| Heavy metals, which can do great harm to the environment and human being health due to their nonbiodegradable properties, bioaccumulation effects, and toxicities even at low concentrations, have prompted great interests. The speciation and transformation of heavy metals in the aquatic environments are affected significantly by the solid phases in the water, and reactions occurring at solid surfaces play dominant roles in determining metal partitioning between the solid and solution phases, and thus, the potential impact of metals in the aqueous environments.In the natural water, solid surfaces are usually covered with kinds of composite solid things, which consist of ferromanganese oxides, microorganisms, natural organic matters and many other things. These solid things play important roles in the interfacial reactions and compose what we call surface coatings. Due to the high surface reactivity and large surface areas, the most important role of surface coatings in the aquatic environments is to adsorb or enrich pollutants in the water. Besides, the adsorbed pollutants may be degraded or detoxified due to the bioactivity of microorganisms. Studies on surface coatings developed in natural waters have shown that ferromanganese oxides and organic matters are the most important components in the contributions of Pb and Cd adsorption to surfaces coatings. While there may be great differences in the adsorption characteristics, contents of components, and structures of surface coatings between those developed on the got-up matrix and those sampled directly from natural matrix such as rocks due to the limit of the season and the time which are needed for the development of natural surface coatings. What's more, compared to the developed surface coatings, the structures of microorganisms in the directly sampled surface coatings are more compatible with the natural waters. Researches concerning about heavy metals adsorption to natural surface coatings sampled directly from natural matrix and their components will reveal in good sooth the behavior of heavy metals in aquatic environments, do great help to the understanding of the mechanisms of their removal, and will also be hopeful to the development of aquatic environmental chemistry practicably and theoretically. To see about the relative contributions of components of surface coatings to the adsorption of heavy metals, it is very essential to separate the principle components of surface coatings and then investigate the contributions of every part to the adsorption. In this research, the proper extracting reagents and the optimum extracting conditions were selected and optimized based on previous research, and the thermodynamic characteristics of Pb and Cd adsorption to natural surface coatings and their components were studied.The location for sampling surface coatings was on the upriver of Songhua River, where the Linjiangmen Bridge is located, in Jilin, Jilin Province. The cobblestones covered with surface coatings near the bank were taken out of the water, and the surface coatings were scratched by plastic apparatus, transferred into plastic bottles filled with Minimal Mineral Salts (MMS), and taken back to the lab as quickly as possible.Before use, the surface coatings were filtrated and rinsed by MMS to remove the impurities. The organic materials of the surface coatings were qualified by measuring chemical oxygen demand (COD) using a standard method. The total contents of metal (Fe, Mn) oxides were analyzed by FAAS after extracted by 15% HNO3 for 24 h.The contents of iron oxides and manganese oxides are 266.80 ± 11.272 μmol Fe/g and 19.35 ± 0.69 μmol Mn/g, respectively, and the value of COD standing for the weight of organic materials is 98.08 ± 5.28 mg COD/g. Obviously, COD and the total iron oxides are relatively high. The ratio of contents between iron oxides and manganese oxides is, which is close to that of surface coatings sampled from Xianghai Wetland, distinctly higher than that developed in natural waters.In this study, NH...
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