首页|Hydrogeochemical and isotopic assessment of the origin of NO3-and N-NH3 contents in the aquifer located in a closed lacustrine volcano-sedimentary basin in the metropolitan area of Mexico City
Hydrogeochemical and isotopic assessment of the origin of NO3-and N-NH3 contents in the aquifer located in a closed lacustrine volcano-sedimentary basin in the metropolitan area of Mexico City
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Hydrogeochemical and isotopic assessment of the origin of NO3-and N-NH3 contents in the aquifer located in a closed lacustrine volcano-sedimentary basin in the metropolitan area of Mexico City
To explain the presence and spatial distribution of NO3-and N-NH3 in the Aquifer of the Metropolitan Area of Mexico City(AMAMC),a hydrogeochemical and iso-topic analysis using 13CDIC(as well as the stable isotopes 18O and 2H)in groundwater was conducted.This aquifer is located in an old closed lacustrine volcano-sedimentary basin;some wells hosted in the semi-confined zone contain high N-NH3 concentrations,while others present NO3-contents in the recharge zones(hosted in an oxidizing envi-ronment).In this study,a change in the isotopic signature(primarily in 18O and 2H)was observed from the recharge zones to the basin center in some of the wells with high NO3-concentrations,this behavior can be attributed to evaporation during the incorporation of recently infiltrated water.In addition,the results for 13C(along with 2H)in wells with the highest N-NH3 concentrations exhibited an atypi-cally broad range of values.Results indicated the occurrence of hydrogeochemical and/or biochemical processes in the aquifer(in an oxidizing or reducing environment),such as organic degradation,bacterial decomposition(primarily in the ancient Lake Texcoco and which acts as a natural sink for carbon,nitrogen,sulfur,and phosphorus),besides rock weathering and dissolution,which may be responsible for a very marked isotopic modification of the 13C(and,to a lesser extent,2H).Methanotrophic bacterial activity and methano-genic activity may be related to N-NH3 removal processes by oxidation and residual water incorporation respectively,whereas the increase in the NO3-content in some wells is due to the recent contribution of poor-quality water due to contamination.
18O and 13C isotopesIronHydrogeochemical processesNitrateNitrogen species
José Iván Morales-Arredondo、María Aurora Armienta Hernández、Joel Edmundo Ortega-Gutiérrez、Elisa Cuellar Ramirez
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Natural Resources Department,Institute of Geophysics,National Autonomous University of Mexico,Ciudad Universitaria No.3000.Col.Copilco Universidad,Coyoacán Delegation,04360 Mexico,CDMX,Mexico
Instituto Politecnico Nacional,Calz.Ticomán 55,La Laguna Ticoman,07340 Mexico,CDMX,Mexico
Benemérita Universidad Autónoma de Puebla Ciudad Universitaria,Col.San Manuel,Puebla,Pue,Mexico
18O and 13C isotopes Iron Hydrogeochemical processes Nitrate Nitrogen species
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