Chemical characteristics of groundwater and surface water affected by human activities in the upper Jinzi River Basin, China

Water resources, as critical ecological and environmental assets, are essential to the social and economic development of countries and regions worldwide. The Jinzi River valley functions as a discharge area for industrial and domestic sewage from mining operations and residential communities along both banks. However, due to human activities, both groundwater and surface water in the region have been contaminated to varying extents. Multiple gold mines are located in the research area. Due to years of unregulated mining, this has had a serious impact on the local ecological environment and water quality. However, research on groundwater and surface water in this region, which are crucial components of the ecological environment, remains limited. This study integrates local socio-economic and hydrogeological conditions, employing methods such as multivariate statistical analysis, the Piper trilinear diagram, the Gibbs model, and ionic ratio relationships to analyze the characteristics and origins of major ions in the region. (1) The primary hydrochemical type of surface water was HCO₃-Ca·Na, while groundwater was predominantly of the HCO₃-Ca·Mg type. This hydrochemical pattern was consistent across the region, with ion concentrations significantly higher in areas dominated by carbonate rock compared to those with silicate rock. (2) Using principal component analysis, water-rock interaction modeling, and ion source analysis, it was determined that groundwater chemistry was primarily influenced by the weathering of diorite and carbonate rock, along with inputs from domestic and agricultural wastewater. In contrast, surface water chemistry was largely controlled by the weathering of carbonate rocks and the discharge of industrial wastewater. (3) Components such as SO₄^2-, NO₃^-, Cl^-, and total dissolved solids in surface water exhibited a pronounced sensitivity to human activities, with their concentrations significantly exceeding those in groundwater. This indicates that surface water is more heavily impacted by human activities, particularly from industrial, agricultural, and domestic wastewater sources.