IMPACT OF DISSOLVED ORGANIC CARBON (DOC) ON THE MOBILITY OF POULTRY LITTER DERIVED SOLUTES (AS, CU, P, AND ZN) WITHIN AGRICULTURAL WATERSHEDS

Column experiments were used to examine the interaction between poultry leachate and soil from Delmarva Peninsula, a region of intense poultry production. The main objective of the experiments was to determine the extent to which dissolved organic carbon (DOC) in poultry litter enhances mobility of litter derived-elements (As, Cu, P and Zn) from litter into solution. Soils were collected from a field site near Milton, DE. After initial pretreatment, soil was packed into PVC columns. The soil columns were subjected to two solution treatments: poultry litter leachate and simulated solution of similar element concentrations, pH, and ionic strength but without DOC. Results of the experiments showed that DOC enhanced the mobility of all of the elements of interest. Cu was fully mobilized into solution and was not retained in the soil. However, even in the presence of DOC, 60-70% of As, P, and Zn was retained within the soil. Patterns of breakthrough curves (BTCs) and mass calculations suggest that the behavior of these elements is controlled by both adsorption (including competitive) to soil and complexation with DOC. Although DOC mobilized 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, suggesting that complexation to solid organic matter likely aids 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 elements derived from litter.