Natural and anthropogenic factors influencing hydrochemical characteristics and heavy metals in groundwater surrounding a gold mine, Thailand

摘要

This study focused on groundwater quality around a gold mine at the border between the Phichit and Phetchabun provinces by investigating hydrogeological and hydrochemical characteristics and performing a multivariate analysis to determine the impact of natural and anthropogenic processes on groundwater quality. Groundwater samples were collected from 47 wells in the summer and rainy seasons, and hydrochemical parameters were measured on-site and analyzed in a laboratory. The hydrogeologic characteristics of the study area can be categorized into Quaternary floodplain deposits (Qfd), terrace deposits (Qt), weathered fractures volcanic rocks (Vw), volcanic rocks (Vf), and massive volcanic rocks (Vm). According to the Piper Diagram, water types in the summer season are Ca-Na-HCO3 (34.29%), Ca-HCO3 (22.86%), and Na-HCO3 (22.86%), whereas the rainy season primarily features Na-HCO3 (44.74%), and Ca-Na-HCO3 (39.47%). The principal component analysis (PCA) produced seven significant components that explained 71.50% of the cumulative variance. We divide primary contributors to groundwater into two groups. PC1?PC5 (from natural processes) include Na+, K+, Ca2+, and Al (mineral components of potassium feldspar and plagioclase feldspar), Fe, Zn2+, Pb2+, Cu2+, Co2+, and Mn2+ (associated minerals, such as sphalerite (ZnS), galena (PbS), chalcopyrite (CuFeS2), and pyrite (FeS2)), and inclusions in gold ore (low sulfidation epithermal gold deposits). The second source, PC6 and PC7 (mainly from human activities), includes NO3?, and, PO43? from fertilizers in agricultural areas and wastewater discharge from residential areas. This study revealed that natural and anthropogenic processes affected the hydrochemistry of groundwater, but natural processes played a greater role.