Hydrochemical characteristics and influencing factors of mine water in Tangjiahui mining area

Abstract

In water-deficient areas, the reuse of water discharged from coal mining is highly desirable. In order to study the water quality in the Tangjiahui mining area in Jungar Coalfield (Inner Mongolia, China), 34 groups of mine water samples collected at various stages during coal mining process were analyzed for their hydrochemical characteristics using conventional and statistical methods. A Piper trilinear diagram was used to analyze the main ion composition characteristics and the hydrochemical type of the mine water. Gibbs map and ion correlation methods were used to investigate the sources and influencing factors of the main ions in mine water. The results showed that the TH of the mine water in the study area was in the range of 219.52–390.6 mg/L with an average of 315.04 mg/L, which can be classified as slightly hard/ hard water. The TDS was in the range of 926.61–1889.56 mg/L with an average of 1514.31 mg/L, which mostly belongs to brackish water. The cation content in the mine water was ranked from the highest to the lowest as Na + > Ca 2+ > Mg 2+ , while the anion content was ranked as Cl − > HCO 3 − > SO 4 2− . The Na + mass concentration was in the range of 179.00–523.06 mg/L with an average of 399.77 mg/L, while the Cl − mass concentration was in the range of 207.10–812.63 mg/L with an average of 550.88 mg/L. The hydrochemical type of the mine water was Cl-Na. According to the correlation matrix of the various chemical indicators in the mine water, the TDS was significantly positively correlated with Na + , Ca 2+ , Cl − , and SO 4 2− . Of these, the main sources of TDS were Na + and Cl − , as these had correlation coefficients > 0.9. The hydrochemical characteristics of the mine water were mainly controlled by the condensation-crystallization and anti-cation exchange, which indicated the main ions were largely derived from the dissolution of halite . Due to its high TDS, EC,SAR, and Na% values, the mine water in the study area was not suitable for human consumption and agricultural irrigation. These results can provide a reference towards water resource management and the sustainable use of mine water by local governments.