| Waste rocks produced by mining, are always enriched with pyrite and other sulfides. The oxidation and decomposing of the sulfides may cause the production of acid mine drainage (AMD), and the dispersion of heavy metals. That may take impacts to the environments. With the rapid growth of population and economic development, mineral resources are of great necessarity for human beings. The pollution problems of solid wastes produced by mining are becoming more and more serious, and the relative environmental geochemistry study is being of a hot talk in recently years.Based on literatures and field investigation, the Xiangtaoyuan waste dumps at the Taojiang Mn-ore deposit in central Hunan was selected for this study. The waste rocks of different weathered degrees, the relative soils, and the waters distributed throughout the ming area were sampled during field work in July 2005. Major elements, heavy metals, trace elements and rare-earth elements (REE) of all the samples were analyzed in laboratory using ICP-MS technique. The results were geochemical studied using mass balance principles and other methods, and then the heavy metal contaminations developed on soils and surface waters were evoluted based on understanding the mobility and transformation of all the elements during waste rocks weathering. The quality of soils and surface water of the mining area was assessed based on data of ICP-MS analyzing. The possible relation of heavy metal contamination of soils and surface water to the waste rock pile was investigated. Based on our above investigation, research and discussion, we can offer some information about the study as follows:(1) Observing in the field and the analytic results indicate that: the black shales and rhodochrosite ores make up the main materials of the waste rock dump. The waste rocks were weathering and decomposing during supergene geochemical condition.(2) Waste rocks from selected profile and light weathered waste rocks show similar normalized REE pattern of right-inclined curve as same as wall-rock. The contents of Sc, Ti, Cr, Ga, Ge, Rb, Y, Cs, Hf, Ta, Nb, Th, and REE were considerable in the waste rocks. However, concentrations of V, Mn, Co, Ni, Cu, Zn, Ba, Pb, and U vary in a large range. The higher averaging contents in the waste rocks from selected profile, it indicated that the longer weathering period, the higher contents of heavy metals in the waste rocks.(3) The weathered rhodochrosite ores were differing from other waste rocks in the geochemistry of REE, trace elements and heavy metals.(4) Based on the mass-balance calculation of waste rocks, we conclude that: Sc, V, and Cr were released from waste rocks from selected profile, especially for V. In the profile, most of elements were more activity in the first and third layers but enriched in the downmost two layers. Heavy metals, such as Sc, V, Cr, Co, Ni, Cu, Zn, Pb, Th, U, and Cd were released distinctly in the light waste rocks, and V, Zn, U, Cd for the most.(5) The concentration of heavy metals in the soils increase gradually by getting closer to the mining area. Using the Igeo index and potential ecological risk index assess heavy metals contamination. Both of the results suggested that soils under waste dumps were suffered the most serious contamination, and Mn, Co, Cu, Pb, and Cd show the most heavy contamination and ecological risk.(6) The mine drainage samples show the most obvious contamination, Fe, Mn, Ni, T1 exceed the Nationalâ…¡Class Groundwater Standard, and the underground water was uncontaminated.(7) According to the total contents of heavy metals containing in the waste rocks, we can conclude that waste rock pile have imposed potential harm on surrounding environment. Co, Ni, Cu, Zn, Cd and other heavy metals showing more mobility in the waste rocks, are apparently enriched in soils and water of the mining area. By the change of environmental condition and increasing effect of waste rocks weathering, all above mentioned contamination will become stronger. On the other hand, the negative impact on the ecosystem are mainly surrounding the waste dump, due to most of the heavy metal were not released from waste rocks from selected profile.
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