Statistical analyses of hydrochemistry in multi-aquifers of the Pansan coalmine, Huainan coalfield, China: implications for water-rock interaction and hydraulic connection

Kai Chen; Qimeng Liu; Tingting Yang; Qiding Ju; Yu Feng

doi:10.1016/j.heliyon.2022.e10690

Statistical analyses of hydrochemistry in multi-aquifers of the Pansan coalmine, Huainan coalfield, China: implications for water-rock interaction and hydraulic connection

Heliyon. 2022 Sep 20;8(9):e10690. doi: 10.1016/j.heliyon.2022.e10690. eCollection 2022 Sep.

Authors

Kai Chen^{1

2}, Qimeng Liu¹, Tingting Yang^{1

2}, Qiding Ju^{1

2}, Yu Feng¹

Affiliations

¹ School of Earth and Environment, Anhui University of Science & Technology, Huainan 232001, China.
² State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mine, Huainan 232001, China.

Abstract

Understanding the groundwater hydrogeochemical processes and aquifer hydraulic connections are essential for effective prevention of water inrush in concealed coal mines. In this study, 40 groundwater samples were collected from the loose layer aquifer (LA), coal measure aquifer (CA), and limestone aquifer (LA) in the Pansan coal mine, Huanan coalfield, China, and the major ion concentrations were analyzed by bivariate diagrams (Na⁺ + K⁺ - Cl^- versus Ca²⁺ + Mg²⁺ - SO₄ ^2- - HCO₃ ^- and CAI-I versus CAI-II), multivariate statistical methods, and receptor model in order to identify the water-rock interactions and aquifer hydraulic connections. Piper diagram showed that groundwater in LA and TA was dominated by the Na-Cl type, while groundwater in CA was mainly of the Na-HCO₃ type. Based on the results of bivariate diagrams and PCA/FA, weathering of silicate minerals and cation exchange (source 1), sulfate dissolution (source 2) and chloride dissolution (source 3) were the main processes controlling the groundwater chemistry. Unmix model revealed that the mean contribution of source 1 to CA samples was 74%, while LA and TA samples have higher contributions from evaporite dissolution (source 2 and source 3) relative to CA samples. Moreover, both clustering analysis methods (Q-type hierarchical and K-means cluster) confirmed the existence of a hydraulic connection between LA and TA in the northeastern part of the study area. It is concluded that the application of multivariate statistical analysis to interpret groundwater chemistry can provide useful guidance to prevent water inrush in coal mines.

Keywords: China; Hydrochemisty; K-means cluster analysis; Pansan coal mine; Receptor model; Water-rock interaction.