to Table 2.1 for more details on each location(Modified from Figure 1.1). . . . . . . . . . . . . . . . . . . . . . . 23

2.2 Abandoned open pit of Black Creek mine (left); remnants of woodensluice boxes in Black Creek (right). . . . . . . . . . . . . . . . . . . 23

2.3 Horsefly River downstream of Black Creek. . . . . . . . . . . . . . . 242.4 Collecting resuspended sediment at HR 6 (left); centrifuging, de-

canting, and air-drying of sediment samples (right). . . . . . . . . . 252.5 Grinding of fine sediments with mortar and pestle. . . . . . . . . . 262.6 Loss of ignition method to measure percentage of organic matter. . 272.7 Applying hydrogen peroxide to burn off organic matter before par-

ticle size analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272.8 Modified BCR’s three step sequential extraction. . . . . . . . . . . . 28

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2.9 Sediment core from Horsefly River floodplain (Vogels, 2013). . . . . 28

3.1 pH and EC of Black Creek and Horsefly River sites. . . . . . . . . . 313.2 Al concentrations [%] plotted against the percentage of particles

between 2 µm from all samples. . . . . . . . . . . . . . . . . . . . . 323.3 Percentage of particles below 2 µm of Black Creek and Horsefly

River sites (D = duplicate). . . . . . . . . . . . . . . . . . . . . . . 333.4 Percentage of organic matter. . . . . . . . . . . . . . . . . . . . . . 343.5 Al concentrations [%] from aqua regia digestion and sequential ex-

traction procedure of Black Creek and Horsefly River sites. Back-ground concentrations from the sediment core are plotted as a ref-erence value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.6 Percentage of Al measured in the first three steps (exchangeable/carbonate,Fe/Mn oxides, sulphide/organic) of the sequential extraction proce-dure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.7 As concentrations [mg/kg] plotted against Al concentrations [%] forall sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.8 As concentrations [mg/kg] normalised against Al concentrations[%] from aqua regia digestion and sequential extracture procedure.Background concentrations from the sediment core are plotted as areference value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.9 Cd concentrations [mg/kg] plotted against Al concentrations [%] forall sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.10 Cd concentrations [mg/kg] normalised against Al concentrations[%] from aqua regia digestion and sequential extracture procedure.Background concentrations from the sediment core are plotted as areference value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

3.11 Cu concentrations [mg/kg] plotted against Al concentrations [%] forall sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

3.12 Cu concentrations [mg/kg] normalised against Al concentrations[%] from aqua regia digestion and sequential extracture procedure.Background concentrations from the sediment core are plotted as areference value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

3.13 Percentage of Cu measured in the first three steps (exchangeable/carbonate,Fe/Mn oxides, sulphide/organic) of the sequential extraction proce-dure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

3.14 Se concentrations [mg/kg] plotted against Al concentrations [%] forall sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

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3.15 Se concentrations [mg/kg] normalised against Al concentrations [%]from aqua regia digestion and sequential extracture procedure. Back-ground concentrations from the sediment core are plotted as a ref-erence value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

3.16 Zn concentrations [mg/kg] plotted against Al concentrations [%] forall sites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

3.17 Zn concentrations [mg/kg] normalised against Al concentrations[%] from aqua regia digestion and sequential extracture procedure.Background concentrations from sediment core plotted as a refer-ence value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

3.18 Percentage of Zn measured in the first three steps (exchangeable/carbonate,Fe/Mn oxides, sulphide/organic) of the sequential extraction proce-dure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

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List of Tables

2.1 Description of samples. . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.1 Linear regression analysis of Al [%] vs particles below 2 µm [%]. . . 323.2 Metal concentrations [mg/kg] between the sample collection meth-

ods for resuspended sediment. . . . . . . . . . . . . . . . . . . . . . 353.3 Concentrations [mg/kg] and correlation coefficient, r, between aqua

regia digestion results from laboratories in Vancouver, Canada andUtrecht, the Netherlands. . . . . . . . . . . . . . . . . . . . . . . . . 36

3.4 Linear regression analysis of As [mg/kg] vs Al [%]. . . . . . . . . . . 403.5 Linear regression analysis of Cd [mg/kg] vs Al [%]. . . . . . . . . . 433.6 Linear regression analysis of Cu [mg/kg] vs Al [%]. . . . . . . . . . 463.7 Linear regression analysis of Se [mg/kg] vs Al [%]. . . . . . . . . . . 503.8 Linear regression analysis of Zn [mg/kg] vs Al [%]. . . . . . . . . . . 54

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Chapter 1

Introduction

Canada’s mining industry, according to the Mining Association of Canada, hasbeen a major reason why the past years’ economic turmoil had not affected Canadato the same extent as in other developed countries. As one of the top worldproducers of metals and minerals, e.g. uranium, nickel, aluminum, diamonds, goldand zinc, Canada’s mining sector consists of 220 operating mines, 33 smelters andrefineries and 320,000 employees (Brown, 2002; Costella, 2013).

Mining exposes metals in sediments to weathering thus allowing these sedimentsto erode and redeposit elsewhere. Surface waters like rivers and streams mostcommonly receive metal-containing wastes from mining sites. Bed sediments ofthese waters retain, store or release significant amounts of nutrients and heavymetals. Those metals are transported, deposited and remobilised in waters ineither particulate or dissolved form. Several studies report that roughly 90% ofthe metals transported are in particulate form, especially in the fine (<63 µm)sediment fraction (Hale, 1994; Luoma & Rainbow, 2008; Smith & Owens, 2010;van der Perk, 2006).

Canada contains 7% of the world’s freshwater resources with the Canada WaterAct (1970) providing the proper framework to conserve, develop and utilise theseresources (Environment Canada, 2013). Requiring environmental assessments ofmines is a vital step to understand the potential impacts on Canada’s freshwatersystems. Unfortunately, projects are regularly approved despite incomplete re-search on their environmental impacts, as was the case for the proposed Red Chrismine in northwest British Columbia. A recent report published had indicated thelack of understanding of how 300 million tonnes of tailings (mine waste) wouldaffect the watershed, even though the project had passed assessment several yearsprevious (Pollen, 2013).

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Environment Canada is calling for stricter federal rules and regulations to helpprevent further water pollution caused by mines especially for heavy metals likeselenium (Environmental Technology, 2013). A study sponsored by Glacier Na-tional Park reported that Elk Valley, also in British Columbia, contains seleniumlevels ten times the amount of the neighbouring Flathead River basin. The fiveactive coal mines based here are run by Tech Resources, who claim that theselevels are not significant enough to affect fish and harm drinking water supplies.Nevertheless the concerns from local communities and organisations have led theprovince’s Ministry of Environment to request the company’s water monitoringand treatment plans (Tam, 2013).

The concentrations of metals in aquatic systems are important to consider asaquatic biota depend on the proper acquisition of many trace metals like copper,iron, managanese and zinc for growth; too high a concentration can actually betoxic. This can severely affect aquatic biota such as phytoplankton and bacteria,which are highly susceptible to abiotic geochemical processes (Morel, 1983).

Mining in British Columbia has been prevalent since the 1850s and the first suc-cessful gold panning expeditions. The settlements in the Cariboo region rapidlygrew and prospered establishing communities near active mine sites and on wa-terways such as Quesnel Lake and Horsefly River. Some towns like Quesnel Forkshave since died out with the passing of the gold rush, but communities like Horseflysurvived by relying on other means of income from trapping, logging and ranching(BC Parks, 2013; Horsefly Historical Society, 1981).

A study conducted by Smith & Owens (2010) concludes that mining and loggingactivities in the area have a greater influence on metals and nutrients than agri-culture. Karimlou (2011) and van Lipzig (2011) determine that active mining isinfluencing the fine sediment geochemistry of the Quesnel catchment. These stud-ies confirm that mining indeed promotes the release of metals into surroundingsystems (Drever, 1997; Luoma & Rainbow, 2008).

1.1 Objective

This study aims to examine the downstream effects of small-scale gold miningon the geochemistry of fine (<63 µm) river sediments. The chosen site was anabandoned gold mine two km upstream from the Horsefly River along the BlackCreek (52 ◦18’45” N/121 ◦5’34” W). The Horsefly River catchment is located in theCariboo region of British Columbia in Canada and is part of the larger Quesnelwatershed (Figure 1.1).

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Figure 1.1: Study area of Horsefly River watershed in British Columbia, Canada(Modified from Surveys & Mapping Branch, 1976).

The following questions were formulated to analyse the spatial variability of heavymetals in this river system:

1. Can the Black Creek mine be characterised in the sediment geochemistry ofBlack Creek and Horsefly River?

2. Can the metals be traced farther downstream along the Horsefly River?

3. What are the geochemical changes of the metals in the creek and downstreamriver?

This research was part of a joint study of effects from the abandoned Black Creekmine; Vogels (2013) explored the temporal variation of small-scale gold mining asrecorded in floodplain soils. Both studies were completed during the same timeperiod.

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1.2 Study Area

The Quesnel basin is located within the Central Interior region near the Cariboorange of the Columbia Mountains of British Columbia. Canada. Quesnel Lake isthe third deepest lake in North America at a depth of 512 m with a drainage basinof 5845 km2 and straddles three stratigraphic terranes on the Quesnel Plateau. TheHorsefly sub-basin (52 ◦19’ N/121 ◦1’ W) makes up 46% of the Quesnel watershedat 2983 km2 (Gilbert & Desloges, 2012).

The discharges of rivers throughout the Quesnel catchment are highly seasonalwith the mid-reaches of the Horsefly River reaching up to 124 m3/s in late May(Gilbert & Desloges, 2012). This river is the largest tributary of Quesnel Lakeat a length of 131 km and a Strahler stream order of six. Black Creek, whichdrains into the Horsefly River, is approximately 22 km upriver from the villageof Horsefly, 6.8 km in length and has a Strahler stream order of three (Holmes,2008).

1.2.1 Climate, Soil & Vegetation

The region around Horsefly River has a humid continental climate according to theKoppen climate system. Monthly mean temperatures and precipitation (Figure1.2) are recorded at the Horsefly Lake Gruhs Lake station (52.4 ◦ W/121.4 ◦ N;altitude: 777 m) since 1951. The annual precipitation, as recorded by the BCForest Service in Horsefly, is 564 mm.

The area of Black Creek is humid to subhumid, well drained and moderately torapidly pervious with gravelly, sandy- and loamy-skeletal morainal materials. Thedominant soil is eluviated dystric brunisol with some humo-ferric podzols (BritishColumbia Soil Survey, 1984). An immature soil, brunisols are less developed thanother soils due to long, cold winters, high altitudes, lack of moisture and youngparent materials. Dystric brunisols have a pH <5.5 and are similar to humo-ferricpodzols, which have a red horizon (Bf) of iron and aluminum and low organicaccumulation. In general, podzolic soils develop beneath coniferous forests fromintense leaching, have relatively high acidity and a strong profile development(Church & Ryder, 2010). Its vegetation zones are ESSFh, a wet subzone of theEngelmann spruce-subalpine fir zone and SBSb, a Douglas fir-white spruce subzoneof the sub boreal spruce zone (British Columbia Soil Survey, 1984).

On the other hand, along the Horsefly River the soil material is humid, moderatelywell drained and moderately pervious. Materials comprise of gravel, sand and loamassociated with morainal and fluvial systems and moderately decomposed sedge

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Figure 1.2: Mean monthly temperatues and precipitation of Horesfly, BritishColumbia.

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fen peat. The dominant soils are cumulic regosol and eluviated dystric brunisolswith some humo-ferric podzols. The area around Black Creek is characterised bya complex of regosols, organic soils and gleysols (British Columbia Soil Survey,1984). Regosols occur wherever local conditions have precluded soil development,i.e. young parent materials (sand dunes, river bars) or slow weathering and soil for-mation. Organic soils are composed mainly of organic matter. Found in wetlands,they are saturated for the majority of the year. Typical of poorly drained areasand on fine-grained parent materials, e.g. clayey till and glaciolacustrine sediment,gleysols are also saturated for extended periods and exhibit reducing conditions(Church & Ryder, 2010). Its vegetation zones are SBSb and ICHe, a dry subzoneof the interior cedar-hemlock zone (British Columbia Soil Survey, 1984).

Horsefly River is subjected to yearly floods and long periods of saturated soil(four to eight weeks). Shrub and sedge communities that can tolerate anaerobicconditions dominate these annually inundated areas. Black Creek and nearbyPatenaude Creek are major sources of sediment to the river floodplain (R. L. Case& Associates, 2000).

1.2.2 Geology & Placer Deposits

The study area lies to the west of the Cariboo Mountains, a part of the Ominecabelt in the Canadian Cordillera (Eyles & Kocsis, 1988). Most of the basement rockhere is from allochothonous terranes as a result of the Pacific Plate subductingunderneath the North America Plate during the past 1.8 billion years. Thesetectonic plates, along with Juan de Fuca/Explorer plate, control the province’stectonic, seismic and volcanic activity (Church & Ryder, 2010; Nelson & Colpron,2007).

In late Mesozoic and early Tertiary (∼70 to 35 Ma), extensive mountain buildinghad taken place. This was followed by erosion creating gentle slopes and broadvalleys and extrusion of basalt flows in the interior plateaus. The Pleistoceneglaciation helped shape the topography seen today, particularly in the mountains,with as many as 20 significant glacial episodes. The till deposited led to paraglacialsedimentation creating talus slopes, colluvial cones, alluvial fans and early flood-plains in the early Holocene (Church & Ryder, 2010).

Present-day geology of the Horsefly River catchment can be observed in Figure1.3. The occurrence of gold and other metals (e.g. copper, lead, zinc) found in thearea’s sediments is, according to data taken from the Cariboo mining district, mostlikely because of supergene leaching of gold dispersed within massive sulphides bydeep weathering followed by erosion (Ministry of Energy, Mines and Natural Gas,

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2013).

This supergene process that extensively alters country rock hosting sulphides isdepicted in Figure 1.4. As meteoric water percolates downward through hydrother-mal sulphide deposits, the metals oxidise forming various supergene or secondaryminerals – oxides/hydroxides, carbonates, sulphates, and native elements. Sul-phuric acid is a by-product of these oxidation reactions, thus dissociating andpromoting the dissolution of sulphide minerals, for example:

2Cu2S + 4H+ + 2SO42− + 5O2 = 4Cu2 + 4SO4

2− + 2H2O (1.1)

Once the meteoric water reaches the groundwater table, any dissolved metals andconstituents are diluted and often triggers sulphide precipitation by reversing reac-tions like the above. The reaction between sulphate solution and sulphide mineralsmay also cause precipitation. Since meteoric water is depleted of oxygen by thetime it reaches the water table, this area of supergene enrichment is also knownas the reducing zone.

When weathering and erosion progress, an encrusting mass called a gossan some-times accumulates at the surface. This is typically derived from the alteration ofpyrite creating an enrichment of insoluble yellow and red-coloured iron oxides andhydroxides (Nesse, 2000) and occasionally free gold (Maley, 2005).

The product of supergene enrichment, the metallic mineral deposits found inBritish Columbia, is the source for the placer deposits that form the foundationfor today’s mining activities. The mechanical and chemical concentration of heavyminerals from weathered rock, veins and pre-existing placer deposits forms vari-ous types of placers (Figure 1.5). This mixture of sand grains and metal flakesor nuggets is sorted and accumulated in sand or gravel bars along the course ofstreams and rivers (Maley, 2005; Marshak, 2005).

1.2.3 Black Creek Placers

These surficial and buried-channel placer deposits consist of layered, unconsoli-dated, reworked glaciofluvial gravel and sand that also contain abundant kyanite,schist fragments, garnet and quartz grains with a small amount of magnetite. Thedeposits rest on a bedrock of augite porphyry basalt flows, flow breccias and un-derlying bedded pyroxene-rich wackes and siltstones of the upper Triassic NicolaGroup (consists of basaltic volcanic rocks). Overlying these rocks are grey clays,which contain no gold; the gold is instead found in the lower, coarse gravel chan-

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Figure 1.3: Geology of central Quesnel Belt British Columbia, legend on next page(Modified from Bailey, 1987).

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Figure 1.4: Supergene enrichment process (Modified from Nesse, 2000).

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Figure 1.5: Placer deposits (Modified from Marshak, 2005).

nels of a complex network of crosscutting, filled river channels (Ministry of Energy,Mines and Natural Gas, 2013).

1.2.4 Fish & Wildlife

The Horsefly River is prime habitat for anadromous salmonids such as sockeye,Chinook, and Coho salmon and other fish species like rainbow trout, Dolly Vardenchar and mountain whitefish. It provides some of the most important sockeyeand rainbow trout spawning habitat in the Fraser River drainage area with thesalmon run a vital component of the valley’s ecosystem (BC Parks, 2013; TheLand Conservancy, 2013).

Historically, the Horsefly River supported a large sockeye escapement although re-cent years have seen steep declines, possibly due to unfavourable ocean conditions.The Horsefly river escapement is often more than the combined total of all otherQuesnel River tributaries (Albers, 2010). In 1993, 50% of the Fraser River sockeyerun was located in the Horsefly River. The river also produces an estimated 75%of the total rainbow trout for Quesnel Lake (The Land Conservancy, 2013).

The Horsefly River valley provides habitat for songbirds, waterfowl, winter birdsand moose in the winter. In autumn a high density of grizzly and black bears

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gather to feed on spawning sockeye. Species such as grey wolf, cougar, mule deer,beaver, muskrat, coyote, red fox, marten, ermine, long tailed weasel, mink, bobcatand lynx have also been observed in and around the region (The Land Conservancy,2013).

1.2.5 History & Landuse

Prior to the arrival of Euro-Canadian settlers and other inhabitants, the HoresflyRiver area was part of a north-south travel route used by the First Nations. In1859 at least four different prospecting groups discovered gold on this river, the firstsuch findings in the upper Cariboo (BC Parks, 2013; Horsefly Historical Society,1981).

Though prospectors continued farther north to find gold around Quesnel Riverand Barkerville, some miners stayed on to run small placer operations formingthe town of Horsefly. In 1885 there were reports of a group prospecting on BlackCreek and by 1887 a second gold rush began (Figure 1.6). Two hydraulic mineswere opened at this point, further increasing mining activity. The settlement ofBlack Creek was established (Horsefly Historical Society, 1981) as Mr Campbelldiscovered a placer deposit nearby in the late 1890s (Ministry of Energy, Minesand Natural Gas, 2013). By 1902 both hydraulic mines closed, but the Horseflycommunity continued to support themselves by mining small claims, ranching andtrapping (Horsefly Historical Society, 1981).

Figure 1.6: Panning for gold in the Horsefly River (Horsefly Historical Society,1981).

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Harold Armes and his family worked the Black Creek claim sporadically from the1920s to 1986. Acquired then by Mr L Shunter, it was worked for another twoyears before closing. In total 1928 grams of gold have been recorded, though theserecords are noted to be incomplete (Ministry of Energy, Mines and Natural Gas,2013).

Land has been cleared throughout the last century with the first machines used inthe 1950s. A log reload yard operated during the 1970s near an airstrip by BlackCreek and a small sawmill was active for a short time in the 1980s (R. L. Case &Associates, 2000).

Currently, land use activities include logging, agriculture, mining, urban and recre-ation (BC Parks, 2013; Holmes, 2008; Smith & Owens, 2010). Small to medium sizefarms and ranches for beef cattle and hay production are quite evident throughoutthe area. Two major forest licenses, the Provincial government, woodlot ownersand private landowners undertake the logging of the forest (Holmes, 2008).

The Land Conservancy (TLC) of British Columbia purchased riparian land alongsections of the Horsefly River around the Black Creek area between 1999 and2006. As one of TLC’s largest properties, the Horsefly River Riparian ConservationArea is almost 400 hectares along 12 km of river shoreline where one of the bestsockeye salmon spawning habitats in the world is located (The Land Conservancy,2013).

1.3 Mining

Mining is a method with which to extract minerals involving a sequential set ofprocesses. Using concentrations of trace metals in water is one method of findingore bodies as water, soils and sediments close to ore deposits are naturally enriched(Luoma & Rainbow, 2008).

Such activities promote the release of metals and expansion of disturbed areas overlarge regions, especially as there is often a low content of minerals in ore deposits.The waste includes excavated rocks, tailings, slags and residue. Oxidation anddissolution occurs when metals (mostly from sulphide ores) from the waste areexposed to the oxygen in air and water. These ores make up more than half ofthe major source of the most common trace metals, e.g. copper, lead and zinc.The oxidation of metal sulphides, mainly pyrite, could also generate highly acidicdischarges and lead to acid mine drainage:

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2FeS2(s) + 7O2(g) + 2H2O(l) = 2Fe2+(aq) + 4SO2−4 (aq) + 4H+ (1.2)

However, copper mines are the usual cause of acid mine drainage through theoxidation of chalcopyrite (CuFeS2) (Adriano, 2001; Faure, 1998; Rhyner et al. ,1995).

These mineral deposits are finite and often times economic limits are reachedbefore the ore runs out, thus resulting in the closure of the mine (Drever, 1997;Luoma & Rainbow, 2008). Ideally, the waste materials would then be returned tothe excavated region and the disturbed area rehabilitated, but this is not alwayspractical or possible (Adriano, 2001; Rhyner et al. , 1995).

Gold mining, as mentioned earlier, was and continues to be widespread in theCariboo region and has been a major economic activity in Canada since the 1800s(Azcue et al. , 1995). The Black Creek mine focused here is an example of a small-scale surface or open pit gold mine closely situated to a stream, as many historicallywere; an example of such mine is shown in Figure 1.7 (Hale, 1994).

Figure 1.7: Stouts Gulch mine adjacent to Lowhee Creek in Cariboo region ofBritish Columbia. This is an example of what Black Creek mine might havelooked like with hydraulic operations (Eyles & Kocsis, 1988).

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1.3.1 Quesnel Case Studies

A few pilot studies were conducted in the Quesnel watershed in British Columbia.Smith & Owens (2010) collected fine-grained suspended sediment from streamsdraining different land use activities. Their results suggested mining and logginghave greater influence on metals and nutrients as opposed to agriculture. At streamsites draining a mining area, concentrations of arsenic, copper and selenium wereexceptionally elevated.

The thesis of Karimlou (2011) and van Lipzig (2011) followed up on these con-clusions and determined that mining activities are influencing the fine sedimentgeochemistry of the Quesnel catchment, though whether its major or minor de-pends on the type of mine, methods used and the containment of the mine’stailings. Hazeltine Creek, which empties into Quesnel Lake and receives drainagefrom an active open-pit copper-gold mine, was of particular focus. Geochemicalresults pointed to enrichments of arsenic, copper, manganese. These enrichmentshowever are mostly induced by the increased exposed rock to weathering as a resultof mining rather than from direct anthropogenic inputs (van Lipzig, 2011).

1.3.2 Wales Case Study

For comparison, mining activities and waste was quite concentrated in many re-gions around Europe such as the United Kingdom. Despite the decline in metalmining in the past century, heavy metal contamination still persists in the coun-try’s river channel and floodplain sediments. Byrne, Reid and Wood’s (2010) studyon a lead and zinc mine in central Wales looked at metal concentrations and geo-chemical phases of riverbed sediments. Most heavy metals were found to be in themost mobile easily exchangeable and carbonate-bound geochemical phase. Thiswould pose as a secondary diffuse source of pollution, especially as the proportionof readily extractable zinc and cadmium gradually increases downstream. Concen-trations of all metals did decrease sharply downstream of the inactive mine.

1.4 Description of Heavy Metals

1.4.1 Arsenic

Arsenic is a semi-metal, ubiquitous in nature, a toxic non-essential element andgeochemically similar to phosphorus. As(III) and As(V) are the primary species

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of As in soils and natural waters with As(III) the more soluble, mobile and toxicof the two and As(V) the most common in water. Primarily bound to sedimentsin aquatic systems, the formation of As(V) is favoured under conditions of highlydissolved oxygen, alkaline pH, high redox and reduced organic matter content.The main As forms in river sediments are: Al arsenate, Fe arsenate, Ca arsenateand Fe-occluded As (Adriano, 2001; Chunguo & Zihui, 1988; Drever, 1997; van derPerk, 2006).

Arsenic is known to have a high affinity for oxide surfaces, e.g. Fe(III), Al(III),Mn(III/IV), which are a significant As sink for in aquatic systems. It can alsoadsorb to humic substances and clay minerals. Oxidation of As(III) to As(V) isattributed to As(III) reacting with Mn oxides (Adriano, 2001; Bissen & Frimmel,2004; Chiu & Hering, 2000; Mok & Wai, 1994; van der Perk, 2006).

As a natural constituent in copper, gold, lead and zinc ores, arsenic is released intothe environment through mining and smelting operations (Adriano, 2001; van derPerk, 2006).

1.4.2 Cadmium

Cadmium is a naturally occurring metal, a highly toxic non-essential element andgeochemically similar to zinc, though less abundant. The dominant stable speciesis Cd(II). The most common compound is CdS, though it also forms hydrox-ides, complex ions with ammonia and cyanide, complex organic amines, sulphurcomplexes, chloro-complexes and chelates. Its ions form insoluble, usually hy-drated, white compounds with carbonates, arsenates, phosphates, oxalates andferrocyanides.

Complexed by natural organic matter, humic substances are considered to be amajor Cd adsorbent in oxic sediments. It is also potentially affected by adsorptionon Fe and Mn oxides and calcite. Cd is linked to copper, lead and zinc and acommercial by-product of the zinc industry.

Though the principal anthropogenic source is from the burning of fossil fuels andincineration of municipal waste materials, it may also be released from copper,lead or zinc smelters (Adriano, 2001; Drever, 1997; Fu et al. , 1992; van der Perk,2006).

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1.4.3 Copper

Copper is an important metal for society and an essential micronutrient for plantsand animals. It occurs either as a free metal or in the I and II oxidation states.Cu(II) is isomorphous with Fe(II), Mg(II) and Zn(II). Common minerals arecuprite, malachite, azurite, chalcopyrite and bornite while also forming sulphides,sulphates, sulfosalts, carbonates and native metal.

Due to strong sorbtions and complexations by organic matter, Fe and Mn oxidesand clay minerals, Cu is one of the least mobile trace metals. It is commonlyassociated with cadmium, lead and zinc with metal affinity generally followingthe order: Pb >Cu >Zn = Cd. Thus Cu(II) is the most strongly adsorbed of alltransition metals, besides Pb(II), on oxides and oxyhydroxides, and is also the mosttoxic form to aquatic life. The bioavailability of Cu is determined by the presenceof Fe and Mn oxides and dissolved organic carbon in aerobic environments andsulphides in anaerobic systems.

The most economically important Cu ores are sulphides, oxides and carbonates.As a result of mining and smelting, soil and water pollution occurs (Adriano, 2001;Drever, 1997; van der Perk, 2006).

1.4.4 Selenium

Selenium, an essential nutrient for animals, exists in four oxidation states: VI(selenate), IV (selenite), 0 (elemental Se), and –II (selenite). Though officiallyclassified as a metalloid, i.e. has properties of both a metal and a non-metal, it iscommonly associated with heavy metal sulphides and can substitute for sulphur.At high Se concentrations, interactions with arsenic, cadmium and silver have beenobserved.

Selenate is dominant in oxidizing conditions, similar to sulphate, and a more toxicsource of Se than selenite at lower S concentrations. There have been instanceswhere selenate has absorbed onto Fe oxides in the laboratory, most likely in theabsence of sulphate. At intermediate conditions, selenite occurs (analogous to sul-phite) and is the most bioavailable form of dissolved inorganic Se. Under reducingconditions, elemental Se and hydrogen Se (analogous to hydrogen sulphides) ispresent.

The usual source of Se in nature are shales that naturally contain high Se levels. Sealso accumulates over time from leachates or drainage waters in low-lying areas orregions with clay pans. Anthropogenic sources include fertilizers and the burningof fossil fuels (Adriano, 2001; Drever, 1997; Luoma & Rainbow, 2008).

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1.4.5 Zinc

Zinc is an essential trace nutrient for plants and animals with a natural oxidationstate of II. As it can react either as an acid or base, Zn forms a variety of salts -chlorates, chlorides, sulphates and nitrates that are readily soluble in water andoxides, carbonates, phosphates, silicates and sulphides that are relatively insolublein water.

Zinc has an affinity for Fe and Mn oxides, less so for organic matter and is com-monly associated with cadmium, copper and lead. Most Zn production comes fromsulphide ores; consequently mining and smelting can lead to severe zinc pollution(Adriano, 2001; Drever, 1997; van der Perk, 2006).

1.5 Metals in Aquatic Envrionments

Surface waters like rivers and streams are fed by the inflow of rising groundwater,occasional overland flow or through flow from surrounding uplands and precipita-tion. Rivers and streams also frequently tend to receive metal-containing wastesfrom mining sites. Water is then removed by discharge, infiltration and evapora-tion (van der Perk, 2006).

The hyporheic zone (Figure 1.8) consists of porous, hydraulically conductive, clas-tic sediments and organic matter. The composition of these bed sediments is theproduct of weathering, erosion, transport and deposition. They either originateupstream or are derived from local rocks. These sediments retain, store or releasesignificant amounts of nutrients and heavy metals. Through hydrological processesand geochemical and physical mobilisation, the metals are transported, depositedand remobilised thereby extending their dispersal (Hale, 1994; Luoma & Rainbow,2008; van der Perk, 2006).

Generally, the redox potential is higher in surface water than in groundwater be-cause of the presence of relatively high concentrations of dissolved oxygen. Surfacewater normally has a pH between 6.5 and 8.5 (Hale, 1994; van der Perk, 2006). AtpH near neutral, i.e. most natural freshwater bodies, the partitioning of metals be-tween solution and solid phases strongly favours certain materials. Subsequently,sediments and suspended particulate material form the largest repository of metalsin a water body (Luoma & Rainbow, 2008).

Under all conditions, metal ions associate with the surface of particles that havehigh surface area and a high capacity to exchange with cations (positively chargedions). The associations that can be formed depend on the reducing and oxidising

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Figure 1.8: The hyporheic zone of a stream (Winter et al. , 1998).

conditions; for instance, under oxic conditions metals are more easily retainedby soils and sediments and the precipitation of oxides are dominant (Luoma &Rainbow, 2008).

Metals have a tendency to separate between solid (particulates) and aqueous (dis-solved) phases (Figure 1.9). Several studies report that roughly 90% of metals aretransported in particulate form, especially the fine (<63 /mum) fraction. Thispartitioning is largely determined by redox potential and pH, which are inverselyrelated because of H+ ion formation under oxidised conditions, in addition to thenature of the contaminant source (Luoma & Rainbow, 2008; Smith & Owens, 2010;van der Perk, 2006).

Concentrations of metals measured in this study are in the solid phase, which aretypically higher than concentrations in the aqueous phase. The reactivity of metalsis largely determined by the specific surface area. Coarse materials with a smallspecific surface area are much less reactive than fine or colloidal materials with alarger area. The silt and clay fractions, which contain a high amount of organicmatter, precipitates and clays, are the major carriers of metals (Hale, 1994; Luoma& Rainbow, 2008; van der Perk, 2006).

1.6 Geochemical Phases of Metals

Even if inputs of metals cease, the sediments will still preserve a historical recordand continue to remain a source to the water column and organisms. Heavy metalscan bind to the surfaces of many solid compounds, e.g. clay minerals, carbonates,Fe/Mn oxides, organic matter and sulphides. These bonds between metals and lig-ands control the potential mobility of metals and can change with altered physical

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Figure 1.9: Internal processes that affect the formation of particulate metals inthe sediments (Modified from Luoma & Rainbow, 2008).

and/or chemical conditions (Byrne et al. , 2010; Calmano et al. , 1993; Hale, 1994;Luoma & Rainbow, 2008; van der Perk, 2006). The mixture of metals and com-plexing agents present, pH, ionic strength and major ion composition determinesthose bonds (Morel, 1983).

Metal oxides, e.g. Fe and Mn, have essentially an infinite source of exchange-able ligands and the ability to simultaneously adsorb metals and ligands. Thisbehaviour is linked to the concentration of background electrolytes and increaseswith pH as a result of the decreasing competition with H+ for surface ligands.Adsorption on oxides can also take place against an electrostatic repulsion (Morel,1983). Fe and Mn oxides have a strong affinity for metals because of their highadsorption capacities and are typically present as fine grains with large surfaceareas (Drever, 1997; Hale, 1994; Luoma & Rainbow, 2008).

Organic matter also has a high attraction for metals and contributes to streamsediments via detritus, sedimentation, solution transport and trapping, and in situbiological activity (Drever, 1997; Hale, 1994; Luoma & Rainbow, 2008). Under

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oxidising conditions, metals bind to organic matter and sulphides can be easilyreleased (Filgueiras et al. , 2002).

When there are low amounts of Fe and Mn oxides and organic matter, metalscan strongly complex to carbonates. However, these complexes are loosely bound,easily susceptible to changes in environmental conditions (Filgueiras et al. , 2002)and most likely insignificant to metal adsorption (Morel, 1983).

Metals can also be incorporated into sulphides by adsorption, precipitation orlattice exchange, though studies are difficult due to surface oxidation. The limitedstudies completed do suggest that adsorption is dominated by surface hydroxyl (-OH) groups similar to that of metal oxides as opposed to surface sulfhydryl (-SH)groups (Morel, 1983).

Insoluble minerals formed under anoxic conditions dominate ores. These metalsare assumed to have limited bioavailability, but their speciation is influenced bydiagenesis in an aqueous environment (Luoma & Rainbow, 2008). Frequentlyafter anthropogenic activities like mining, metals exist as exchangeable ions andcarbonate-bound metals, which can easily interact with plants and animals (Jain,2004), but the metals incorporated into a sediment’s crystal lattice are consideredunavailable to biota (Byrne et al. , 2010; Morillo et al. , 2002).

Either a single reagent could be applied to extract elements from certain phases, apartial extraction, or a series of reagents of increasing strength can be applied, i.e.a sequential extraction procedure. These extractions were originally designed bysoil scientists and have been in use for a long time as it helps determine the phasesand speciation of metals. Tessier, Campbell and Bisson’s (1979) highly cited pa-per outlines steps to differentiate the tendencies of metal forms under differentconditions (Hale, 1994; Luoma & Rainbow, 2008). Another common scheme is thestandardised modified BCR (European Community Bureau of Reference) proce-dure (Rauret et al. , 1999) that has reference materials and is applied successfullyto a variety of matrices (Hass & Fine, 2010).

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Chapter 2

Methods

2.1 Sampling Locations

The Quesnel River Research Centre (QRRC) of University of Northern BritishColumbia (UNBC), located in Likely, was utilized as a base to prepare collectedsamples for laboratory analysis.

13 sampling sites were chosen based on location and accessibility along the BlackCreek and Horsefly River, as seen in Figure 2.1. Pictures of Black Creek (Figure2.2) are of sites BC 2 and BC 3, respectively, whereas Figure 2.3 is along theHorsefly River at HR 5.

2.2 Sampling Methods

At each site resuspended or riverbed sediment samples were collected, describedin Table 2.1, as well as source rock material from the abandoned mine along BlackCreek. Temperature, pH and electrical conductivity (EC) were also measured atall Horsefly River sites and three of the five Black Creek sites.

2.2.1 Resuspended Sediment

Two different methods were used in order to resuspend and collect a representativesediment sample. Only two sites along the Horsefly River were chosen to use acontinuous flow centrifuge due to accessibility and river depth. The centrifuge

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Figure 2.1: Sample locations, refer to Table 2.1 for more details on each location(Modified from Figure 1.1).

Figure 2.2: Abandoned open pit of Black Creek mine (left); remnants of woodensluice boxes in Black Creek (right).

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Figure 2.3: Horsefly River downstream of Black Creek.

Table 2.1: Description of samples.

Location Sample Material MethodBlack Creek (BC) BC 1 BC 1.1 Bed Sediment Trowel

BC 2 BC 2.1 Source TrowelBC 2.2BC 2.3BC 2.4BC 2.5BC 2.6

BC 3 BC 3.1 Bed Sediment TrowelBC 4 BC 4.1 Bed Sediment TrowelBC 5 BC 5.1 Bed Sediment Trowel

BC 5.2 Resuspended Sediment BucketHorsefly River (HR) HR 1 HR 1.1 Resuspended Sediment Bucket

HR 1.2 Continuous CentrifugeHR 2 HR 2.1 Resuspended Sediment BucketHR 3 HR 3.1 Resuspended Sediment BucketHR 4 HR 4.1 Resuspended Sediment BucketHR 5 HR 5.1 Resuspended Sediment BucketHR 6 HR 6.1 Resuspended Sediment BucketHR 7 HR 7.1 Resuspended Sediment BucketHR 8 HR 8.1 Resuspended Sediment Bucket

HR 8.2 Continuous Centrifuge

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(M512 manual cleaning centrifuge, US Centrifuge Systems) was powered by agenerator and ran for approximately 20 minutes as sediment was kicked up fromthe channel bed creating a sediment plume in front of the pump. Fine sedimentwas scrapped out of a bucket within the centrifuge and collected into vials to beair-dried.

The second resuspension method was used at all Horsefly River sites and one BlackCreek site. Three accessible spots were chosen at each site where the water depthwas low enough as to not spill over the sides of the bucket. Suction was createdwith the channel bed and the sediment stirred up with a trowel until there was asufficient amount of resuspended material in the water. Ten seconds passed beforecollecting water from the first ten cm within the bucket in order to allow for largerparticles to fall out leaving more fine sediments. Once collected into five gallon(∼19 L) containers, water was then suctioned off after waiting an adequate amountof time for any sediment suspended to settle to the bottom. The remaining waterwith sediment was poured into small vials to be centrifuged (Damon/IEC EXDCentrifuge @ 40000 rpm), decanted and then air-dried (Figure 2.4).

Figure 2.4: Collecting resuspended sediment at HR 6 (left); centrifuging, decant-ing, and air-drying of sediment samples (right).

2.2.2 Source Material & Bed Sediment

Lastly, source rock material from the abandoned mine and channel bed sedimentswere collected in plastic bags along the Black Creek using a trowel and then air-dried.

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2.2.3 Sample Preparation

Once all sediments were completely dried, they were weighed and subsamples fromthe resuspended bucket sites were thoroughly mixed together in order to create arepresentative sample. Next these sediments were ground with a mortar and pestleto break up aggregates and sieved to collect less than 63 µm particles (Figure 2.5).The fine sediment sample was then weighed and stored in plastic bags to be furthersubdivided.

Figure 2.5: Grinding of fine sediments with mortar and pestle.

Vogels (2013) had completed a similar pilot study on the Black Creek mine withthe objective of investigating the temporal variation of metal concentrations infloodplain soils. Collection and preparation of sediment cores taken from flood-plains along the Horsefly River are described in detail in her study.

2.3 Organic Matter

The amount of organic matter was estimated using the loss on ignition method(Ball, 1964). Dry sediment was ashed at 500 ◦C for about an hour (Figure 2.6)and the difference weighed:

OMcontent(%) =moven−dried −mair−dried

mair−dried

∗ 100% (2.1)

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Figure 2.6: Loss of ignition method to measure percentage of organic matter.

2.4 Particle Size

Particle size distribution was measured with a Malvern Mastersizer 3000 at UNBC.Samples were first prepared by burning off organic matter via hydrogen peroxidein vials containing 1.5 to 2 g of sediment (Figure 2.7). Five ml of deionizedwater was then added and allowed to soak overnight. To agitate the particles, thesamples were sonicated for one minute at about five Watt rms (Fisher Sonicator)and approximately two to three ml were directly sub-sampled into a pipette andentered into the Mastersizer 3000 for particle size analysis.

Figure 2.7: Applying hydrogen peroxide to burn off organic matter before particlesize analysis.

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2.5 Geochemical Analysis

Geochemical analysis was performed using aqua regia digestion following the ISO11466 protocol and the modified BCR 3-step sequential extraction (Figure 2.8)(Rauret et al. , 1999). In addition, the residue from the third step of sequen-tial extraction was digested in aqua regia. Extractions were then measured usingICP-OES (inductively coupled plasma optical emission spectrometry) at UtrechtUniversity in the Netherlands.

Figure 2.8: Modified BCR’s three step sequential extraction.

To obtain background concentrations, data was obtained from a sediment core(Figure 2.9) upstream of Black Creek from Vogels’ pilot study (2013). Sampleswere dated using the Pb-210 method at University of Plymouth in the United King-dom and metal concentrations measured by ICP-MS (inductively coupled plasmamass spectrometry) from aqua regia digestion at the ALS (Australian LaboratoryServices) Group in Vancouver, Canada.

Figure 2.9: Sediment core from Horsefly River floodplain (Vogels, 2013).

As a check to compare geochemical results between the laboratories in Utrecht andVancouver, five bed and resuspended sediment samples were randomly selected andsent to the ALS Group for analysis.

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2.5.1 Aqua Regia Digestion

Aqua regia digestion is a common method to determine amounts of elements insoil and sediment. Despite the original description that “elements, extractable inaqua regia cannot be described as ‘totals. . . ’” results are still referred to as “totalcontents” mainly in comparison to other extraction procedures using weaker acids.There are techniques that do result in a true total of element concentrations,such as XRF (X-ray fluorescence) and INAA (instrumental neutron activationanalysis) or total dissolution using HF and HCl. Some studies still knowingly usethe “pseudototal contents” of aqua regia digestion in their analysis and refer to theresults as “total contents” (Taraskevicius et al. , 2013). This will also be the casein this thesis and any reference made to “total” concentrations is in knowledgethat these concentrations are in actuality the “pseudototal.”

2.5.2 Sequential Extraction

As described earlier, sequential extraction is a method to apply a succession ofreagents to determine metal associations. In this study, the modified BCR protocolis utilised, as it is standardised and sufficiently repeated and reproducible to beapplicable to metals.

The four steps are delineated in numerous studies (Basta et al. , 2005; Filgueiraset al. , 2002; Hullebusch et al. , 2005; Kartel et al. , 2006; Nyamangara, 1998) andrepresent the following fractions (Byrne et al. , 2010; Hass & Fine, 2010):

1. acid-soluble, exchangeable and bound to carbonates

2. reducible, bound to iron and manganese oxides

3. oxidisable, bound to organic and sulphide compounds

4. residual

The total amount of metal extracted, i.e. the sum of the four steps, was comparedwith that obtained by aqua regia digestion (Rauret et al. , 1999).

2.6 Statistical Analysis

Aluminum can be used as a normalising constituent for particle size if a directlinear relationship is established. Heavy metal concentrations are partly deter-mined by a sediment’s capacity to adsorb organic matter and clay, varying in

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concentrations as the amount of clay and organic matter varies. Since aluminumis incorporated by clay, it can be used as a normalising constituent for clay contentif a direct linear relationship is established (Loring, 1991; Luoma & Rainbow, 2008;van der Perk, 2006). Therefore linear regression is used to analyse the relationshipbetween Al concentrations and particle size and subsequently with heavy metalconcentrations.

With each linear regression analysis, the R2 and p-value are calculated. R2 is thecoefficient of determination and measures the strength of the regression betweentwo variables. Values range between zero and one with one representing a perfectcorrelation. The p-value is a measure of the coefficient’s significance in the linearregression. As 95% confidence interval is used, anything less than 0.05 is consideredsignificant.

The correlation coefficient, r, is calculated to determine the closeness of metalconcentrations between the results of the aqua regia digestion technique betweenthe laboratories in Vancouver and Utrecht (Hale, 1994).

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Chapter 3

Results & Discussion

3.1 pH and EC

The pH of Black Creek and Horsefly River at sites where sediment samples werecollected are within the normal range of natural waters (Figure 3.1). EC mea-surements were higher in the Black Creek and increased downstream towards theHorsefly River. The Horsefly River sites had a lower EC, but also increased down-river. EC values are within reason of measurements taken in natural waters.

Figure 3.1: pH and EC of Black Creek and Horsefly River sites.

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3.2 Particle Size Distribution

There is a positive correlation between the amount of Al and the size of the clayfraction, e.g. particle sizes below two µm (Figure 3.2). This relationship allowsfor the use of Al as a proxy for grain size as to remove the effect of particle sizeon heavy metal concentrations.

Figure 3.2: Al concentrations [%] plotted against the percentage of particles be-tween 2 µm from all samples.

Table 3.1: Linear regression analysis of Al [%] vs particles below 2 µm [%].

Linear regression y = 0.848x + 16.084R2 0.593p-value 0.00000416Standard error 0.897# of samples 25

The amount of clay in the collected samples showed higher fractions along theBlack Creek compared to the Horsefly River (Figure 3.3). Sediment collected fromthe abandoned hydraulic pit at Black Creek Mine showed clay fractions range from8.2% to 18.4% of the samples, whereas samples from along Black Creek had moreconsistent amounts from 10.6% to 16.4%. Horsefly River samples showed fractionsfrom 4.4% to 9.2% with one sample that contained 13.4% clay.

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Figure 3.3: Percentage of particles below 2 µm of Black Creek and Horsefly Riversites (D = duplicate).

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3.3 Organic matter content

Organic matter ranges from 0.82% to 1.22% (Figure 3.4) of the sieved sedimentsample. These low values could be possibly attributed to the low organic mattercontent of the region’s soils. However, the floodplain soils analysed in Vogels’study (2013) range from 2.95% to 13.08%.

Figure 3.4: Percentage of organic matter.

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3.4 Comparison Studies

3.4.1 Collection Methods

Two collection methods for resuspended sediment were completed and compared;Table 3.2 shows these concentrations. The sampling technique shows good cor-relation with each other with the exception of zinc. Subsequently, sites HR 1.2and 8.2 will not be taken into consideration when interpreting results for zincconcentrations, though they will still be included for continuity.

Table 3.2: Metal concentrations [mg/kg] between the sample collection methodsfor resuspended sediment.

Element Site Bucket CentrifugeAl [%] HR 1 1.561 1.452

HR 8 2.343 1.952As HR 1 7.810 5.910

HR 8 17.220 10.470Cd HR 1 0.690 0.620

HR 8 0.650 0.500Cu HR 1 37.720 35.880

HR 8 76.690 40.540Se HR 1 0.944 0.495

HR 8 1.910 1.252Zn HR 1 88.740 79.490

HR 8 105.610 77.340

3.4.2 Laboratory Analysis

As background concentrations of the sediment core measured in Vancouver wereused to compare totals of sediments along Black Creek and Horsefly River analysedin Utrecht, the correlation coefficients are calculated and shown in Table 3.3. Cdand Zn are not as strongly correlated as As, Cu and Se, but all have acceptablecorrelations.

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Table 3.3: Concentrations [mg/kg] and correlation coefficient, r, between aquaregia digestion results from laboratories in Vancouver, Canada and Utrecht, theNetherlands.

Element Sample Utrecht VancouverAl [%] BC 1.1 2.804 1.630

BC 2.1 3.079 1.910BC 3.1 2.404 1.430BC 5.2 3.121 1.980

r = 0.943 HR 7.1 1.932 1.360As BC 1.1 14.190 12.300

BC 2.1 50.670 51.400BC 3.1 26.250 25.700BC 5.2 22.620 21.200

r = 0.998 HR 7.1 5.790 6.600Cd BC 1.1 0.380 0.300

BC 2.1 0.440 0.350BC 3.1 0.320 0.270BC 5.2 0.450 0.470

r = 0.937 HR 7.1 0.550 0.550Cu BC 1.1 65.620 53.800

BC 2.1 83.030 72.200BC 3.1 56.440 50.700BC 5.2 77.690 68.100

r = 0.964 HR 7.1 47.250 48.100Se BC 1.1 0.581 1.000

BC 2.1 0.380 1.100BC 3.1 0.510 1.000BC 5.2 1.870 3.000

r = 0.983 HR 7.1 0.917 1.800Zn BC 1.1 82.190 68.000

BC 2.1 78.330 70.000BC 3.1 61.800 53.000BC 5.2 94.140 83.000

r = 0.877 HR 7.1 86.640 91.000

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3.5 Total Metal Concentrations & Metal Speciation

3.5.1 Aluminum

The Black Creek samples had higher concentrations of aluminum and minimalvariation (Figure 3.5). Concentrations were also higher than the background con-centrations. Horsefly River samples had lower Al concentrations that generally in-creased downriver. At HR 2, HR 5 and HR 8, there were larger differences betweenAl concentrations of the previous sample sites, in addition to being higher thanbackground concentrations. As the amount of Al and clay are directly related, Alconcentrations generally correspond to the percentage of clay in the samples.

The majority of Al in Figure 3.6 was found in the Fe/Mn oxide step, with aportion also found with sulphides and organics. There was a higher percentageof Al with Fe/Mn oxides in the Black Creek mine samples compared to the restof the samples. This confirms the fact that Al is found in many compounds, butforms most commonly as an oxide.

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Figure 3.5: Al concentrations [%] from aqua regia digestion and sequential extrac-tion procedure of Black Creek and Horsefly River sites. Background concentrationsfrom the sediment core are plotted as a reference value.

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Figure 3.6: Percentage of Al measured in the first three steps (exchange-able/carbonate, Fe/Mn oxides, sulphide/organic) of the sequential extraction pro-cedure.

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3.5.2 Arsenic

Arsenic concentrations have an overall positive relationship with Al concentrationsin the linear regression shown in Figure 3.7. However, when broken down thereis no relationship between As and Al in the Black Creek sediments and a lesssignificant relationship in the Horsefly River sediments.

Table 3.4: Linear regression analysis of As [mg/kg] vs Al [%].

Linear regression y = 2.492 x - 39.793R2 0.518p-value 0.00011Standard error 3.636# of samples 23

Black Creek R2 0.243p-value 0.399

Horsefly River R2 0.348p-value 0.0560

Source Material R2 0.671p-value 0.0242

Ratios of metals, like As and the other heavy metals, and Al will be used to inter-pret total concentrations as to diminish the effects of particle sizes. In instanceswhere there no relationship is found between the metal and Al, the observed con-centrations of the metal will also be considered (Appendix C).

Arsenic in the Black Creek and Horsefly River samples, shown in Figure 3.8, weresimilar to background levels with the major exception of site BC 2 where samplesfrom the mine were collected. Some of these amounts are more than triple ofthe background and likely from high exposure and weathering rates of the aban-doned mine pit. Once entering Black Creek, As had an immediate local effect onconcentrations seen in BC 3.1, but no lasting effect once it entered the HorseflyRiver.

Historically, higher As levels had been found along the Horsefly River after BlackCreek in the sediment cores of Vogels’ study (2013), but had decreased with timedue to the lack of intensive gold mining.

Arsenic concentrations determined from sequential extraction occurred mostly inthe Black Creek samples, especially from the mine, as well as sites HR 5 and HR 8(Appendix B). All As measured in the three steps were found in the Fe/Mn oxidecomponent of the procedure. Since As strongly binds to Al, Fe and Fe oxides, this

40

was expected. It is probably in oxidation state V as this is more commonly foundin waters and in conditions of highly dissolved oxygen, alkaline pH and low organicmatter. Any As(III) would have also likely reacted with Mn oxides to As(V).

Figure 3.7: As concentrations [mg/kg] plotted against Al concentrations [%] forall sites.

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Figure 3.8: As concentrations [mg/kg] normalised against Al concentrations [%]from aqua regia digestion and sequential extracture procedure. Background con-centrations from the sediment core are plotted as a reference value.

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3.5.3 Cadmium

There is an overall negative correlation between Cd and Al concentrations, as seenin Figure 3.9. Upon separating out the Horsefly River, Black Creek and minesamples, only the Horsefly River sediments have a significant correlation with Al.Both the Black Creek and mine sediments have no relationship with Al. Of noteis that were was also poor linear correlation between Cd and Al in Vogels’ study(2013).

Table 3.5: Linear regression analysis of Cd [mg/kg] vs Al [%].

Linear regression y = 0.0169 x + 0.0967R2 0.184p-value 0.0413Standard error 0.0414# of samples 23




Cadmium levels were lower in the Black Creek than the Horsefly River in additionto the background levels, seen in Figure 3.10. The same also goes for the ob-served concentrations as shown in Appendix C. Horsefly River samples had higheramounts than the background. It can be concluded then that the Black Creek isnot a significant source for Cd.

The total concentrations from the aqua regia digestion could not be compared tothe sequential extraction due to laboratory contamination during the latter. It ispossible that Cd had similar speciation to Cu and Zn as it is commonly associatedwith these metals.

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Figure 3.9: Cd concentrations [mg/kg] plotted against Al concentrations [%] forall sites.

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Figure 3.10: Cd concentrations [mg/kg] normalised against Al concentrations [%]from aqua regia digestion and sequential extracture procedure. Background con-centrations from the sediment core are plotted as a reference value.

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3.5.4 Copper

Figure 3.11 shows that Cu and Al concentrations have an overall positive correla-tion with each other, though the Black Creek samples by themselves again showno relationship with Al.

Table 3.6: Linear regression analysis of Cu [mg/kg] vs Al [%].

Linear regression y = 2.690 x - 2.867R2 0.733p-value 0.000000187Standard error 3.297# of samples 23




Copper levels were generally similar for both Black Creek and Horsefly River andbelow background levels, with the exception of samples HR 5.1 and HR 8.1 (Figure3.12). Source material from the mine (BC 2) was slightly higher in Cu comparedto the rest of the Black Creek samples. In the observed concentrations (AppendixC), Cu at in the Black Creek sites had levels more similar to the backgroundconcentrations.

In Figure 3.13, the Black Creek mine samples showed a tendency for Cu toonly be in the Fe/Mn oxide component, whereas the Black Creek and HorseflyRiver samples showed portions also found in the exchangeable/carbonate and sul-phide/organic components.

Though Cu has the tendency to adsorb to Fe/Mn oxides, it also is associated withorganic matter and clay minerals. As Cu oxidises due to exposure and weatheringat the mine and is released into Black Creek, its speciation appears to change toalso adsorb to the less mobile sulphides and organics.

Cu(II) is one of the most strongly adsorbed metals and would quickly bind toany solid surface available. Thus this apparent alteration in speciation could bebecause of higher amounts of solids like sulphides and carbonates as compared tooxides that are available for metal binding in the Horsefly River.

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Figure 3.11: Cu concentrations [mg/kg] plotted against Al concentrations [%] forall sites.

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Figure 3.12: Cu concentrations [mg/kg] normalised against Al concentrations [%]from aqua regia digestion and sequential extracture procedure. Background con-centrations from the sediment core are plotted as a reference value.

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Figure 3.13: Percentage of Cu measured in the first three steps (exchange-able/carbonate, Fe/Mn oxides, sulphide/organic) of the sequential extraction pro-cedure.

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3.5.5 Selenium

When separating the Horsefly River and Black Creek samples, there is a goodcorrelation between Se and Al concentrations of Horsefly River compared to anoverall negative correlation among all the samples, as shown in Figure 3.14. Thereis no relationship between Se and Al of the mine and Black Creek samples, whichis similar to the linear regression analysis of Cd (Figure 3.9).

Table 3.7: Linear regression analysis of Se [mg/kg] vs Al [%].

Linear regression y = -0.0171 x + 1.321R2 0.0156p-value 0.570Standard error 0.144# of samples 23




Figure 3.15 as well as the observed concentrations in Appendix C shows overallthat there was a large variation of Se for all the samples along the Black Creek andHorsefly River. The highest Se amounts were from samples HR 5.1 from aqua regiadigestion and HR 8.2 from sequential extraction. Sites along the Horsefly Riverwere closer to background levels whereas the Black Creek samples were generallylower.

No Se was detected in samples BC 1.1D or BC 2.6 using aqua regia digestionor sequential extraction. The high Se concentration of HR 8.2 from sequentialextraction is most likely because of overestimation of each step when analysed bythe ICP-OES.

The difference in amounts of Se could be a result of sample collection methods, asSe was higher from resuspended sediment samples (BC 5.2 and all HR) comparedto samples of bed sediments and source material from the mine (BC 1.1 to BC5.1).

HR 5 and HR 8 had higher Se compared to the previous sites upriver (HR 4 andHR 7) indicating that there are other sources of Se entering the Horsefly River.BC 5.2, HR 2.1 and HR 3.1 all had similar Se; these sites represent the entrance

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of Black Creek into the Horsefly River. These levels were not higher than HR 1.1(upstream Horsefly River), therefore there is an insignificant amount of Se enteringin from Black Creek.

In the study of Vogels (2013), Se had been found to be gradually accumulatingover time along the Horsefly River. This accumulation is to be expected as it isoften building up in low-lying areas or where there are clay pans from leachatesor drainage waters. Any weathering could then continue to increase Se levels.Consequently, these insignificant amounts of Se could be still contributing to over-all amounts. These increasing Se concentrations observed in the sediment cores,Vogels attributes to other uninvestigated mining sites further upstream HorseflyRiver.

Most Se was measured in the Horsefly River samples and all were found in thesulphide/organic component of sequential extraction (Appendix B). This can beattributed to the fact that Se can substitute for S and has an affinity for heavymetal sulphides.

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Figure 3.14: Se concentrations [mg/kg] plotted against Al concentrations [%] forall sites.

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Figure 3.15: Se concentrations [mg/kg] normalised against Al concentrations [%]from aqua regia digestion and sequential extracture procedure. Background con-centrations from the sediment core are plotted as a reference value.

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3.5.6 Zinc

By separating out samples by locations, the seemingly non-existent relationshipbetween Zn and Al gives way to positive correlations between all samples and Al inFigure 3.16. The Black Creek sediments in this case seem to have a much betterlinear relationship than between the other metals and Al, perhaps due to Zn’sability to react either as an acid or a base and form a large variation of salts.

Table 3.8: Linear regression analysis of Zn [mg/kg] vs Al [%].

Linear regression y = -0.7008 x + 108.032R2 0.0294p-value 0.434Standard error 4.296# of samples 23




Zinc was much lower in the Black Creek samples than the Horsefly River in additionto being lower than the background, shown in Figure 3.17. The amount of Zn inthe Horsefly River decreased in the downstream direction, suggesting that thesource was further upstream of the sample sites with little to no Zn contributionafterwards. Since the Black Creek had a low amount of Zn in comparison, therewere reasonably no observed effects on the Horsefly River.

Figure 3.18 shows that Zn from the mine sediments had the highest proportionin the Fe/Mn oxide component, whereas other samples from the Black Creek andHorsefly River had Zn in all three components measured.

This is similar to the results found of the speciation of Cu (Figure 3.13), verifyingthat there were possibly greater amounts of sulphides and carbonates available inthe Horsefly River as Cu and Zn are commonly associated with each other.

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Figure 3.16: Zn concentrations [mg/kg] plotted against Al concentrations [%] forall sites.

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Figure 3.17: Zn concentrations [mg/kg] normalised against Al concentrations [%]from aqua regia digestion and sequential extracture procedure. Background con-centrations from sediment core plotted as a reference value.

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Figure 3.18: Percentage of Zn measured in the first three steps (exchange-able/carbonate, Fe/Mn oxides, sulphide/organic) of the sequential extraction pro-cedure.

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Chapter 4

Conclusions

The aim of this thesis was to investigate the spatial effects of the abandoned BlackCreek gold mine on the Horsefly catchment of British Columbia. Resuspendedsediment from the Horsefly River, channel bed sediment from the Black Creek andsource material from the mine were collected to prepare for geochemical analysis,particle size analysis and measurement of organic matter content. Total metal con-centrations and speciations of aluminum, arsenic, cadmium, copper, selenium andzinc from aqua regia digestion and sequential extraction was measured by ICP-OES. Background concentrations of the region were taken from the joint studyconducted by Vogels (2013), who explored temporal variations in the floodplainsoils of the Horsefly catchment. Linear regression analysis verified the direct rela-tionship between aluminum concentrations and percentage of clay (<2 µm) in thesamples. The relationships between aluminum and the other metals were also ex-amined by linear regression. Aluminum was then used as a normalising constituentto remove the effect of particle size on the heavy metal concentrations.

Resuspended sediment was collected either by a bucket or continuous centrifuge;the former is more convenient and supplies a larger, more representative sample.The two geochemical methods, aqua regia digestion and sequential extraction,yields similar results for total metal concentrations. However, concentrations fromaqua regia digestion are overall slightly higher than from sequential extraction. Themajority of metal concentrations is actually measured in the residual step after thesequential extraction procedure, but insights to the tendencies for metal speciationare still examined. While the direct relationship of aluminum and clay size is easilyconfirmed, no relationships between aluminum and the metals, excluding zinc, isfound in the sediments collected from the Black Creek. In these cases, the observedconcentrations of the metals are also taken into consideration.

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Sediment from the inactive mine is a clear source for metal input into the BlackCreek. This sediment contains elevated levels of arsenic in comparison to back-ground levels and upstream values. The creek is in turn a small source of sedimentinput for the Horsefly River, although there are signs of other larger metal inputsfurther downriver.

The acid-solube, exchangeable and carbonate-bound phase is the most susceptibleto environmental changes, whereas the other two phases, the reducible, Fe/Mnoxide phase and the oxidisable, organic/sulphide phase, are increasingly less so.The heavy metals in the Black Creek and Horsefly River are measured in higherconcentrations of the two less mobile phases whereas a study on an abandoned leadand zinc mine in central Wales had observed metals in the most mobile geochemicalphase (Byrne et al. , 2010). It is possible that historically there were higherconcentrations of metals in this exchangeable, carbonate-bound phase, but overtime had been transported and dispersed downriver towards Quesnel Lake.

As the majority of metal concentrations are essentially in the residual step of se-quential extraction, it implies that these metals are currently not mobile. Thiscould potentially lead to secondary diffusion, but only when environmental condi-tions drastically change.

The Black Creek mine is not presently influencing the Horsefly River despite someobserved local effects. In the past, arsenic levels attributed to the mine did affectdownstream Horsefly River, but decreased significantly as the mine scaled back itshydraulic operations (Vogels, 2013). This suggests that remote, small-scale mininghas the most minimal large impact on a watershed, but influences the immediatearea during active mining and a period of time after its closure. The abandonmentof the open pit did increase erosion and weathering rates and is a probable reasonfor the continual local influence of arsenic even after the closure of the mine.

There are two other abandoned mines upriver from Black Creek with possibleinfluence on the Horsefly catchment, but cannot be quantified without furtherresearch. There are many other mines depicted in Figure 1.3 that could alsoinfluence the watershed downriver of Black Creek closer to the town of Horseflyand delta at Quesnel Lake. These are only the documented locations of mines, asthere is a high likelihood of other numerous undisclosed mining locations. Suchincomplete records unfortunately do increase the difficulty with which to quantifythe local and regional influence of mining activities.

Salmon constitute a large interest for British Columbia, especially the fishing in-dustry and convservation groups, e.g. The Land Conversancy. Horsefly River isone of the major spawning sites, however metal concentrations measured are notsignificant enough to have affected the current populations of wild salmon. This

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also applies to other biota inhabiting the Horsefly catchment.

As this research’s results apply to low flow areas in August and September, itwould be of interest to study the seasonal variation of sediment geochemistry.Concentrations measured from sediment sampled over the course of one to twomonths could also be observed.

Although the closed gold mine at Black Creek has only minimal local arsenic inputsand no observed long-term effects on the Horsefly River, it is worth to considerthe combined effects of all the small-scale mines in the Horsefly catchment. Hencefor future research projects, it is suggested that the Horsefly River downstreamof Black Creek as well as the mines past the village of Horsefly towards QuesnelLake should be of particular focus. In addition, the overall influence of mining onQuesnel Lake from the Horsefly watershed should be quantified. The differencein sediment geochemistry of the abandoned copper and copper/gold mines mightalso be investigated in order to better understand the sources of metal inputs frommining activities in the Horsefly watershed.

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Appendix A

Detection limits of ICP-OES andICP-MS

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Element ICP-OES ICP-OES Watertaak Method ICP-MS UnitsAl 9.18 * 10-7 9.63 * 10-5 0.01 %As 0.0819 0.1953 0.1 ppmCd 0.00633 0.002688 0.01 ppmCu 0.0183 0.002493 0.01 ppmFe 1.281 * 10-6 1.632 * 10-5 0.01 %Mn 0.002106 0.01545 1 ppmSe 0.0873 0.0939 0.1 ppmZn 0.00384 0.00363 0.1 ppm

The ICP-OES Watertaak Method is used to analyse the residual fraction left overfrom the sequential extraction procedure.

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Appendix B

100% Stacked Columns of SequentialExtraction Procedure

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Appendix C

Observed Concentrations from Aqua RegiaDigestion and Sequential Extraction

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Appendix D

Observed Concentrations fromGeochemical Phases of SequentialExtraction

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