PESTICIDE STRATIFICATION IN AN ENGINEERED WETLAND DELTA

Recent studies analyze variations in pesticide retention and leaching through soils of different textures. Sample collection procedures are based on these results showing faster leaching and less retention in c oarser-grained, organic-poor soils, relative to fine-grained, organic- rich soils. However, these studies deal with soils formed over long pe riods of time, characterized by vertical transport of pesticides. Engi neered wetlands are a means of reducing surface water contamination fr om pesticides. To assess the effectiveness of this technology, input o f pesticide-laden sediment must be determined. Undisturbed cores withi n the prograding delta at Blue Creek wetland are correlated using visu al and physical descriptions and characterized using GC-ECD to determi ne influx of adsorbed pesticide during delta development. Because the delta forms much faster than soil horizonation, delta sediments allow data correlation with distinct periods of time and season. Data indica te a better correlation of pesticide content with season than with tex ture or organic matter content for these sediments. Analyses of only t he fine-grained or organic-rich sediments would have resulted in misle ading data on loading or degradation rates within the wetland. Through careful monitoring of the progression of the delta throughout the com ing years, a very accurate assessment of contaminant fate within the w etland will be documented.