Cadmium (Cd) and zinc (Zn) in surface water, sediment, carp, and crab samples collected from upstream and downstream regions of coastal watersheds along the Chinese Northern Bohai and Yellow Seas were analyzed to provide a comprehensive understanding and assessment of their environmental concentrations and bioaccumulations. The results showed that downstream waters contaminated with Zn would have adverse effects on aquatic organisms. Although nearly all sediments were contaminated with Cd due to human activities, little potential existed for Cd toxicity in sediment-dwelling fauna. Concentrations of Cd and Zn in most water, sediment, carp, and crab were less than published values. The downstream carp and crabs had higher mean bioaccumulation factors and biota-sediment accumulation factors for Cd but lower mean biota-sediment accumulation factors for Zn than the upstream carp and crabs. Based on the relationships among Cd and Zn concentrations in water, sediment, and biota, the authors conclude that Cd and Zn in crabs primarily derived from sediment exposure. Although Cd and Zn in water and sediment originated from some of the same sources, the sources of Cd or Zn in water were likely different from those in sediment.
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