Hydrochemical characteristics and source analysis of mine water in shallow coal seams in Shaanxi and Inner Mongolia contiguous area

In order to study the hydrochemical characteristics and sources of mine water under the mining of shallow coal seams in the contiguous area of Inner Mongolia and Shaanxi, the hydrochemical characteristics and the formation action of mine water in this area were investigated through the study of hydrochemical characteristics, mathematical statistics, ion ratio coefficient method and the hydrogen and oxygen isotopes in combination, by collecting samples of the mine water, groundwater in different aquifers and surface water in the study area. Based on this, the main sources of mine water in the study area were identified. The results show that the mine water is closely related to the groundwater hydraulics of Quaternary Salawusu Formation, Jurassic Zhiluo Formation and Yan'an Formation. Besides, the formation of main ions in mine water is affected by water-rock interaction, with the main anion and cation coming from the leaching of silicate minerals and calcite. Affected by reverse cation exchange, the content of Na⁺ in mine water is higher than that in the shallow groundwater. However, mixing has little effect on the formation of hydrochemical composition of mine water. The mine water is recharged by the groundwater of Yan'an formation, Zhiluo formation and Salawusu formation, accounting for 86.39%, 1.59% and 12.02% respectively in the recharging water sources. The research results could provide a basis for water hazard prevention and control of mine, as well as the treatment and utilization of water resources in this area.