METALS AND HUMAN HEALTH: THE CHARACTERIZATION OF TOXIC METALS FROM MINE WASTE AT THE TAR CREEK SUPERFUND SITE AND ASSESSMENT OF EXPOSURE TO THE TAR CREEK COMMUNITY

The mine waste (chat) piles at the Tar Creek Superfund Site in Northeast Oklahoma contain high concentrations of lead, zinc, and cadmium. Wastes from the mines impact the surrounding ecosystems and continue to pose a potential risk to human health in the area. The objective of this research is to determine the concentration of toxic metals in the mine waste piles, characterize the mineralogy, determine the chemical inter-variation and intra-variation of the chat piles, and assess the risk of exposure of toxic metals to the surrounding community. To meet the objectives, samples of chat have been extracted from the site and analyzed using X-ray fluorescence (XRF), and X-ray diffraction (XRD) techniques. XRF is used to measure the total concentrations and XRD is used to characterize the mineralogical phase of lead, zinc, and cadmium in the chat pile samples. XRD will aid in the explanation of the bioavailability of these metals. Chat pile samples were taken from a 2-4 cm layer below the surface of each pile (in six piles located throughout the Tar Creek Site.) Two to four locations at each pile were sieved into eight different size fractions ranging from >4 mm to <0.037 mm. XRF results demonstrate that the intrapile range in concentration of zinc (approx. 4000-15000 ppm) varies less than the interpile range in concentrations (approx. 5000-25000 ppm.) The results demonstrate consistent increase in Zn, Pb, and Cd concentration with decreasing particle size. In many cases, the metal concentrations in the <0.037 mm fraction were at least an order of magnitude greater than those present in the >4 mm size fraction. The chat in the <0.037 mm size fraction is respirible and important for exposure assessment. Initial XRD results suggest that Galena, Sphalerite, Cerrusite, Hydrozincite and Hemimorphite are some of the mineralogical phases of the metals of interest present in the chat piles at the <0.037 mm size fraction. Further research will focus on determining if the variation in metal concentration is due to primary mineralogical differences or is the product of differential weathering and other environmental factors. The XRF and XRD data will inform the cooperative project testing soil, water, food, crops, and house dust for exposure assessment.