GEOCHEMICAL ASSESSMENT OF THE IMPACT OF POULTRY LITTER APPLICATION ON TRACE ELEMENT DISTRIBUTION IN BROADKILL RIVER SEDIMENTS, DELAWARE, USA

This project examined the impact of long-term litter application on the chemical signatures of As, Cu, Zn, P and S in river sediments of Broadkill River watershed within the Delmarva Peninsula, a region of intense poultry production. Twenty-seven (27) sediment samples were collected from Broadkill River drainage systems and analyzed for trace elements, plant-extractable elements, and basic soil parameters such as particle size, organic matter and soluble salts. Results showed that concentrations of the trace elements in stream sediments are approximately log-normally distributed. Spatial variability in concentrations of trace elements was evident, with most elements increasing in concentration from upstream headwaters to downstream reaches draining predominantly agricultural areas. Using GIS maps with overlays of hydrology and land use activity, statistical correlations between the concentrations of As, Cu, Zn and P and agricultural activities within the watershed were examined. Results indicated positive correlation between the trace elements, but there was no significant correlation of elements to a specific land use (forest, agriculture, residential). Trace elements were also positively correlated with percent of clay and silt particles, indicating that these elements partition to finer grain sizes. Calculations of element enrichment factors and the geoaccumulation index revealed that most of our sediment samples were not enriched with respect to trace elements in comparison with our reference samples. Several samples showed trace element enrichment, which may be related to anthropogenic activities, but the enrichment is not correlated with a specific land use. Overall, our results do not show a clear connection between historic poultry litter application and trace element concentrations in stream sediments of the Broadkill River watershed.