BIOCONCENTRATION AND DEPURATION OF CHLORPYRIFOS IN THE MARINE MOLLUSKMYTILUS-EDULIS

The bioconcentration and depuration of chlorpyrifos [O,O-diethyl-O-(3, 5,6-trichloro-2-pyridil) phosphorothioate] for the marine mollusc Myti lus edulis was investigated under laboratory conditions in experimenta l aquaria. Renewal tests at concentrations of 1 and 3.2 mg/L followed by depuration tests were conducted. Organisms were exposed to pesticid e concentrations for 38 days and then were maintained in clean sea wat er until the chlorpyrifos were eliminated. Two different methods to es timate toxicokinetic rate constants of chlorpyrifos were compared, Tox icokinetic rate constants appeared to be dependent upon the level of e xposure, probably due to the toxic stress produced by the high exposur e 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 e stimated was similar to that calculated in the bioconcentration phase. The BCF obtained was lower than expected for K-ow of chlorpyrifos, su ggesting metabolic biotransformation of the parent pesticide.