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.

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%).