Master of Science (MS)
Pesticides are used globally and are often found within bodies of water. The EPA investigates the potential environmental impact through computer modeling in order to help mitigate some of the regulatory burden of pesticide fate investigation. Currently when pesticides enter a water body, the Exposure Analysis Modeling System (EXAMS) estimates partitioning depth as 5 cm and assumes equal distribution. This assumption was tested with a wide variety of pesticides with varying Koc ranges and water solubilities. Savillex 150 ml Teflon tubes were filled with wetland and ricefield sediments with fresh and seawater as the aqueous phase. The seven pesticides tested included, quinclorac, bentazon, 2,4-D, atrazine, dicloran, flutolanil, and trifluralin had reported Koc ranges as low as 20 and as high as 15800. Pesticides were sprayed onto the top layer of water and allowed to partition over 24 hours. Once suspended, 0.5 cm segments were sonicated and analyzed by Agilent 1260 Infinity High Performance Liquid Chromatography. Normalized applied mass percentages were calculated by comparison to pesticide standards that ran simultaneously with all samples. The majority of pesticides were found in the overlying water layer and within the first 0.5 cm of sediment. Salinity of the aqueous phase was shown to increase pesticide sediment concentration, but did not increase partitioning depth.
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Marsh, Brendan Michael, "Pesticide Partitioning In Louisiana Wetland Aand Ricefield Sediment" (2016). LSU Master's Theses. 4478.
Available for download on Saturday, February 23, 2019