Current‐ and past‐use pesticide prevalence in drainage ditches in the Lower Mississippi Alluvial Valley

Abstract

Pesticide application is common in agriculture and often results in applied pesticides entering adjacent aquatic systems. This study seasonally analyzed a suite of 17 current- and past-use pesticides in both drainage waters and sediments to evaluate the prevalence of pesticides in drainage ditches across the Lower Mississippi Alluvial Valley (LMAV). There were significantly higher concentrations (P<0.05) of current-use than past-use pesticides; however, there were consistently high numbers of detections of past-use pesticides in sediments. Sediment pesticide concentrations were an order of magnitude higher (150-1035 µg kg(-1)) than water samples (6-20.9 µg L(-1)). Overall, 87% of all samples analyzed for current- and past-use pesticides were non-detects. p,p'-DDT was detected in 47.5% of all drainage waters and sediments sampled. There were significant correlations (0.372≥r2≤0.935) between detected current-use water and sediment concentrations, but no significant correlations between past-use water and sediment concentrations. Overall, there was a high percentage (87%) of sediment and water samples that did not contain detectable concentrations above the lower limit of analytical detection for each respective pesticide. This lack of pesticide prevalence highlights the improved conditions in aquatic systems adjacent to agriculture and a potential decrease in toxicity associated with pesticides in agricultural landscapes in the LMAV.