Accumulation, depuration and risk assessment of cadmium (Cd) and lead (Pb) in clam (Corbicula fluminea) (O. F. Müller, 1774) under laboratory conditions

The present study investigated the accumulation and depuration of two heavy metals Cd and Pb in the freshwater clam  (Corbicula fluminea) under laboratory conditions. Treated clams were exposed to single and combined treatments of Cd and Pb at the concentration of 5 mg L-1 and 10.5 mg L-1 for 10 days, respectively. The animals were then placed in metal free water for the following 5 days for depuration experiment. Heavy metal concentrations were determined by an inductively coupled plasma optical emission spectrometer (ICP OES).  Results showed that the clams were able to accumulate Cd and Pb at the maximum rate of 0.26 and 0.37 (µg g-1 day-1), respectively; and depurate at the rate of 0.32 and 0.08 (µg g-1 day-1), respectively. At the end of uptake period, the concentrations of Cd and Pb in the soft tissues of single and combined exposures were 1.8 and 1.1 µg g-1 wet  weights (WW) and 1.2 and 0.8 µg g-1 WW, respectively. The clams also showed rapid depuration of Cd and Pb. At the end of depuration, the concentrations of Cd and Pb in the soft tissues were only 0.2 and 0.8 µg g-1 WW in single and 0.17 and 0.4 µg g-1 WW in combined exposure, respectively. The results of the present study showed that there was a competition between Cd and Pb in the tissues of the clams. The total target hazard quotients and the hazard index indicated that people might experience adverse health effects through consuming contaminated C. fluminea.