叶普曲高寒岩溶流域水化学特征及水质评价OA

As a vital component of the"Asian Water Tower",the water quality of alpine karst water is one of the most critical environmental challenges for sustainable development on the Qinghai-Xizang Plateau.The Lhasa river basin,a core water source area in Xizang,plays a pivotal role in both the health of local residents and the ecological security of Asia's water systems.However,current research on karst water predominantly focuses on low-altitude regions,leaving significant gaps in understanding high-altitude karst systems.This study focuses on the Yepuqu karst basin,a tributary of the Lhasa river in northern Xizang,to investigate the hydrochemical characteristics and water quality of both surface water and groundwater.The research aims to reveal the hydrochemical composition and water quality features of a typical alpine karst basin,as well as the key controlling factors influencing the water quality.The systematic collection of surface water and groundwater in the Yepuqu karst basin was analyzed using methods such as hydrochemical analysis,principal component analysis,single-factor index,and comprehensive pollution index.The results indicated that the milliequivalent percentages of Ca2+and HCO3-in the water bodies both exceeded 50％of their corresponding cations and anions,with the hydrochemical types of karst groundwater and surface water classified as HCO3-Ca and HCO3·SO4-Ca types,respectively.Ion balance diagram analysis showed that surface water was dominated by 83％calcite dissolution and 17％a combination of calcite and dolomite dissolution,while groundwater exhibited 67％calcite dissolution and 33％combined calcite-dolomite dissolution.The weathering and dissolution of rocks were the primary mechanisms controlling water mineralization,with both surface water and groundwater dominated by calcite dissolution,followed by combined dissolution of calcite and dolomite.Additionally,cation exchange reactions were also involved.The water quality analysis of the Yepuqu karst basin indicated that 86％of the 21 water samples evaluated by single-factor assessment belong to Class Ⅲ,while 14％were Class Ⅳ and Ⅴ.The comprehensive pollution index assessment further showed that the study area was of high-quality water.The results of two assessments showed certain discrepancies,primarily due to their differing assessment principles.Decision-makers can adopt a dual-track evaluation system combining"single-factor qualitative assessment+comprehensive pollution index quantitative assessment"to define different water quality conditions,thereby implementing more effective water resource management measures.This approach holds significant practical value for the comprehensive governance of water resources.Among them,Total Nitrogen(TN)was a key parameter in single-factor assessment,and the excessive nitrogen in water bodies primarily originates from fertilizer inputs.To address the issue of excessive TN levels in agricultural areas,an integrated prevention and control strategy of"source reduction,process interception,and smart monitoring"is recommended.This includes implementing crop rotation to reduce nitrogen fertilizer demand,applying soil testing-based formula fertilization with furrow-covering techniques to enhance nitrogen utilization efficiency,replacing chemical fertilizers with organic alternatives,and transforming drainage ditches into ecological filter beds to intercept nitrogen in runoff.Additionally,deploying soil moisture sensors for variable-rate fertilization can improve nitrogen agronomic efficiency.These measures collectively contribute to effective nitrogen management and water quality protection.The principal component analysis revealed that the primary factors influencing groundwater quality in the study area,ranked in order of significance,were anthropogenic activities,natural geological background values,and the composite effects of natural geological background and anthropogenic activities.For surface water quality,the key influencing factors followed the order of natural formation background values,anthropogenic activities,and the composite effects of natural geological background and anthropogenic activities.The results indicated that water quality in the study area was primarily influenced by three key factors:anthropogenic activities,natural formation background values,and the composite effects of natural geological background and anthropogenic activities.This study investigated the hydrochemical characteristics and water quality assessment of the Yepuqu alpine karst basin,which held significant theoretical and practical value for establishing a plateau water source protection system and safeguarding the ecological security of the"Asian Water Tower".