Bioconcentration and Depuration of Chlorpyrifos in the Marine Mollusc Mytilus edulis

Abstract.

The bioconcentration and depuration of chlorpyrifos [O,O-diethyl-O-(3,5,6-trichloro-2-pyridil) phosphorothioate] for the marine mollusc Mytilus edulis was investigated under laboratory conditions in experimental aquaria. Renewal tests at concentrations of 1 and 3.2 mg/L followed by depuration tests were conducted. Organisms were exposed to pesticide concentrations for 38 days and then were maintained in clean sea water until the chlorpyrifos were eliminated.

Two different methods to estimate toxicokinetic rate constants of chlorpyrifos were compared. Toxicokinetic rate constants appeared to be dependent upon the level of exposure, probably due to the toxic stress produced by the high exposure level assayed. Lipid based Bioconcentration Factor (BCF) calculated by first order kinetic fit was found to be 482 ± 86. The depuration of chlorpyrifos by mussels maintained in clean sea water was fitted to first order one-compartment model, and the depuration rate constant estimated was similar to that calculated in the bioconcentration phase. The BCF obtained was lower than expected for K _ow of chlorpyrifos, suggesting metabolic biotransformation of the parent pesticide.