|Smith, Jr, Sammie|
|Shields Jr, Fletcher|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 6/1/2009
Publication Date: 1/1/2010
Citation: Farris, J.L., Milam, C.D., Moore, M.T., Bennett, E.R., Cooper, C.M., Smith, Jr, S., Shields Jr, F.D. 2010. Evaluating toxicity of atrazine and lambda-cyhalothrin amendments in agricultural ditch mesocosms. In: Moore, M. T. and Kroger, R. (Eds.), Agricultural Drainage Ditches: Mitigation Wetlands for the 21st Century. Research Signport. Kerala, India. pp. 223-228.
Interpretive Summary: Drainage ditches are important agricultural landscape features that transport excess water from crops into receiving aquatic systems. Because they have characteristics of wetlands, these ditches are able to reduce the amount of contaminants associated with runoff water before they enter rivers, lakes, or streams. Bioassays were conducted on water and sediment collected from an agricultural drainage ditch in the Beasley Lake watershed. While initial samples of water were harmful to the survival of aquatic invertebrates and fish, after 48 h, these same organisms were able to survive in collected ditch water. Bioassays conducted with ditch sediment (soil) showed they were initially harmful to exposed invertebrates, and they continued to be harmful even 28 days after initial sample collections. This demonstrates how ditches are able to clean up water before it enters lakes, rivers, and streams. It also shows how chemicals are transferred and persist in other compartments (like sediment / soil).
Technical Abstract: Ditches running throughout and adjacent to agricultural lands serve primarily to remove and store excess water associated with storm events. More recently, these edge of field delivery systems have been investigated for their ability to mitigate potential contaminants. Six sites along a 50-m segment of agricultural ditch located in the Mississippi Delta Management Systems Evaluation Area (MDMSEA) were used to measure fate and effects of an atrazine (triazine herbicide) and lambda-cyhalothrin (pyrethroid insecticide) mixture. These measurements were then utilized to evaluate the use of these systems in potentially decreasing effects to downstream receiving systems. Following a simulated runoff event, aqueous and sediment samples were collected and analyzed spatially (6 sites) and temporally (0.5h – 28d). Water sampled from specific sites illustrated that toxicity progressed downstream throughout sampling intervals. Ceriodaphnia dubia and Pimephales promelas did not survive 48-h exposure to water collected from downstream sites; however, survival did occur in succeeding collections by or before 28 days (>97% survival). Sediment tests (10-d) with Chironomus tentans indicated persistent toxicity at the point of application through 28 days, and significantly reduced midge growth at all collected sites. C. tentans continued to exhibit impairment (growth) for 28 days following application, with sediment concentrations of 92.5 ug/kg (atrazine) and 29.1 ug/kg (lambda-cyhalothrin). This study focused on validation of organism responses in dynamic agricultural systems that provide mitigation for contaminant transfer and transformation.