Sally Maharaj¹, Christopher Barton^1*, Bon-Jun Koo¹, and Lee Newman²

¹University of Kentucky, Department of Forestry, Thomas Poe Cooper Bldg., Lexington, KY 40546-0073, USA
²University of South Carolina, Arnold School of Public Health, 800 Sumter St, Columbia, SC 29208, USA

Abstract
The 488-D Ash Basin (488-DAB) is an unlined, earthen landfill on the U.S. Department of Energy’s Savannah River Site, SC that contains approximately one million tons of coal combustion wastes (CCWs). Pyrite that is co-mingled with the CCWs has undergone oxidation and formed sulfuric acid, which has dissolved metals and trace elements in the CCWs and facilitated their mobility. The acid leachate contributes to groundwater deterioration in the area and threatens biota on, and adjacent to, the landfill. A study was undertaken to examine CCWs and vegetation on the 488-DAB to assess the potential for phytoavailability of these elements and to determine if a secondary contamination source exist. Results indicated that trace element concentrations of the CCWs were higher than those of native soils in the area. Mean pH (1.79 + 0.75) and As concentrations (64.7 + 43.0 mg kg^-1) for the CCWs were in the range of critical plant toxicity. Sequential extractions of the CCWs indicated that Mn, Zn, Ni, and Cr were organically bound and in exchangeable fractions in the material and likely phytoavailable, while Pb and Se were tightly bound in the crystalline and acid extractable (residual) fractions. The fractionation patterns for Al, As, Cd and Fe were very similar with most bound to the poorly crystalline fraction, which suggest that their solubilities are likely controlled by a common precipitate or mineral in the CCWs. Tissue analysis indicated that Mn and Zn were accumulated by species growing on the 488-DAB, as predicted. However, Ni and Cr were not accumulated at levels above that of the CCWs. Uptake of Se and Cd in tissue was observed at levels over that of the CCWs in several species, but not all. Given these conditions, results suggest that periodic monitoring of plant species growing on the 488-DAB should continue to ensure that toxicity and secondary contaminant problems do not arise.