ASSESSMENT OF ARSENIC AND TRACE METAL CONTAMINATIONS IN RIVERINE WATER AND SEDIMENTS RESULTED FROM THE COAL ASH SPILL IN KINGSTON, TENNESSEE

In 2008, the north dam of the Kingston Fossil plant waste pond ruptured allowing 4.1M m³ of coal ash to flood into the Emory River, Clinch River, and Watts Bar Reservoir in Eastern Tennessee. This ash contained high concentrations of arsenic and other trace metals, which are toxic to the environment. Most of the 2-year remediation efforts by the Tennessee Valley Authority (TVA) and the Environmental Protection Agency (EPA) included the physical removal of coal ash via hydraulic dredges. The goals of this study are to determine current contamination levels of arsenic and trace metals and evaluate the effectiveness of clean-up efforts 8 years after the spill. In spring 2016, water samples were collected from 7 contaminated and 3 uncontaminated portions of the river systems for chemical analysis. Additionally, 6 sediment cores (~30 cm long) were collected and analyzed for water-soluble and acid-leachable metals. Results have been compared to the maximum contamination level (MCL) guidelines established by the EPA for human health and aquatic life. We have found that the water column in the studied rivers is largely free of arsenic and trace metals. The analyzed river sediment samples, however, show high concentrations of arsenic and trace metals. Arsenic exceeded the human health MCL in water leaching experiment by 3-200x (where x means times) and acid leaching by >3,000x. Other water-soluble metals that exceeded the aquatic life MCLs were: Al (6-1,840x), Cr (10x), Fe (0-7x), and Zn (33x), while Se (0-5x) exceeded the MCL for human health. The acid-leachable metals in 2% HCl that exceeded the aquatic life MCL were: Cd (79-346x), Cr (4-146x), and Pb (12-310x) and Se (1-16x), while Ba (4-181x), Cu (0-18x), Mn (104-1,150x), Ni (0-26x), Se (0-2x), and Tl (58-1,720x) exceeded the MCLs for human health. Our results indicate that aquatic organisms and people using the water are in no immediate danger from remaining contamination by arsenic and trace metals. While the arsenic and trace metal concentrations appear to be smaller (≥60x) in the top river sediments compared to similar analysis done within 1 year of the ash spill, the trace metals remain elevated and raise concern. They pose a great threat to benthic organisms and could potentially affect the water quality, if the conditions become acidic in the future.