This study investigated the spatial distribution and genesis of iron(Fe),manganese(Mn),arsenic(As),nitrate nitrogen(NO_(3)-N),and ammonia nitrogen(NH_(3)-N)in groundwater across representative regions of Beijing Plain...This study investigated the spatial distribution and genesis of iron(Fe),manganese(Mn),arsenic(As),nitrate nitrogen(NO_(3)-N),and ammonia nitrogen(NH_(3)-N)in groundwater across representative regions of Beijing Plain(Yongding River alluvial fans-plains).An integrated methodology incorporating hydrochemical analysis,isotopic fingerprinting,sediment geochemistry,mineralogical and micromorphology analysis was systematically implemented.Analytical results demonstrated that groundwater As and NH_(3)-N concentrations remained below the Class Ⅲ water criteria of China's standard for groundwater quality.Groundwater NO_(3)-N,Fe,and Mn concentrations exceeded their Class Ⅲ standards in 7.69%,11.54%,and 19.23% of samples,respectively.Comprehensive assessments demonstrated that human health risks from groundwater hazard substances remained within acceptable thresholds.Mineralogical analysis results indicated that Fe/Mn-bearing minerals distributed in sediments were the primary geogenic sources of groundwater Fe/Mn.Furthermore,isotopic evidences coupled with hydrochemical fingerprints demonstrated that shallow groundwater NO_(3)-N concentrations were influenced by anthropogenic nitrogen inputs.Hydrogeochemical processes induced spatially heterogeneous distributions of As,Fe,Mn,NO_(3)-N,and NH_(3)-N concentrations in groundwater.In the northwestern piedmont area,groundwater Mn enrichment was mainly influenced by the underlying coal seams.The central alluvial fan area exhibited co-enrichment of NO_(3)-N and Fe primarily attributed to the combined effects of the geogenic Fe-bearing minerals dissolution under nitrifying conditions,manure and sewage inputs,and further intensified by the evaporation-concentration effects.In the southeastern alluvial plain,the co-enrichment of Fe and/or Mn concurrent with As/NH_(3)-N concentration fluctuation was governed by nitrate reduction,iron/manganese reduction,and iron/manganese-sulfate reduction processes.In addition,pH-dependent mineral dissolution-precipitation and adsorption-desorption further modulated the mobilization of As,Fe,and Mn in the alluvial plain area.These findings are crucial for groundwater protection and can also provide a scientific basis for ensuring drinking water security in Beijing.展开更多
基金supported by the Groundwater Environmental Background Value Investigation Research Project in the Beijing Plain area。
文摘This study investigated the spatial distribution and genesis of iron(Fe),manganese(Mn),arsenic(As),nitrate nitrogen(NO_(3)-N),and ammonia nitrogen(NH_(3)-N)in groundwater across representative regions of Beijing Plain(Yongding River alluvial fans-plains).An integrated methodology incorporating hydrochemical analysis,isotopic fingerprinting,sediment geochemistry,mineralogical and micromorphology analysis was systematically implemented.Analytical results demonstrated that groundwater As and NH_(3)-N concentrations remained below the Class Ⅲ water criteria of China's standard for groundwater quality.Groundwater NO_(3)-N,Fe,and Mn concentrations exceeded their Class Ⅲ standards in 7.69%,11.54%,and 19.23% of samples,respectively.Comprehensive assessments demonstrated that human health risks from groundwater hazard substances remained within acceptable thresholds.Mineralogical analysis results indicated that Fe/Mn-bearing minerals distributed in sediments were the primary geogenic sources of groundwater Fe/Mn.Furthermore,isotopic evidences coupled with hydrochemical fingerprints demonstrated that shallow groundwater NO_(3)-N concentrations were influenced by anthropogenic nitrogen inputs.Hydrogeochemical processes induced spatially heterogeneous distributions of As,Fe,Mn,NO_(3)-N,and NH_(3)-N concentrations in groundwater.In the northwestern piedmont area,groundwater Mn enrichment was mainly influenced by the underlying coal seams.The central alluvial fan area exhibited co-enrichment of NO_(3)-N and Fe primarily attributed to the combined effects of the geogenic Fe-bearing minerals dissolution under nitrifying conditions,manure and sewage inputs,and further intensified by the evaporation-concentration effects.In the southeastern alluvial plain,the co-enrichment of Fe and/or Mn concurrent with As/NH_(3)-N concentration fluctuation was governed by nitrate reduction,iron/manganese reduction,and iron/manganese-sulfate reduction processes.In addition,pH-dependent mineral dissolution-precipitation and adsorption-desorption further modulated the mobilization of As,Fe,and Mn in the alluvial plain area.These findings are crucial for groundwater protection and can also provide a scientific basis for ensuring drinking water security in Beijing.
