Cu and Zn adsorption onto non-residual and residual components in the natural surface coatings samples (NSCSs) in the Songhua River, China

Natural surface coatings samples (NSCSs) from the surface of river shingles were employed to investigate the roles of non-residual and residual components of the NSCSs in controlling Cu and Zn adsorption via the selective extraction techniques and statistical analysis. The results indicate that the greatest contribution to metals adsorption on a molar basis was from Mn oxides in the non-residual fraction. Metals adsorption capacities of Mn oxides exceeded those of Fe oxides by one order of magnitude, fewer roles were found attributing to adsorption by organic materials (OM), and the estimated contribution of the residual fraction to metals adsorption was insignificant. These results implied that Mn oxides were the most important component in controlling heavy metals in aquatic environments. Experiments with Cu and Zn adsorption measured together showed that Cu severely interfered with Zn adsorption to the NSCSs and vice versa under the conditions of the two coexisted ions adsorption.