Water rock interaction in deep groundwater aquifers of coal mining area: qualitative and quantitative approaches based on hydrochemistry

Abstract

Present study indicates that groundwater from three aquifer systems have different concentrations of major ions. This implies that kinds and degrees of water rock interactions in them are different with each other. Relationships between major ions or their ratios (e.g. Gibbs diagrams, Na⁺-Cl^- relationships), as well as statistical analyses (correlation and factor analyses) suggested that water rock interaction is the main mechanism controlling the groundwater chemistry. EPA Unmix model has identified two sources responsible for the hydrochemistry of the groundwater, sulfate-carbonate (source 1) and silicate-chloride (source 2) sources. Groundwater from the limestone and coal bearing sandstone aquifer systems are mainly contributed by source 1 and 2, respectively. As to the groundwater from the loose layer aquifer system, the contributions of the source 1 and 2 are 4: 6, respectively, and the result is consistent with previous exploitation.