Origin and stability of pit lake water in Baiyinhua, Inner Mongolia, based on hydrochemistry and stable isotopes

ABSTRACT

Isotope technology is widely used in geochemical mechanisms analysis; however, studies on the origin of pit lake water by isotopes in coal concentration areas in grassland are rare. In this study, 20 groups of water samples were collected, which were subjected to chemical analysis to determine the hydrogeochemical characteristics of pit lake water. The mechanisms of pit lake water formation and recharge–evaporation were ascertained through principal component analysis and the Rayleigh fractionation model. The results indicate that the phreatic water is least affected by evaporation, followed by confined water, surface water and pit lake water. The ionic composition of surface water, phreatic water and most of the confined water is mainly affected by leaching, some confined water can be recharged by surface or phreatic water; while the ionic composition of pit lake water is dominantly affected by evaporation (69.4 %) and is less affected by groundwater recharge (17.1 %) and human activities (11.5 %). The pit lake water is recharged by precipitation, phreatic water and the lateral runoff of confined water; however, the proportion of phreatic and confined water recharge is small. The evaporative loss of the pit lake water is 40–61 % of the initial water body.

KEYWORDS:

• Evaporation
• hydrogen-2
• hydrochemistry
• Inner Mongolia
• isotope hydrology
• isotope fractionation
• open-pit coal mining
• oxygen-18
• pit lake water formation

Acknowledgments

The authors are very grateful for the help from the Key Laboratory of Mine Ecological Effects and System Restoration, Ministry of Natural Resources.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by the Project of China Geological Survey: Ecological geological survey of important mineral concentration area [grant number DD20230090], Innovation Project of Guangxi Graduate Education [grant number YCBZ202314].