Transport and fate of atrazine and lambda-cyhalothrin in an agricultural drainage ditch in the Mississippi Delta, USA

Drainage ditches are integral components of agricultural production landsca pe, yet their contaminant mitigation capacity has been scarcely examined. I f ditches are indeed capable of contaminant mitigation, then their use may serve as an alternative agricultural best management practice (BMP). A 50 r a portion of an agricultural drainage ditch, located in the Mississippi Del ta Management Systems Evaluation Area (MDMSEA), USA, was amended with a mix ture of water, atrazine , (2-chloro-4-ethylamino-6-isopropylamino-s-triazin e) (herbicide) and lambda-cyhalothrin (lambda -cyano-3-phenoxybenzyl-3-(2-c hloro-3,3,3-trifluoroprop-1-enyl)-2,2-dimethyl cyclopropanecarboxylate) (in secticide), simulating a storm runoff event. Pesticide amendment was achiev ed using a diffuser to disperse the mixture at an inflow point along the di tch (designated as "0 m"). Pesticide concentrations in water, sediment, and plants were monitored for 28 days. One hour following initiation of simula ted runoff, mean percentages of atrazine concentrations measured in water a nd sediment were 37 and 2%, respectively, while mean percentages of lambda- cyhalothrin concentrations in water and sediment were 12 and 1%, respective ly. Atrazine and lambda-cyhalothrin mean percentage concentrations in plant s (Polygonum (water smartweed),Leersia (cutgrass), and Sporobolus (smutgras s)) were 61 and 87%, respectively. Therefore, plants serve as an important site for pesticide sorption during runoff events. Aqueous concentrations of both pesticides decreased to levels which would not elicit non-target toxi cological effects by the end of the 50 m portion of the drainage ditch. Thi s research provides fundamental answers concerning the capability of vegeta ted agricultural drainage ditches to mitigate pesticide-associated storm wa ter runoff. Published by Elsevier Science B.V.