[Bioavailability of adsorbed Cd on typical oxides of sediment in Phragmites australis]

Effects of different chemical speciation (e.g. adsorbed on different metal oxides) in environment on Cd bioavailability were studied. Goethite, magnetite, gibbsite, alumina, and manganese oxide were chosen as representatives of oxides commonly present in sediment. In cultivar system, Hoagland solution was used as nutrition supply, and single metal oxide adsorbed Cd as the only source of contamination and Phragmites australis was induced to study Cd bioaccumulation. After 45-day cultivation, Cd was uptake and accumulated in P. australis, with different bioaccumulation from 72.70 mg x kg(-1) to 320.44 mg x kg(-1) which in root followed degressive order: Al(OH)3 > Al203 > Fe3O4 > MnO2 > FeOOH. Acetic acid, malic acid and citric acid were used to demonstrate the variation of desorption of Cd from different oxides which indicated the adsorption ability and stability. Desorption of Cd by acetic acid and malic acid followed the descending order: Al(OH)3 > Fe3O4 > Al2O3 > FeOOH > MnO2; by citric acid was Al(OH)3 > Al2O3 > Fe3O4 > FeOOH > MnO2, which was consistent with the Cd accumulation in root. The chemical speciation was the main factor to affect the bioavailability of Cd.