Assessment and Source Apportionment of Groundwater Pollution in Different Aquifers of the Taigemiao Mining Area, Xinjie, China

This study investigates the groundwater quality, spatial distribution, and pollution sources in the unexploited Xinjie Taigemiao mining area. A total of 25 groundwater samples were collected from different aquifers and analyzed using the entropy-weighted water quality index (EWQI), inverse distance weighting (IDW), and positive matrix factorization (PMF) model. The results showed that: (1) The Zhidan Group exhibited overall good water quality, with a mean EWQI of 59.02 and an excellence rate of 83.33%, making it suitable for direct drinking. In contrast, the Anding, Zhiluo, and Yan'an Groups displayed poor water quality, with mean EWQI values of 945.31, 466.67, and 800.82, respectively. All were classified as Class V, indicating extremely poor quality that is unsuitable for direct drinking or irrigation. Spatially, the EWQI of each aquifer exhibited distinct gradient characteristics: values for the Zhidan Group decreased from the eastern local pollution source to the periphery; for the Anding Group, values gradually decreased from southeast to northwest; for the Zhiluo Group, values decreased from high-pollution areas outward; and for the Yan'an Group, values decreased from northeast to southwest. (2) Shallow groundwater in the Zhidan Group is jointly influenced by natural geological background (contributing 58.0% of Na⁺ and 65.4% of Cl^-), hydrogeological activity (contributing 66.8% of TH), and anthropogenic activities (contributing 71.3% of NO₃ ^-). Pollution in the Anding Formation is dominated by natural geological background (contributing 88.5% of SO₄ ^2-) and anthropogenic activities (contributing 93.9% of COD). In contrast, the deeper Zhiluo and Yan'an Formations are mainly controlled by water-rock interaction (contributing 93.5% of Mn), redox-leaching processes (contributing 90.3% of Fe), and natural geological background (contributing 76.0% of Na⁺). Pollution sources differ significantly across aquifers, reflecting complex contamination characteristics. The findings of this study provide a scientific basis for safeguarding the health of residents near the mining area and ensuring drinking water safety.