Surface water, ground water and sediment quality in three oxbow Lake watersheds in the Mississippi Delta Agricultural Region: pesticides
2003
Cooper, Charles | Smith, Sammie Jr | Moore, Matthew
We measured residual and current use pesticides in shallow groundwater, surface water, and lake sediment in three oxbow lakes and their watersheds in the intensively cultivated alluvial plain of the Mississippi River, USA. The three year study focused on providing knowledge of pesticide movement and concentrations from intensive agricultural production and evaluating the degree of contaminant deposition and persistence in oxbow sediments. Penetration of insecticides into shallow groundwater did not represent a hazard. Herbicides and insecticides were found in surface water as a result of rainfall related runoff. Atrazine had the largest number of detections (28% of lake water samples). Sediment cores taken for pesticide analysis were also viewed by age each in each lake. Residual organochlorines dominated the pesticide sediment profile. DDT and its metabolites were the only compounds which permeated sediments at all sites. Sediments deposited in the 1960s and 1970s which contained higher concentrations of DDT have been effectively sealed by more recent material so that the sink of contaminant is unavailable to the water column. Controlled release of pyrethroid insecticides in a forested wetland showed that the wetland was totally effective in neutralizing the pyrethroids before they reached lake surface water. Pesticides seldom exceeded drinking water standards. Acute toxicity concerns lessen as more conservation measures are installed on and off fields. Additionally, DDT metabolites continue to slowly degrade.
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