KINETIC STUDY ON THE BIOCONCENTRATION OF Cu AND Pb IN TWO KINDS OF MARINE BIVALVE MOLLUSCS UNDER THE CONDITION OF SEDIMENT EXPOSURE

The kinetic parameters of the absorption process on accumulation and elimination of heavy metals Cu and Pb in Meretrix meretrix and Sinonovacula constricta were investigated under the condition of sediment exposure based on an established water-sediment-organism system. The kinetic parameters of bioconcentration were obtained by nonlinear curve fitting from the semi-static two-compartment model, including uptake rate constant (K1), elimination rate constant (K2), bioconcentration factor (BCF), and biological half-life (B1/2). The modeling results showed that K1 ranged from 4.63 to 69.41, K2 ranged from 0.05 to 0.08, CAmax ranged from 9.83 to 40.57, BCF ranged from 60.77 to 1444.56, B1/2 ranged from 9.09 to 14.43 in M. meretrix, K1 ranged from 4.27 to 122.92, K2 ranged from 0.05 to 0.07, CAmax ranged from 5.12 to 32.84, BCF ranged from 65.68 to 2112.02 and B1/2 ranged from 9.81 to 14.15 in S. constricta, respectively. It was found that the metal concentration were fitted to the two-compartment model, and good agreement was found between the predicted and observed metal concentrations using the goodness-of-fit test under the condition of sediment exposure. The results also indicated that the uptake rate constant (K1) and bioconcentration factor (BCF) of M. meretrix and S. constricta generally decreased with the increase of heavy metal exposure concentration in ambient seawater, and so as the CAmax, the bioaccumulation ability order for the two heavy metals was Cu>Pb, the biological half-life (B1/2) of Cu was longer than those of Pb, the maximal content in the organism (CAmax) at the theoretic equilibrium increased and was basically and directly proportional to increasing metal concentration in the outside water. The experimental results showed that the semi-static two-compartment kinetic model could well fit the bioconcentration of heavy metals Cu and Pb in M. meretrix and S. constricta, but required further experimental research and analysis under different conditions.