Submitted to: Journal International Environmental Application and Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2007
Publication Date: 7/1/2007
Citation: Knight, S.S., Lizotte Jr, R.E., Smith Jr, S., Bryant, C.T. 2007. Distribution and spatial variation in surface sediment pesticides of Mississippi alluvial plain. Journal International Environmental Application and Science. 2(3&4):40-50. Interpretive Summary: Insecticides are vital in maintaining agricultural production in the Mississippi Delta. Extent and concentration of contamination by pesticide depends on several factors such as distance from the source of contamination and decomposition rates. Seventeen current and historic-use pesticides were measured in lake sediments from nine oxbow watersheds from June-July, 2004. Comparisons of sediment pesticide concentrations among watersheds showed two patterns. The first was controlled by agricultural land-use practices in and around these watersheds that received runoff during storms. The second pattern was determined by the degree of flow-through that occurred with in the lakes. Results also show that despite the fact that some watersheds had extensive riparian areas available to process contaminants, these watersheds still receive significant amounts of current-use pesticides and that application of best management practices surrounding the watersheds lessens the degree of contamination. These results show the importance of conservation practices in reducing pesticide contamination.
Technical Abstract: Insecticides play a vital role in maintaining agricultural production especially in the Mississippi Delta. Extent and concentration of contamination by pesticides depend on several factors such as flow path length from source to receiving water as well as residence time and decomposition rates. Nine oxbow lakes were categorized according to land use and implementation of agricultural best management practices (BMPs). Three sites located in a National Wildlife Refuge (NWR) were selected as reference sites. Seventeen current and historic-use pesticides were measured in surface sediments (5 cm depth) from theses nine watersheds from June-July, 2004. Comparisons of sediment pesticide concentrations among watersheds revealed spatial patterns. Statistically significant (P </= 0.05) variation occurred in 10 of 17 pesticides measured. Patterns of pesticide contamination were indicative of agricultural land-use practices in and around these watersheds with influxes of materials occurring during storm events. Additionally, the degree of static or flow-through conditions within each watershed was found to be important, with some watersheds (BMP) receiving little or no additional flow from neighboring riverine systems compared with other more open watersheds (NWR) with extensive flood plains allowing greater transport of contaminants. Results show that despite reference (NWR) watersheds having extensive riparian areas available to process contaminants, these watersheds still receive a significant influx of current-use pesticides and that application of BMPs surrounding similar watersheds can lessen the degree of contamination.