HAZARDOUS METALS IN TENNESSEE COPPER BASIN STREAM SEDIMENTS: SOURCES, CONCENTRATIONS AND DISTRIBUTIONS

The Tennessee Copper Basin, southeast Tennessee, is an area affected by over 100 years of mine-impact degradation to regional landscape, flora, and fauna. Early mining and ore processing techniques resulted in stripping of the landscape for wood fuel and the production of atmospheric sulfuric acid. The resulting acidic rains and oxidation of bedrock sulfide minerals sterilized the soil, resulting in long-term erosion of metallic elements into the local watershed. Although mining operations ceased in 1987, the Copper Basin still exhibits signs of environmental stress. Numerous past studies have investigated the toxic metal concentrations in the Copper Basin Watershed, but few recent studies have focused on the toxic metal load present in the stream bed sediments. The purpose of this study is to determine whether or not toxic elements are mobile within the stream sediments, and how quickly toxic metals concentrations attenuate or enrich with respect to distance from potential contaminant sources. The study focuses on five toxic metals: arsenic, cadmium, lead, thorium, and uranium. Approximately 60 samples were collected for analyses in streams and rivers in the Copper Basin watershed, as well as samples from outside the watershed as background concentration comparators. Samples also were collected from localities immediately downstream of tailing ponds, considered to be the metal sources. Samples were analyzed by both x-ray fluorescence and inductively coupled plasma mass spectrometry. Attenuation/enrichment rates for each metal were calculated by comparison of metal concentrations at the tailing pond source sample localities to concentrations at down stream sample sites. Results show the presence of As ≤ 44 ppm, Pb ≤ 244 ppm, and U ≤ 32 ppm. Calculated attenuation/enrichment rates are: As = -0.3 ppm/km, Cd = -0.9 ppm/km, Pb = + 1.6 ppm/km, Th = + 0.1 ppm/km, U = + 0.03 ppm/km. The research has direct implications to long-term environmental and health studies of the Copper Basin.