| Abstrakt: |
China as a biggest producer of electrolytic manganese is in the imperative to ameliorate the soil pollution which caused by electrolytic manganese waste residue. In this study, a survey was undertaken at a electrolytic manganese residue storage in Caixi Village of the Yuping Dong-minority Autonomous County under the jurisdiction of Tongren City of Guizhou Province, where the largest reserve of manganese ore resources in China is situated. To understand the characteristics of soil pollution, the speciation distribution of heavy metals (incl. Mn, Zn, Pb, Ni, Cr and Cd), and ecological risk of heavy metal contamination of the soil around the electrolytic manganese residue storage were analyzed by wet digestion and BCR sequential extraction. Mn, Pb and Cd, inter alia, had caused the severest impacts on the environmental quality of soil: Mn concentration was in the range of 356~14 915 mg/kg, with an average of 3 828 mg/kg, being 4.8 times higher than the background value of the soil in Guizhou; and the average concentrations of Pb and Cd were 3.1 and 40.2 times, respectively, higher than the "risk screening values of the National Standard for Farmland Soil". As to the heavy metal speciation, six species of heavy- metal were mainly composed of migratory dissolved weak acid, and the content of dissolved fraction of weak acid of Mn and Cd in soil increased as the distance got closer towards the residue storage dam (P<0.05). According to the analytic result by using the common Kriging spatial interpolation, there existed a kind of moderate spatial correlation among the content of Mn, Cd, Zn, Pb and Ni; in addition, the content of Mn and Cd, among others, were randomly affected by the pollution of human activity considerably; and the spatial distribution of concentrations of Mn and Cd in general showed the higher in the east and lower in the west parts of the area being investigated, and the high values of Mn and Cd concentrations were found mostly near the dam of the waste residue storage; and the results of principal component analysis (PCA) indicated that Mn, Cd and Pb were mainly resulted from the pollution of electrolytic manganese residue, while the contamination sources of Ni and Zn could be traced to the nearby agricultural activities and industrial production. Furthermore, Cr was mainly affected by the geological background factors, the highest potential ecological risk level belonged to the soils in proximity to the waste residue storage, and particularly, the contribution ratio of Cd was the highest (91%). [ABSTRACT FROM AUTHOR] |
