Atmospheric nitrate-nitrogen dry deposition characteristics and source analysis in the Xichuan reservoir area of Danjiangkou Reservoir
The research focused on the Xichuan Reservoir area of the Danjiangkou Reservoir,where five monitoring points were established for collecting dry deposition samples from January to December 2021.Analyses were conducted on the samples,including assessments of nitrate concentration,flux,and nitrogen and oxygen isotopes.The Stable Isotope Analysis in R(SIAR)model was employed to quantify the primary sources of nitrate.The results indicated that the monthly average nitrate concentration in dry deposition within the reservoir area was 0.16mg/L.The annual flux of nitrate dry depositions was determined to be 2.49kg/(hm2·a),with monthly mean values of δ15N-NO3-and δ18O-NO3-being(+ 0.17±4.10)‰ and(+56.6±9.18)‰,respectively.Significant seasonal variations were observed in nitrate concentration,deposition flux,and nitrogen and oxygen isotopes.During the autumn and winter seasons,both nitrate concentration and deposition flux were higher than those in the spring and summer,primarily attributed to the increased emissions from fossil sources during cold seasons,enhanced atmospheric boundary layer stability,and a shift towards particle-phase nitrate formation in aerosol-gas conversion equilibrium.The highest δ15N-NO3-in winter was associated with increased nitrogen isotope fractionation due to winter coal-fired heating and low temperature,while the lowest δ18O-NO3-in summer was linked to the dominance of the NO2 +·OH pathway in nitrate formation.The results of SIAR analysis revealed that the main sources of nitrate in dry deposition within the reservoir area were fossil sources(traffic emissions and coal combustion),with a contribution rate of 69.3%,of which the contribution rates of traffic emissions and coal combustion sources were 51.1%and 18.2%,respectively.The contribution of fossil sources was highest in winter(72.0%),with 70.4%originating from traffic emissions.This further confirmed that traffic emissions and winter coal combustion were the primary factors influencing nitrate in dry deposition within the reservoir area.Controlling pollution from traffic sources and coal combustion is crucial for reducing atmospheric nitrate levels in the future.In addition,the relatively stable contribution of biomass-burning sources emphasized the importance of external inputs in nitrate dry depositions within the reservoir area.
dry depositionnitratenitrogen and oxygen isotopestable isotope model(SIAR)backward trajectory
万方数据
维普
