Meitan xuebao (Sep 2024)
Research progress and prospects on the water quality evolution of closed coal mine water in China
Abstract
With the gradual increase in the number of closed coal mines in China, the deterioration and pollution of water quality in closed coal mines are becoming increasingly prominent. Accurately understanding the evolution laws and mechanisms of water quality in closed coal mines is a major scientific challenge for the sustainable and green development of closed coal mines, as well as an important prerequisite for effective prevention and control of groundwater pollution and rational development and utilization of water resources. Based on the review of the development history of closed coal mines, this paper first elaborated on the distribution of closed coal mines in China. Then, a review was conducted on the water quality characteristics, water quality evolution laws, and the multiple field effects of water quality evolution of closed mine water in China. Finally, the key issues and application directions in the research of closed mine water quality in China were prospected. The research results indicate that: ① as of the end of 2023, the number of closed coal mines in China has increased to 130 00, mainly distributed in the areas such as Shanxi, Henan, Hebei, Shandong, Jiangsu, and northern Anhui. ② The pH, mineralization degree, sulfate, fluoride, and iron manganese heavy metal content of some closed mine water in China exceed the Class III water standard. Among them, the acidic mine water (pH 1 000 mg/L) is mainly distributed in Luxi, Shanxi, Henan, Huaihe, Inner Mongolia, Ningdong, Xinjiang and other regions; the sulfate mine water (sulfate concentration > 250 mg/L) is mainly distributed in Yungui, Luxi, Shanxi, Inner Mongolia, Ningdong, Shendong, Xinjiang Hami and other regions; the fluoride mine water (F content > 1.0 mg/L) is mainly distributed in the Huaihe River, Shanxi, Shendong and other regions; and the iron and manganese heavy metal mine water (Fe content > 0.3 mg/L, Mn content > 0.1 mg/L) is mainly distributed in Yungui, Luxi, Shanxi, Inner Mongolia and other regions. ③ Before the mine is completely submerged, there is a clear stratification phenomenon in the water quality of the mine water in space, namely the high-quality water layer in the shallow part, the transitional water layer in the middle part, and the low-quality water layer in the deep part, which is mainly related to the factors such as the spatial distribution of mining, geothermal gradient, and salinity. ④ After the closure of the coal mines, the evolution process of mine water quality can be roughly divided into three stages. The first stage is that the concentration of typical pollutants (sulfate and iron ions) in the closed mine water rapidly increases and reaches its peak, the second stage is that the concentration of pollutants rapidly decreases, and the third stage is that the closed mine water quality is the same as the background value of groundwater quality in adjacent aquifers and remains relatively stable. ⑤ The research progress on the chemical field, hydrodynamic field, microbial field, and temperature field of closed mine water in China is systematically summarized, and it is pointed out that the research on the coupling mechanism of multiphase (water-rock-gas generation) and multi-field (hydrochemical field-hydrodynamic field-microbial field-temperature field) in closed mine water is still insufficient. ⑥ It is pointed out that the research on the water quality evolution of closed mine water in China still faces some key scientific issues such as unclear water quality evolution laws and mechanisms.
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