Abstract: The selective separation of non-residual components of surficial sediments(surface coatings) was performed via chemical extraction techniques and then Cu and Zn adsorption to the non-residual components and residual component of surficial sediments(surface coatings) were investigated. The results indicate that 0.1 mol/L NH₂OH·HCl+0.1 mol/L HNO₃, (NH₄)₂C₂O₄-H₂C₂O₄ buffer solution and 30% H₂O₂ could remove Mn oxides, Fe/Mn oxides and organic materials from the non-residual components of surficial sediments(surface coatings) with the efficiency ranging from 63.15% to 97.59%, and the effects of extraction on non-target components were negligible. Cu adsorption to the surficial sediments(surface coatings) and the individual component of surficial sediments(surface coatings) were much greater than those of Zn, and the adsorption capability of surficial sediments was much smaller than that of surface coatings. Furthermore, Cu and Zn adsorption to the non-residual components of surficial sediments(surface coatings) were much greater than those to residual component, and that the greatest contribution to metals adsorption on a molar basis was from Mn oxides in the non-residual component. Metals adsorption capacities of Mn oxides exceeded those of organic materials by two orders of magnitude, and the estimated contribution of the residual component to metals adsorption was insignificant. These results imply that the role of surface coatings in transformation and cycling of heavy metals in aquatic environments was more important than that of surficial sediments, and the relative importance for controlling heavy metals in aquatic environments was attributed to metal(Fe and Mn) oxides.

Key words: Surficial sediment, Surface coating, Non-residual fraction, Selective extraction, Heavymetal, Adsorption