Species and tissue-specific bioaccumulation and risk assessment patterns of heavy metals in bivalves from northern China

Bivalves play a crucial role in marine biogeochemical cycles and are highly sensitive to heavy metals (HMs) due to their filter-feeding behavior, making them widely recognized as bioindicators and an important human exposure pathway for these contaminants. This study employed several models to explore the species- and tissue-specific capacity for HM accumulation in bivalves and to assess the ecological risks in the environment and the health risks to humans. The results revealed significant differences in HM bioaccumulation and health risks among species. Oysters demonstrated a higher potential for HM bioaccumulation than other bivalve species. Additionally, oysters and scallops preferentially accumulated Cd, while clams and mussels accumulated As. The health risks associated with ingesting these four bivalve species were acceptable. However, Cu and Zn were found to have minimal effects on health risks and should not be prioritized in risk assessments. Two-way ANOVA results indicated that the concentrations of As, Cr, Ni, Hg, and Pb in bivalves were primarily influenced by tissues. In addition, a similar accumulation effect was observed between the muscle and visceral mass tissues by SEM, suggesting that muscle tissue may be a more reliable indicator for health risk assessments than the more complex visceral mass. Furthermore, the Monte Carlo simulation indicated that health risks to humans from ingesting bivalves exposed to HMs were non-negligible. These findings provide novel insights into the species- and tissue-specific dynamics of HM pollution in bivalves and highlight the need for further control of HM pollution in bay ecosystems.