USING COLUMN EXPERIMENTS TO EXAMINE TRANSPORT OF ARSENIC AND OTHER ELEMENTS RELEASED FROM POULTRY LITTER: IMPLICATIONS FOR TRACE ELEMENT MOBILITY IN AGRICULTURAL WATERSHEDS

This study examined the effect of dissolved organic matter in poultry litter leachate on the fate and transport of litter-derived elements, As, Cu, P and Zn, using laboratory column experiments with soil collected from a field site on the Delmarva Peninsula, a region of intense poultry production. Treatments included leachate and simulated litter solution, which was prepared using similar concentrations of trace elements and major ions, as well as similar pH, ionic strength, but without DOC. Results of the experiments showed that DOC enhanced the mobility of all of the trace elements, but that even in presence of DOC, 60-70% of Zn, As and P were retained within the sediment. Cu was fully mobilized in solution and was not retained in the soil. Patterns of breakthrough curves (BTCs) and mass calculations suggest that the behavior of these trace elements in the column is controlled by both adsorption (including competitive) to soil and complexation with DOC. Although DOC mobilized trace elements in the column experiments, results from other field studies shows elevated Cu and Zn in topsoils to which litter has been applied over the long-term, indicating that complexation to solid organic matter will aid in retention of these elements at the surface. The implication of these findings is that the presence of DOC in poultry litter, in addition to the organic matter content and mineralogy of soils and underlying sediment, all strongly influence the mobility of trace elements derived from litter.