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Soil pollution in coal mining areas is a serious environmental problem in China and elsewhere. In this study, surface and vertical profile soil samples were collected from a coal mine area in Dazhu, Southwestern China. Microscopic observation, concentrations, chemical speciation, statistical analysis, spatial distribution, and risk assessment were used to assess heavy metal pollution. The results show that the weathering of coal-bearing sandstone and mining activities substantially contributed to soil pollution. The concentrations of Fe, Ni, Cu, Zn, Mn, Cd, Hg, and Pb exceeded their background values. Cd caused the most intense pollution and was associated with heavily–extremely contaminated soils. The residual fraction was dominant for most metals, except Cd and Mn, for which the reducible fraction was dominant (Cd: 55.17%; Mn: 81.16%). Zn, Ni, Cd, and Cu presented similar distribution patterns, and Hg and As also shared similar distribution characteristics. Factor 1 represented anthropogenic and lithologic sources, which were affected by mining activities; Factor 2 represented anthropogenic sources, e.g., fertilizers and traffic pollution; and Factor 3 represented the contribution of metals from soil-forming parent material. More than half of the study area had high pollution risk and was not suitable for vegetable cultivation.

Coal mine pollution has become one of the most serious environmental problems in China and elsewhere. Water, in the form of groundwater and streams, as well as stream sediment samples, were collected from the coal mine area in Dazhu, Southwestern China. Different analyses, including the hydro-geochemical, multivariate analyses and X-ray analyses, were conducted to examine the coal mine pollution effect. The study results show that the groundwater and stream samples are slightly acidic to alkaline with pH values of 6.36 to 7.17 and 6.51 to 7.39, respectively. With the dissolution of carbonate and sulfate, a large amount of Ca2+, Mg2+, and SO42- is found in the groundwater and stream samples, which is higher than the environmental background value. Typically, the water samples are dominated by Ca2++Mg2+-HCO3- and Ca2++Mg2+-Cl-. According to Chinese standard and the World Health Organization’s guidelines, the water in the coal mine area is of good quality in terms of its physical and chemical properties, except for the concentrations of Fe and Mn (1925.14 and 12872.882 μg/L, respectively). Principal component analysis reveal two groups that explained the variance in the data consisting of SO42−, Ca2+, Mg2+, and low pH as well as HCO3−, Na+, and Cl−, which can reflect the acid mine drainage effects as well as different human activities or the evaporation found in low mountains and hills, respectively. Hence, the concentrations of metals and metalloids in the stream sediments are affected by the coal mine drainage, which are generally enriched in Cr, Mn, Zn, Sr, Co, Ni, Cu, Al, Ca, Fe, and Mg. Mn and Fe average concentrations are higher in the downstream Kongjiagou drain stream sediment samples were 2035.03 ppm and 6%, respectively, relative to the Mn and Fe average concentrations in Xiaojiagou of 453.04 ppm and 2.96%, respectively. Both Mn and Fe concentrations are higher than the background values. Ultimately, mine closures can help with the process of ecological and environmental recovery.

In this study, groundwater, stream water, and stream sediment samples were collected from a coal mine area in Dazhu, Southwestern China, and hydrogeochemical, multivariate, and X-ray analyses were conducted to examine the effects of coal mine pollution. The groundwater and stream samples were slightly acidic to alkaline (6.7 to 8.2). Typically, the water samples were dominated by Ca2+ + Mg2+–HCO3− and Ca2+ + Mg2+–Cl−. SO42− originates from gypsum dissolution and pyrite oxidation, and Ca2+ and Mg2+ may be related to the dissolution of carbonate. According to the Chinese standard and World Health Organization guidelines, the water in the coal mine area is of good quality in terms of its physical and chemical properties, except for the concentration of Mn and Fe, with values of 1925.14 μg/L and 12,872.88 μg/L, respectively. A principal component analysis revealed two groups in which the concentration of metals and metalloids in stream sediments are affected by the coal mine drainage. The Mn and Fe average concentration in the downstream Kongjiagou drain sediment samples was 2035.1 ppm and 6%, respectively. These values were higher than the average Mn and Fe concentration in Xiaojiagou at 453.1 ppm and 2.9%, respectively. Both the Mn and Fe concentration were higher than the background values (640 ppm and 4.4%).