RAPID: Trace Element Cycling in Dan River Sediments following Coal Fly Ash Release

1439743

Heyes

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. This study will provide information to policy makers on the extent to which coal fly ash releases present a hazard to humans and wildlife. Specifically it will address the extent to which trace elements continue to be released from ash enriched sediments and if the depositional environment influences such release. This research will help determine if sediment removal is warranted and to prioritize any removal efforts based on the environment of deposition and proximity to targets of concern such as drinking water intakes and sensitive areas for the rivers fishery and recreational use.

This proposed research seeks to assess the impact of ash on sediment biogeochemistry as it pertains to the bioavailability and toxicity of ash born trace elements. Particular emphasis is placed on the sediment redox condition as this impacts metal speciation and mobility in sediments. It is understood that development of anoxic conditions in sediments promotes the release of trace elements through changes in speciation. It is hypothesized this will occur in the case of coal fly ash. The research will focus on the release of trace elements As, Se, Hg and MeHg to porewater as indicators of trace element mobility, transformation and bioavailability. It has also been proposed that trace element mobility is enhanced through a direct interaction with sulfur or indirectly through sulfurized organic matter. The research will investigate the degree of sulfurization of DOM in sediment porewater to assess if this is a potential mechanism for trace element mobilization and transport.