Anthropogenic impact assessment of Niangziguan karst water

As the biggest karst spring system in northern China, the Niangziguan karst water system is the major source of water supply for Yangquan city, one of the most important bases of coal production in China. In this study, the chemical composition of karst groundwater was investigated with particular emphasis on identifying the sources of chemical variation. The results show significant geographic variation in chemical constituents through the karst groundwater system and also indicate that human activity is responsible for much of the observed hydrochemical variation. The addition of SO₄²⁻, Cl⁻ and NO₃⁻ from human activities causes the groundwater hydrochemistry to vary from the HCO₃-Ca-Mg or HCO₃-SO₄-Ca-Mg type to the SO₄-HCO₃-Ca, Cl-SO₄-HCO₃-Ca, SO₄-Ca or SO₄-Cl-Ca type. Results from factor analysis indicate that abnormally high levels of SO₄²⁻ and Na⁺ are from sources related to coal mining activity, which is widely distributed in the study area. High concentrations of Cl⁻ and NO₃⁻ result from sources related to human activities such as agriculture and mining wastewaters and sewage discharge. The results of cluster analysis in combination with hydrogeochemical analysis indicate that natural and anthropogenic processes jointly control the evolution of groundwater chemistry in regional groundwater systems like Niangziguan.