Hydrogeochemical characteristics, source identification and health risks of surface water and groundwater in mining and non-mining areas of Handan, China

摘要

The present work aimed to compare the effects of coal mining and agricultural land uses on the quality of surface water and groundwater in the Handan region in China. For this purpose, the natural water samples were collected from both a mining area and an area without mining in a similar geological setting. The results showed that the contents of total hardness (TH), NO3-, SO42-, Ca, K, Co, Se, Rb, Fe and Ni in groundwater of the mining area (MGW) were significantly higher (1.6-6.1 times) than those in non-mining area (AGW), exhibiting a decreasing trend with the increasing distance from the mining areas. Most elements in surface water from the mining areas (MSW) were higher (1.1-30.8 times) than the non-mining areas surface water (AGW). The medium and high-level pollution in mining area groundwater samples were 16.7% and 50%, while in non-mining area samples were 9.5% and 4.8%, respectively. The lithology of the aquifer [including coal and rock (Permian, Carboniferous, Triassic, Ordovician, and Quaternary)] and watercourses are the main controlling factor of the element variance in groundwater of the Handan area. The Fe and SO42- in the Handan water are derived from sulfide mineral oxidation and the evaporative concentration of sulfate in the aquifer, while the coal mining induced higher NO3- in the mining area (MGW) as compared to the non-mining area (AGW). Interestingly, several samples from the mining areas have met the requirement of Se-supplementation in the water (average=3.9 mu g/L), which is higher than the Hebei groundwater (0.8 mu g/L). The high Se in water is associated with the oxidation and leaching of selenium-rich coal and sedimentation of the coal ash. The concentration of Se, Sr, Rb, K, and NO3- generally show a large decline with the distance from mining areas, while Co, Ni and Ca trend are less clear. Unexpectedly, the elevated concentrations of chloride caused a non-carcinogenic risk for potable groundwater use in both the areas, while Pb caused a carcinogenic health risk in the mining areas. The spatial distribution of chemical constituents declines with the distance from mining areas. Noticeably, the elemental enriched coal-rock has caused the pollution of groundwater by rock weathering and percolation.