METAL CONTAMINATION OF SEDIMENTS Cd, Pb AND Zn IN AURORA, MISSOURI Amanda Bybee; Advisor: Dr. Melida Gutiérrez Geology, Missouri State University, Springfield MO

ABSTRACT Aurora is a historic mining town in the Tri-state Mining District. Mining in the Tri-state district began in 1885 and ended by 1930. Mining waste (chat) was disposed in-piles for the most part. Remediation started in the area early in 2001, which continued through 2006. Metals (lead, zinc, cadmium) present in those piles might have reached sediments, posing a risk to water quality. This study will use fluvial surface sediment samples to plot current conditions of metal contaminants in the area and their distribution using ArcMap, followed by comparing them with the location where chat piles used to be. The sediment samples were allowed to air dry, disaggregated then sieved with 2 mm and 1 mm sieves. The samples were then analyzed for metals in a commercial lab. There are seventy-nine sediment samples with the following metal concentrations: cadmium with concentrations from 1.20 to 281.0 ppm with a median of 32.8 ppm, lead with concentrations from 42.0 to 8200 ppm with a median of 196.0 ppm, zinc with concentrations from 120.0 to 20400 ppm with a median of 3040 ppm. We compared sediment metal concentration data with stream sediment quality guidelines, to assess the possible threat to the health of the aquatic systems. The sediment quality guidelines for cadmium is values less than 4.98 have no effect, less than 10.0 have some effect and more than 10.0 found to be toxic. The sediment quality guidelines for lead is values less than 128 have no effect, less than 250 have some effect and more than 250 found to be toxic. The sediment quality guidelines for zinc is values less than 458 have no effect, less than 821 have some effect and more than 821 found to be toxic. Our maps show the locations where the metal content exceeded these guidelines.

Table 1 Cadmium, Lead and Zinc are still present in a wide range of values with a median of 32.8, 196 and 3040 respectively. The median for Cadmium and Zinc far exceed probable effect concentrations with severe effects set by MacDonald. (MacDonald, 2009)

MINERALIZATION

SEDIMENTS QUALITY GUIDELINESSediment guidelines are necessary because of the impact on organisms directly and indirectly through the food chain. Sediments hold a memory of current and historic toxicity of the water. The toxic metal levels can affect the health of organisms in many ways including survival, growth, and reproduction. Sediment quality guidelines have been established for the Tri-State Mining district (MacDonald, 2009). There is a range of toxicity levels with each contaminant. MacDonald reported guidelines for the Tri-State Mining district for this range for several species. These metals include cadmium, copper, lead, nickel and zinc. The criteria for each level of toxicity is “<20% incidence of toxicity below the toxicity threshold, >50% incidence of toxicity above the toxicity threshold, and >80% of the samples correctly classified as toxic and not toxic” (MacDonald, 2009). Cadmium values less than 4.98 have no effect, less than 10.0 have some effect and more than 10.0 found to be toxic. Lead values less than 128 have no effect, less than 250 have some effect and more than 250 found to be toxic. Zinc values less than 458 have no effect, less than 821 have some effect and more than 821 found to be toxic.

RESULTS

3

CONCLUSIONSMining in the area ended by 1930 and remediation ended in 2006. Even though more than 8 years have passed since remediation finished metal levels in area stream sediments continue to affect the stream quality and are potentially toxic to aquatic life and the food chain.

WATERSHEDS

R E F E R E N C E S

GeoSTRAT – Geosciences Technical Resource Assessment Tool. Retrieved February 15, 2015, from http://dnr.mo.gov/geology/geostrat.htmGutierrez, M, Wu S, Peebles J. Geochemical mapping of Pb- and Zn-contaminated streambed sediments in southwest Missouri, USA, In review.MacDonald, 2009, Development and Evaluation of Sediment and Pore-Water Toxicity Thresholds to Support Sediment Quality Assessments in the Tri-State

Mining District (TSMD), Missouri, Oklahoma, and Kansas. Trimble JC, 2001, Spatial patterns and floodplain contributions of mining-related contaminants in Chat Creek watershed, southwest Missouri, M.S. Thesis,

Missouri State University, Springfield, MO

PICHER, OK

AURORA AREA MINING SITES

AURORA AREA AFTER REMEDIATION

Effects on Organisms (in ppm)

No effect

Some effect

# of Samples above some effect/

# of Samples tested

Severe effect

Cd <4.98 >4.98 35/44 >10.0

Pb <128 >128 59/79 >250

Zn <458 >458 77/79 >821

MethodsThe sediments were collected from the surface down 3 inches below the surface. The samples were collected with a spade and contained within plastic bags approximately 4 hours, until we were able to get them back to the lab. Samples were immediately put on wax paper to air dry. Rocks and organic material like leaves were removed. Dried samples were then disaggregated with a mortar & pestle then sifted with a 2mm sieve then 1mm sieve. Samples were then sent to ALS USA where they were analyzed using standard procedure of acid digestion (aqua regia) and ICP-MS. I then plotted the concentrations for Cadmium, Lead, and Zinc using ArcGIS.

SAMPLING IN CHAT CREEK

Cd Pb Zn 10

100

1000

10000

ZINC

CADMIUM

LEAD

N=79

N=44

N=79

Gutierrez, Wu, Peebles

No effectSome effectSevere effect

No effectSome effectSevere effect

No effectSome effectSevere effect