Disappearance of endosulfan residues from seawater and sediment under laboratory conditions

The dissipation rate of endosulfan isomers (alpha and beta) in seawater and sediment was studied. The disappearance rate of both isomers from seawater and pure water was compared, and the same measurements were made in both s terile and unsterile marine sediment. Flasks of water and sediment, fortifi ed with a dispersion of a commercial endosulfan 350 g litre(-1) EC, Protoda n 35(R), were incubated under laboratory Light at room temperature for 82 d ays. A micro on-line extraction method and GC-ECD was used to determine the pesticide and its metabolites. The dissipation of endosulfan (in two phase s of first-order kinetics) occurred more rapidly in seawater than in pure w ater. At the end of the experiment, the concentration of alpha-endosulfan i n sterile sediment was four times greater than in unsterile sediment, while the dissipation rate of beta-endosulfan in unsterile sediment was approxim ately double that observed in sterile sediment. The dissipation of both for ms in sediment occurred in a single stage. Endosulfan beta-isomer was more persistent than alpha-isomer in both sterile and unsterile sediment. Dissip ation of endosulfan sum of alpha- and beta-isomers in sediment at the end o f the experiment ranged from 80% (sterile) to 95% (unsterile). Endosulfan s ulfate was detected in water and sediment as the main metabolite. (C) 2000 Society of Chemical Industry.