[Bioavailability of cadmium associated with oxides in sediment: effects of species of mineral, association form and aging on bioavailability].

The bioavailability of heavy metals in sediments is largely controlled by their speciation. Effects of different Cd speciation associated with metal hydroxide on Cd bioavailability were studied. Iron and aluminum hydroxides were chosen as representatives of the oxides commonly present in sediments. In cultivar system, Hoagland solution was used as nutrition supply, and metal hydroxide associated with Cd as the only source of contamination and Phragmites australis was induced to study Cd bioaccumulation. After 13 d cultivation, Cd was uptaken and accumulated in P. australis, with different bioaccumulation from 9.1 to 37.8 mg x kg(-1) in root; and 0 to 10.0 mg x kg(-1) in shoot. Hereinto, the P. australis cultivated in Fe0.5Al0.5(OH)3 medium was found to have accumulated the largest amount of Cd in root, followed by those in Fe(OH)3 and aged Fe0.5Al0.5(OH)3, the lowest root concentration of Cd was observed in the plants cultivated in aged Fe(OH)3. Desorption order of Cd by organic acid was consistent with the Cd accumulation in P. australis. Thus, coprecipitation treatment decreases the bioavailability of Cd; association of aluminum hydroxide with Cd is poor due to its physicochemical property; aging treatment significantly restrict the accumulation of adsorbed Cd; desorption by organic acid verify the discrepancy in bioavailability of different speciation of Cd.