Bioaccumulation of cadmium bound to ferric hydroxide and particulate organic matter by the bivalve M. meretrix

Ferric hydroxide and particulate organic matter are important pools of trace metals in sediments and control their accumulation by benthic animals. We investigated bioaccumulation of cadmium in bivalve Meretrix meretrix by using a simplified system of laboratory synthesized iron oxides and commercially obtained humic acids to represent the inorganic and organic matrix found in nature. The results showed that bioaccumulation characteristics were distinctly different for these two substrates. Bioaccumulation from ferric hydroxide was not observed at 70 and 140 mg/kg, while the clams started to absorb Cd at 140 mg/kg from organic matter and the bioaccumulation rate was faster than that from ferric hydroxide. Within 28 d, accumulation of Cd from organic matter appeared to reach a steady state after rising to a certain level, while absorption from ferric hydroxide appeared to follow a linear profile. The findings have implications about the assimilation of trace metals from sediments by benthic animals.

► Accumulation of Cd adsorbed on ferric hydroxide and particulate organics was studied.
► Bioaccumulation characteristics were distinctly different for the substrates.
► The result was attributed to different properties and bio-responses of the particles.
► Bivalves may not accumulate more metals associated with more bioavailable particles.