THE RELEASE AND TRANSPORT OF ARSENIC AND OTHER TRACE ELEMENTS FROM A POULTRY LITTER APPLICATION IN AN AGRICULTURAL WATERSHED

Trace element contamination of water in agricultural watersheds is a recent concern, as poultry litter applied to croplands can release organoarsenic, as well as other poultry feed additives (i.e. copper) to the environment. Arsenic and copper released from natural and anthropogenic sources are often assumed to adsorb to mineral surfaces and consequently remain immobile in soils. While some studies have shown that this does occur, recent data suggest that arsenic and copper associated with particles and colloids can be transported from litter-applied croplands to soil water, groundwater and stream water. A small-scale field application of poultry litter was conducted at our research site in Rockingham Co. Virginia in early August 2006. Soilwater samples were collected from lysimeters before application to characterize background hydrogeochemistry, and successive water samples were collected monthly for a total of four sampling periods. The water samples were then field filtered, with subsets of the filtered water retained for subsequent laboratory analysis. Ultrafiltration was also conducted to aid in the determination of the degree of association of the arsenic and copper with colloidal, macromolecular, or particle phases within the soil. Our litter application was successful, as many ions were released into the soil water directly after our litter application. Species such as organic carbon, sulfate, nitrate, and chloride moved quickly through the subsurface, while species such as arsenic, copper, and zinc were transported more slowly. Our data also suggest that the arsenic and copper released from the application were not only dissolved, but are also associated with particles, colloids, and macromolecules.