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PT07 Contaminated Harbor and River Sediment
(PT126) Degradation kinetics of selected organophosphate and carbamate insecticides in urban creek sediments.
Bondarenko, Svetlana1, Gan, Jay1, 1 Department of Environmental Sciences, University of California, Riverside, Riverside, CA, USA
ABSTRACT- Organophosphate and carbamate insecticides have been frequently detected in urban streams. Due to their acute toxicity to many aquatic organisms, compounds such as chlorpyrifos and diazinon have become target toxics in the TMDL program. A number of OPs and carbamates have been detected in the San Diego Creek/Newport Bay watershed. However, there is very little site-specific information about their persistence in the urban creek sediments. We studied the degradation kinetics of chlorpyrifos, diazinon, malathion and carbaryl in San Diego Creek and Bonita Creek sediments under both aerobic and anaerobic conditions. Malathion and carbaryl quickly dissipated under aerobic conditions, with half-lives of only 0.8-4.9 d. Under anaerobic conditions, malathion degraded rapidly, with half-lives of 1.6-2.3 d. However, carbaryl became virtually non-degradable under anaerobic conditions, and its half-life increased to 125 d in San Diego Creek sediment and 746 d in Bonita Creek sediment. Persistence of diazinon was moderate, and its half-life (14-24 d) seemed to be unaffected by the redox conditions. Chlorpyrifos was moderately persistent under aerobic conditions, with half-life (20-24 d) similar to that of diazinon. However, significant increase in persistence also occurred with chlorpyrifos under anaerobic conditions, and its half-life was extended to 58-223 d. This study suggests that the persistence of OPs and carbamates in urban creek sediments varies greatly among compounds, and for the same compound, depends closely on the redox conditions. Prolonged persistence may occur under anaerobic conditions for the otherwise non-persistent compounds.
Key words: organophosphate and carbamate insecticides, degradation kinetic
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