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(P886) The Effect of Kaolinite and Soil Organic Matter on the Hydrolysis of -Endosulfan.
Hengpraprom, Sarunya*,1, Lee, Cindy1, Coates, John1, Elzerman, Alan1, Klaine, Steve1, 1 Clemson University, Anderson, SC, USA
ABSTRACT- Endosulfan is an organochlorine insecticide that is still used throughout the world. Concerns about the use of this insecticide include its persistence, ability to accumulate in the food chain, and toxicity significance. Research efforts dealing with the processes affecting the transport of - endosulfan in soils are required to prevent further damage to surface water and aquatic organisms. Organic matter contributes significantly to the adsorption of pesticides in soil; however, in some cases mineral surfaces may also play an important role in the retention of these compounds in soil. Numerous studies have also reported the ability of mineral surfaces to catalyze the hydrolytic reaction of pesticides. This investigation was performed in order to determine the effects of organic matter and mineral surfaces on the hydrolysis of -endosulfan. In the first phase of this study, experiments were conducted using kaolinite suspensions and kaolinite plus soil humic acid (20 mgC/L) suspensions spiked with 0.333 ug/mL of -endosulfan. All suspensions were prepared at pH 8 and 25oC. During the experiment, suspensions were continuously mixed (end over end) in a dark room up to 45 hours (0, 2, 4, 6, 12, 21.5, and 45 hours). At the end of each sampling period, suspensions were centrifuged and the supernatant and solid pellet were extracted separately to determine the concentration of -endosulfan and its hydrolysis by-product, -endosulfan diol, in both fractions. Preliminary results indicate that adsorption to kaolinite is the dominant removal mechanism of -endosulfan during the first 6 hours of equilibration. In addition, -endosulfan diol was not detected at any time during the experiment indicating that both kaolinite and soil humic acid may delay the overall rate of hydrolysis of -endosulfan. Consequences of these results to the behavior of endosulfan in aquatic environments will be discussed.
Key words: α-endosulfan, adsorption, kaolinite, hydrolysis
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