Hydrochemical Characteristics and Groundwater Source Identification of a Multiple Aquifer System in a Coal Mine

Abstract

Hydrochemical analysis and Bayesian discrimination were used to identify groundwater sources for multiple aquifers in the Panyi Coal Mine, Anhui, China. The results showed that the Cenozoic top aquifer water were HCO3−Na+K−Ca and HCO3−Na+K−Mg types, which distinguished it from the other aquifers due to its low Na+ + K+ and Cl− concentrations. The Cenozoic middle and Cenozoic bottom aquifer waters were mainly Cl−Na+K and SO4−Cl−Na+K types. The water types in the Permian fractured aquifer changed from Cl−Na+K to HCO3−Cl−Na+K and HCO3−Na+K moving away from the Panji anticline. In addition, HCO3 − concentrations increased and Ca2+ concentrations decreased with depth in the aquifer. The Taiyuan limestone aquifers were of Cl−Na+K, SO4·Cl−Na+K, and HCO3·Cl−Na+K types, and are very difficult to distinguish from the other aquifers. The precision of the Bayesian discrimination based on groundwater chemistry was 86.09%. Water chemistry indicators in the Permian fractured aquifer were moderately to highly variable and moderately to strongly correlated, spatially. The water chemistry spatial distribution indicates that the Permian fractured aquifer is recharged by the Cenozoic bottom aquifer near the Panji anticline, which reduces the accuracy of Bayesian discrimination in that area.