Arsenic Distribution In Soil Profiles Amended With Coal Combustion By-Products

Abstract

Combustion of coal in the generation of electric power produces large quantities of waste ash that is typically landfilled or stockpiled on site. This material may be applied to agricultural land, thereby avoiding disposal costs, if no adverse environmental consequences result. Several trace elements such as arsenic, boron, and selenium have been found in high concentrations in some fly ashes. In this study, fly ash and a desulfurization gypsum byproduct produced by power plants were applied to two soils in the field at rates of 20 int/ ha, both singly and in mixture. Soybean followed by corn was grown on the plots, and soils sampled with depth at the end of the second season and analyzed for extractable arsenic (As). Arsenic was found to be quite immobile in both soils studied as assayed by acid extraction, although more mobile in the sandier Lakeland than in the Cecil soil. Extractable As in Cecil soil was not different on amended plots vs. controls due to the high pesticide-derived As levels. In sandier Tifton soils, fly ash tended to increase extractable As in topsoils above control levels, but low levels (< 100 ppb) were found below 50 cm depth. Desulfurization gypsum added much less As to soils than did fly ash. We conclude that on very sandy soils, some increase in As availability and leaching potential may occur with high loadings of fly ash materials; plant uptake studies are underway to assess the magnitude of this effect.