Abstract
Hydrochemistry of groundwater is important in coal mines because it can be used for understanding water–rock interaction and inrush water source identification. In this study, major ion concentrations of groundwater samples from the loose layer aquifer (LA), coal-bearing aquifer (CA) and Taiyuan Formation limestone aquifer (TA) in the Qingdong coal mine, northern Anhui province, China, have been analyzed by a series of statistical methods for identifying the source of chemical constituents in groundwater and the source of inrush water. The results indicate that the mean concentration of the major ions in the LA were ordered as follows: HCO3− > SO42− > Na+ + K+ > Cl− > Ca2+ > Mg2+ > CO32−, whereas average values of the CA in decreasing order are SO42−, Na+ + K+, HCO3−, Cl−, Ca2+, Mg2+ and CO32−, and the major ion concentrations of the TA have the following order: SO42− > Na+ + K+ > Ca2+ > HCO3− > Cl− > Mg2+ > CO32−, and most of the samples are Na-SO4 and Ca-SO4 types. TDS content in water increases with aquifer depth, whereas the pH values ranged from 7.1 to 8.9, indicating a weak alkaline environment. Two sources (weathering of silicate minerals and dissolution of evaporate minerals) have been identified by principal component analysis responsible for the chemical variations of the groundwater, and their contribution ratios have been quantified by Unmix model. Moreover, based on the Q-mode cluster and discriminant analyses, the samples with known sources have been identified correctly to be 95.7% and 97.6%, respectively, and the samples with unknown sources have been determined with high probability (78–100%).
Highlights
Coal is a primary source of energy to China, and this situation will last for decades in the future
3 National Engineering Research Center of Coal Mine Water Hazard Controlling, Anhui 234000, China been attributed to be the complicated geological conditions, the imperfect mining technology or, the subjective neglect of the management. In response to this situation, two types of strategies have been applied for the prevention of water inrush in coalmines: (1) the active one, which means to predict the possibility of water inrush based on the understanding of the hydrogeological conditions of the coal mine; (2) the passive one, which means to do something to minimize the loss after the water inrush (Xu and Bu 2015)
Groundwater in the aquifers contains a series of information, including the water level, quantity, temperature, velocity, turbidity and hydrochemistry, among others (Gui and Chen 2007), which provides the possibility of the water source identification among different aquifers, and a large number of methods have been proposed (Liu et al 2018; Shi et al 2018; Wu et al 2019; Wang et al 2020)
Summary
Coal is a primary source of energy to China, and this situation will last for decades in the future. Previous studies revealed that five kinds of disasters (water, fire, gas, dust and roof) have brought to mankind, huge economic losses or the death of people (Wu et al 2013), and the reasons have In response to this situation, two types of strategies have been applied for the prevention of water inrush in coalmines: (1) the active one, which means to predict the possibility of water inrush based on the understanding of the hydrogeological conditions of the coal mine; (2) the passive one, which means to do something to minimize the loss after the water inrush (e.g., draining out of the water and recovering coal production) (Xu and Bu 2015). Understanding the hydrological condition of the coalmine before the water inrush is the most fundamental work for
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