裸露型岩溶区人类活动输入对地下河水化学的影响

Impact of Anthropogenic Activities on the Hydrochemistry of Subterranean Rivers in Bare Karst Area

地下河是西南岩溶水的重要赋存形式,在区域人畜供水中发挥重要作用,裸露型岩溶区因其特殊水文地质结构,地下河易受到人类活动输入的影响。利用水文地球化学分析、水化学演化图(Hydrochemical Facies Evolution Diagram,HFE-D)、环境同位素辨析等多手段研究人类活动输入对开阳地下河水化学的影响。结果表明:阴阳主要离子分别是HCO_(3)^(-)、SO_(4)^(2-)和Ca^(2+)、Mg^(2+),水化学类型为HCO_(3)-Ca·Mg,主要受控于岩石风化控制,但地下河系统中SO_(4)^(2-)、NO_(3)^(-)及Cl^(-)受到南部县城、垃圾填埋场和渣场输入的影响。HFE-D发现地下河下游始终处于受影响状态,δ^(34) S-SO_(4)^(2-)同位素表明SO_(4)^(2-)主要来源生活污水输入(71%),其次是大气降雨(22%)。δ^(15) N-NO_(3)^(-)-δ^(18) O-NO_(3)^(-)同位素计算显示NO_(3)^(-)主要来源于污水排放(42%)、大气降雨(37%)和农业输入(21%),地下河系统的开放性不利于氮素的反硝化降解。

Subterranean rivers are an important form of karst water in southwestern China,playing a significant role in local water supply 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 environmental 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 HCO_(3)^(-) and SO_(4)^(2-),Ca^(2+)and Mg^(2+)respectively,with the hydrochemical type being HCO_(3)-Ca·Mg,mainly controlled by water-rock interaction.The SO_(4)^(2-),NO_(3)^(-) and Cl^(-)in the subterranean river system is impacted by the activity from the southern county,landfill and slag yard.The HFE-D indicated that the downstream section of the subterranean river was consistently affected by anthropogenic activities,and δ^(34) S-SO_(4)^(2-) isotopes suggest that sewage input accounts for the majority(71%)of the SO_(4)^(2-) source,followed by atmospheric precipitation(22%).Isotope calculations for δ^(15) NNO_(3)^(-) and δ^(18) O-NO_(3)^(-) indicate that NO_(3)^(-) is mainly sourced from sewage discharge(42%),atmospheric precipitation(37%),and agricultural inputs(21%).The openness of the bare karst subterranean river system hinders removal of nitrogen by denitrification.