Disappearance of endosulfan residues from seawater and sediment under laboratory conditions

The dissipation rate of endosulfan isomers (α and β) 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 sterile and unsterile marine sediment. Flasks of water and sediment, fortified with a dispersion of a commercial endosulfan 350 g litre−1 EC, Protodan 35®, were incubated under laboratory light at room temperature for 82 days. A micro on-line extraction method and GC-ECD was used to determine the pesticide and its metabolites. The dissipation of endosulfan (in two phases of first-order kinetics) occurred more rapidly in seawater than in pure water. At the end of the experiment, the concentration of α-endosulfan in sterile sediment was four times greater than in unsterile sediment, while the dissipation rate of β-endosulfan in unsterile sediment was approximately double that observed in sterile sediment. The dissipation of both forms in sediment occurred in a single stage. Endosulfan β-isomer was more persistent than α-isomer in both sterile and unsterile sediment. Dissipation of endosulfan sum of α- and β-isomers in sediment at the end of the experiment ranged from 80% (sterile) to 95% (unsterile). Endosulfan sulfate was detected in water and sediment as the main metabolite.