In-situ nitrogen fate in the vadose zone of different soil types and its implications for groundwater quality in the Huaihe River Basin,China

作者：Rongfu Li,Xiaohong Ruan,Tianhai Ma,Ying Bai,Congqiang Liu

摘要：This paper focused on nitrate fate in the vadose zone(VZ)and its implications for groundwater vulnerability under different soil types in the agricultural area of Huaihe River Basin,China.Isotopic compositions of nitrate(δ15N andδ18O)along with NO3-and Cl-concentrations were determined in the VZ-shallow groundwater continuum beneath silty-loam and silty-clay-loam,which are distinctive in texture and organic carbon(OC).In the soil zone(<1 m in depth),measuredδ18O-NO3-suggested the ubiquitous of nitrification regardless of soil types.In the subsoil zone(>1 m in depth),however,the concurrent enrichment ofδ15N-NO3-andδ18O-NO3-indicated the occurrence of denitrification,which showed a dependence on subsoil properties.Specifically,during wheat and maize land uses,denitrification removed as much as 76%-88%of the total nitrate where the subsoil was dominated by stratified OC-rich silty-clay-loam.In contrast,only 0%-28%of the nitrate was degraded via denitrification where the subsoil was composed of uniform,OC-depleted silty-loam.Furthermore,inactive denitrification and higher permeability in the silty-loam VZ implied higher groundwater vulnerability.This observation was consistent with the fact that groundwater NO3--N concentration beneath silty-loam(11.24 mg L-1)was over two times higher than that of the silty-clay-loam(5.32 mg L-1),where stricter fertilization management and conservation strategies should be applied to protect groundwater quality.

发文机构：MOE Key Laboratory of Surficial Geochemistry Department of Water Science Jinling Institute of Nanjing University Institute of Surface-Earth System Science

关键词：VadosezoneSilty-loamSilty-clay-loamNitrogentransformationGroundwatervulnerabilityStableisotopes

分类号： P64[天文地球—地质矿产勘探]