Transfer Characteristics Of Copper In Natural Sediment And Physicochemical Remediation On Contaminated Sediment

Sediments are the main fate of most pollutants in water. Heavy metal pollutants are accumulated in the sediments by precipitation, adsorption and so on, and under certain conditions, secondary pollution may occur if heavy metals are released from the sediments. So the sediment pollution control has been paid more and more attention by many countries.This paper was related to the project of Dongjiang water pollution control and governance, which belonged to the special programs concerning water pollution control and management of the Important National Science & Technology Specific Projects (2008ZX07211-004). The adsorption characteristics of copper on sediment and the effect of different components of sediment on adsorption were studied, the heavy metals immobilization was also studied in this paper.According to the stability under natural conditions of different components of sediment, we divided the sediment into three groups:Light Fraction (LF), Humic Substance (HS) and Heavy Fraction of Remove Humic Substances (HFRHS). The characteristics of copper adsorption on these three samples and the effect of different environment conditions on adsorption were both studied. The results showed that the adsorption rate of copper was controlled by LF and HS, while stabled HFRHS was the dominant component for copper adsorption. pH had a great influence on copper adsorption. Therefore, in natural environment, the transferability and environmental toxicity of copper could be reduced by controlling the migration and transformation of LF and HS.Site energy distribution model was used to analyze the different compounds of the sediment on the adsorption of copper in this paper, because of the heterogeneous surfaces of the sediment. At first, the samples were prepared by sequential extraction method, which is "in-situ" method. Using this method, five samples had been prepared by removing different compounds. Then the changes of sorption sites on samples were analyzed by site energy distribution model. The site energy distribution analysis showed that the sorption sites of iron/manganese hydrous oxides (IMHO) and organic matters (OM) have higher energy, but both them have a little effect on sorption energy because of the contents of them are small. The adsorption of copper on the main component-minerals in the sediments occurs in low energy area. There was a trend of the surface sorption sites of the sediments to change to homogenization after removing target components. Energy distribution model allows us to better understand some adsorption characteristics of sediment.According to the literature and the analysis of the experiments, Fly ash and fly ash+ humic acid mixture were chosen to fix Cu, Ni, Pb and Cd, and the immobilization effects were evaluated. Fly ash has good immobilization effects on Cu, Ni, Pb and Cd, and fly ash+humic acid mixture has better effects on Cu and Pb.