Groundwater Hydrogeochemical Mechanisms and the Connectivity of Multilayer Aquifers in a Coal Mining Region

Abstract

Multiple runoff connections for groundwater supply and water quality evolution mechanisms were disclosed using hydrochemistry, multivariate statistics, stable hydrogen and oxygen isotopes, and inverse hydrogeochemical modeling in a multi-layer groundwater system in a north China coal-mining district. Groundwater quality was mainly influenced by dissolution and weathering of carbonate, silicate, gypsum, halite, and fluorite, as well as cation exchange. Sulfate enrichment in the Carboniferous limestone aquifer may be due to pyrite oxidation, while gypsum dissolution and sewage contribute sulfate to the Quaternary alluvium. The Ordovician limestone groundwater is hydraulically connected to the other two aquifers. Incongruent dissolution of dolomite occurs when the Ordovician limestone water contacts the Carboniferous aquifer, while evaporation occurs when the Ordovician limestone water migrates upward through fractures to the Quaternary aquifer.