Impact of Anthropogenic Activities on the Hydrochemistry of Subterranean Rivers in Bare Karst Area
Subterranean rivers are an important form of karst water in southwestern China,playing a significant role in local water sup-ply for humans and animals.However,subterranean river systems in bare karst areas are susceptible to human activities due to unique hydrogeological structures.Multiple research methods,such as the Hydrochemical Facials Evolution Diagram(HFE-D)and environ-mental isotope analysis,were applied to investigate the effects of human activities on the hydrochemistry of the subterranean river at Kaiyang.The results show that the dominant anions and cations in the groundwater were HCO3-and SO42-,Ca2+and Mg2+respectively,with the hydrochemical type being HCO3-Ca·Mg,mainly controlled by water-rock interaction.The SO42-,NO3-and Cl-in the subter-ranean river system is impacted by the activity from the southern county,landfill and slag yard.The HFE-D indicated that the down-stream section of the subterranean river was consistently affected by anthropogenic activities,and δ34S-SO42-isotopes suggest that sewage input accounts for the majority(71%)of the SO42-source,followed by atmospheric precipitation(22%).Isotope calculations for δ15N-NO3-and δ18O-NO3-indicate that NO3-is mainly sourced from sewage discharge(42%),atmospheric precipitation(37%),and agricul-tural inputs(21%).The openness of the bare karst subterranean river system hinders removal of nitrogen by denitrification.
bare karst underground riverhydrochemistryHFE-Denvironmental isotopesanthropogenic activities