On February 2, 2014, the third-largest coal ash spill in the Nation occurred at Eden, North Carolina where a drainage pipe under a 27-acre Duke Energy Dan River Steam Plant waste pond collapsed, discharging coal ash and millions of gallons of contaminated water into the Dan River. The Dan River originates in Virginia and flows into North Carolina and then flows north back into Virginia crossing the state lines eight times. It eventually flows into the Roanoke River, and into Lake Kerr then Lake Gaston and eventually into the Albemarle Sound, NC. The waters serve as a highly used recreation system and as a source of drinking water for cities from Danville, VA to as far away as Virginia Beach. The toxic constituents of coal ash include various contaminants from metals such as arsenic (As), lead (Pb), mercury (Hg) to selenium (Se) along with a suite of organic compounds. While the element concentrations in impoundment water can exceed drinking water criteria and aquatic life water quality criteria, less is known about the fate of trace elements bound to ash in the new biogeochemical environment of the Dan River. Dissolution and changes in speciation can increase metal toxicity thus threaten wild life and water usability for years to come. To answer some of these questions a multidisciplinary approach is necessary. The proposed work should provide a clearer picture to environmental agencies and water managers of the extent, transport time scales, and removal processes of coal combustion residue-derived pollutants in this river system.
This project will provide unique insight into the evolution of coal combustion residue-derived contaminants in the basin over longer time and spatial scales, and at levels that may be considered below immediate remediation targets but are still important for the overall biogeochemical function and health of the aquatic ecosystem. The development and application of novel and independent geochemical tracers for coal combustion residue input will help remove some of the ambiguity associated with data on contaminant concentrations, and identify the extent of coal combustion residue inputs even in the absence of action levels of contaminants. While the initial focus by the state/federal agencies and other organizations has been on identifying the levels of contaminants in the coal combustion residue pond outflow and the river, there are several techniques which allow scientists to trace the response of the system in time and length scales consistent with the transport of coal combustion residue to the Kerr Reservoir. This proposed research will provide tools to track the concentrations of major, minor and trace elements as well as the stable isotope S-34 (sulfur-34) in water and sediments in the Dan River in the post-spill period. Because germanium (Ge) is enriched in coals and should act as a conservative tracer, we expect Ge to be anomalous and Ge/Si (silicon) ratios to be a unique fingerprint for coal combustion residue input. It is thought that the As/Ge; (chromium) Cr/Ge and other trace element/Ge ratios should be a powerful tools for identifying coal combustion residue-related anomalies in those elements. The stable isotopic analysis of S-34 in dissolved sulfate will act as a second constraint on the coal combustion residue input that can be compared to the Ge/Si and trace element/Ge ratios. This RAPID funding is to provide funds to continue a sampling and analysis program begun in the immediate aftermath of the spill. Both river hydrologic process and biogeochemical processes are expected to significantly modify and attenuate the immediate impacts of the contamination event. It is vital to establish and continue a regular sampling program in order to assess the impact of transport and biogeochemical removal on contaminants of concern.
