Abstract: The chemical species of the Fe and Mn oxides in the natural surface coatings, which were developed in Xianghai Wetland, were investigated via Tessie r’s sequential extraction procedure. The results show that the Fe oxides exist mainly in Fe and Mn incorporated oxides form, while the Mn oxides primarily in organic form. The resulted information obtained also indicates that the chemical species of Fe and Mn oxides in the natural surface coatings may be important factors causing the difference between the adsorption capacity of Pb onto the Mn oxides and that of Cd onto the Fe oxides in the natural surface coatings.

Key words: natural surface coating, Fe and Mn oxides, chemical species, adsorptio n