Dissolution of Trace Elements From Coal Fly Ash As Affected by Citrate.

In December 2008, 1.1 billion gallons of coal fly ash slurry were released following a dredge cell failure at the TVA coal-fired power plant in Kingston, TN.  Although most of the ash that had inundated the Emory and Clinch Rivers has been removed, the long-term environmental impacts of any residual ash is unknown. Our goal is to determine the mobility and trophic transfer of potentially toxic trace elements from coal fly ash in relation to chemical speciation and biogeochemical conditions in sediments.  The specific objective of this research was to determine how complexing organic acids solubilize potentially toxic trace elements and matrix elements from coal fly ash. Citrate at concentrations between 0 to 30 mmol/kg ash was reacted with fresh fly ash at pH 10 for 72 hours in aqueous solutions of 0.01 M KCl. Aqueous filtrates were analyzed for dissolved trace elements (Zn, Cu, Cr, As, Se, U, Pb, Sr, and Mn) and matrix elements (Si, Al, Fe, Mg, Ca, and K). Dissolved concentrations of most elements increased with increasing citrate concentration, indicating that complexing organic acids produced in sediments can mobilize trace elements.