Abstract:Biological accumulation and release of heavy metals in Ruditapes philippinarum have been observed in previous studies. However the specific process in individual tissues remained unclear. In this study, we used two-compartment bio-concentration model to evaluate the kinetic parameters of the biological accumulation and release of seven heavy metals (Pb, Zn, Cu, Cd, Cr, Hg, and As) in different tissues and organs of Ruditapes philippinarum, including visceral mass, gill, foot part and mantle tissues. In the experiments R. philippinarum was exposed to water containing all seven heavy metals. The uptake rate constant (k1), elimination rate constant (k2), bio-concentration factor (BCF), biological half-lives (B1/2), and equilibrium concentration in vivo (CAmax) of heavy metals were determined with non-linear curve fitting method. The results were summarized below: (1) Different heavy metals were accumulated with a preference in major organs and tissues of R. philippinarum. The CAmax of Cu, Cd, As and Pb in R. philippinarum followed the order: visceral mass > foot part > gill > mantle tissues; the CAmax of Cr: visceral mass > gill > foot part > mantle tissues; Hg (CAmax): foot part > mantle tissues > gill > visceral mass; Zn (CAmax): foot part > gill > mantle tissues > visceral mass. (2) BCFs of seven heavy metals in R. philippinarum were significantly different (P<0.05). Cu was the most accumulated heavy metal in R. philippinarum with a BCF range of 1514.0-4818.0, followed by Cd and Hg with a BCF range of 104.5-975.4 and 255.9-447.4, respectively. As, Cr, Pb and Zn were accumulated at a lower level with the BCF values below 300. The weakest accumulation was observed for As, and the BCF values in foot part, gill and mantle tissues were 56.0, 53.1, and 47.4 respectively. The BCF of Zn in visceral mass was 61.9. (3) After 25 days, concentrations of heavy metals in the major organs and tissues of R. philippinarum were still at high levels, which indicated R. philippinarum had weak ability to release heavy metals. Although the two-compartment kinetic model efficiently described the accumulation of heavy metals in R. philippinarum with most fitting indicators (R) above 0.9, it was not suitable for the simulation of the release phase, for example, the R values of Pb and Cu were only 0.110 and 0.230 respectively.
