|Smith Jr, Sammie|
|Shields Jr, Fletcher|
Submitted to: Society of Environmental Toxicology and Chemistry (SETAC)
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/1999
Publication Date: N/A
Technical Abstract: Agricultural ditches remove and store excess water associated with storm events. Little is known of their ability to mitigate potential contaminants. Samples along a 50 m agricultural ditch in the Mississippi Delta Management Systems Evaluation Area (MDMSEA) were collected to evaluate fate and effects of atrazine and lambda-cyhalothrin. Following a simulated runoff event, aqueous and sediment samples were collected (and analyzed) spatially (6 sites) and temporally (0.5 h - 28 d). Aqueous experiments (48 h) with Ceriodaphnia dubia and Pimephales promelas measured toxicity (0% survival) in downstream sites until recovery occurred by or before 28 days (>97% survival). Sediment experiments (10 d) with Chironomus tentans indicated persistent toxicity at the application site through 28 days and significantly reduced midge growth at all collected sites. Aqueous and sediment pesticide concentrations and observed test organism responses suggest that atrazine movement drove aqueous toxicity 24 h following application. C. tentans continued to elicit impairment 28 d following application, with sediment concentrations of 92.5 ug/kg (atrazine) and 29.1 ug/kg (lambda-cyhalothrin). This research focuses on organism response - validation in dynamic agricultural systems that provide mitigation for contaminant transfer and transformation.