Sources Of Nitrate Nitrogen Deposition And Prevention And Control Measures In The Xichuan Reservoir Area Of Danjiangkou Reservoir

Taking the Xichuan reservoir area of Danjiangkou reservoir as the research object,dry and wet deposition samples were collected from January 2021 to December 2021 from five atmospheric monitoring points set up around the reservoir area,particulate matter,HNO₃ gas and wet deposition samples in the reservoir area were collected,nitrate and nitrogen concentrations and nitrogen and oxygen stable isotopes in the samples were measured,nitrate concentrations and isotopic characteristics in dry and wet deposition in the reservoir area were analyzed,and the atmospheric The main sources of nitrate pollution in the atmospheric deposition were analyzed.The results showed that.（1）The monthly average concentrations of NO₃^-in particulate matter and atmospheric HNO₃ in the reservoir area were 1.16μg·m^-3 and 37.02μg·m^-3,respectively,and the monthly average concentration of NO₃^-in wet deposition was 0.27 mg·L^-1.The monthly average concentrations of NO₃^-in particulate matter and atmospheric HNO₃ in the reservoir area showed highly significant differences in time（P<0.01）,and the monthly average concentrations of NO₃^-in particulate matter,HNO₃ gas and wet deposition were 0.27 mg·L^-1.The monthly mean concentrations of NO₃^-in deposition all showed higher in winter than in summer.（2）Theδ¹⁵N-NO₃^-andδ¹⁸O-NO₃^-values of NO₃^-in particulate matter and atmospheric HNO₃ in the reservoir area were 2.09‰and 77.6‰,4.99‰and 30.2‰,respectively;theδ¹⁵N-NO₃^-andδ¹⁸O-NO₃^-values in wet deposition were-5.44‰and59.29‰,respectively.The values ofδ¹⁵N-NO₃^-andδ¹⁸O-NO₃^-in both particulate matter and HNO₃ gas were highly significantly different in time（P<0.01）.Theδ¹⁵N-NO₃^-andδ¹⁸O-NO₃^-values in particulate matter,HNO₃ gas and wet deposition in the reservoir area were higher in winter than in summer.（3）The mean values of the contributions of the two formation pathways of OH(f_p1)and N₂O₅(f_p2)for atmospheric nitrate during the sampling period were 62±24%and 38±24%,respectively,and the contributions of the two pathways of OH(f_p1)and N₂O₅(f_p2)for the four seasons of spring,summer,autumn and winter were 66±1%and 34±1%,90±2%and10±2%,68±7%and 32±7%,24±5%and 76±7%,respectively.7%,24±5%and 76±5%.（4）Nitrate in HNO₃ gas and particulate matter and wet deposition in the reservoir area are mainly from fossil sources such as traffic emissions and coal combustion,with contributions of 64%,52%and 51%.The contributions of fossil sources in HNO₃ gas,particulate matter and wet deposition show seasonal variation characteristics,with HNO₃ gas being the highest in winter,particulate matter in summer and wet deposition in spring.（5）Based on the source of nitrate in atmospheric deposition in the reservoir area,the nitrogen pollution prevention and control measures of"source control"are proposed,mainly from the control of coal combustion and traffic emissions to reduce NO_x emissions in 2aspects.