The Origin and Stability of Pit Lake Water in Baiyinhua, Inner Mongolia, based on Hydrochemistry and Stable Isotopes (δD, δ18O)

Abstract

Abstract The Baiyinhua area of Inner Mongolia is rich in coal resources but lacks water resources. Water required for ecological restoration in mining area is primarily obtained via pit lake water recycling. However, robust data has not yet been obtained to characterize the nature of the source, evaporation, and supply of the pit lake water. In this study, 20 groups of different water samples in the Baiyinhua mining area were collected, which were subjected to chemical analysis to determine the contents of hydrogen and oxygen stable isotopes (δD, δ18O) and ion ratios. By principal component analysis and the Rayleigh fractionation model, the mechanisms of pit lake water formation and the extent of its evaporation in the Baiyinhua mining area were revealed. The results show that the hydrochemical type of the pit lake water in the Baiyinhua mining area of Inner Mongolia is the HCO3-SO4-Na type, which is different from the surrounding water bodies (HCO3-Na-Ca and Cl-HCO3-Na types). The formation of pit lake water is mainly affected by evaporation (69.42%) and is less affected by groundwater recharge (17.06%) and human activities (11.51%). Due to its open area and relatively closed system, the evaporative loss of the pit lake water is relatively large, at about 40%-61% of the initial water body, which is 1%-22% higher compared to a nearby natural water body.