Characteristics And Heterogeneous Reactions Of N₂O₅ And CINO₂ And The Influence Factors In Urban Jinan In Summertime

Heterogeneous reactions of reactive nitrogen oxides and the activation of chlorine are hot topics in atmospheric research fields.Dinitrogen pentoxide?N₂O₅?and its heterogeneous product nitryl chloride?CINO₂?play important roles in atmospheric chemistry,and subsequently contribute to regional brown haze and photochemical pollution.So far,the understanding of chemical behaviors of N₂O₅ and CINO₂ in the heavily polluted areas in mainland China remains unclear.In addition,chloride aerosols contribute a considerable fraction to fine atmospheric particulate matters.The mixing characteristics of chloride aerosols can alter the hygroscopic properties,which in turn affects heterogeneous reactivity.Therefore,in order to comprehensively understand the concentrations and heterogeneous transformations of N₂O₅ and CINO₂ in North China,we conducted field measurements at an urban site in summer and calculated the N₂O₅ uptake coefficients and CINO₂ product yields.In addition,we summaried and discussed the mixing characteristics and atmospheric implications of typical chloride aerosols.Chemical ionization mass spectrometry was deployed to dertermine the abundances of N₂O₅ and CINO₂ in real-time.Related trace gases,meteorological parameters,and inorganic water-soluble ions in PM2.5 were measured simultaneously.The observed N₂O₅ concentrations at surface level were relatively low,with an average nocturnal value of 22 pptv.The N₂O₅ concentration often peaked in the early evening,which was associated with thermal power plant plumes and residual ozone.Nocturnal N₂O₅ was lost very fast,mainly through heterogeneous reactions on aerosol surfaces.The estimated N₂O₅ uptake coefficients of six nighttime cases were in the range of 0.042?0.092,among the highest values obtained from ground based field measurements.The fast heterogeneous reactions of N₂O₅ on high loadings of aerosols generated relatively high levels of ClNO₂,with an average nocturnal concentration of 132 pptv.Despite the rich chloride content in fine aerosols,the ClNO₂ product yield was low,0.014 and 0.082 in two nighttime cases,much lower than the calculated values from the experiment-derived parameterization.According to the related researches in literatures,the suppressed chlorine activation in polluted urban atmospheres was attributed to the reduced hygroscopicity,solubility,and activity of chloride in real ambient aerosols due to internal mixing.This study obtained the levels,origins,and heterogeneous processes of N₂O₅ and CINO₂ in the summertime of urban Jinan and calculated the N₂O₅ uptake coefficient and CINO₂ product yield,explored the mixing characteristics of chloride aerosols and the subsequent influences of particulate hygroscopicity,reactivity and ClNO₂ product yield.The relavant results and conclusions make up the insufficiency of such a hot research topics in the polluted urban atmosphere in China,enrich the knowledge on heterogeneous chemistries of N₂O₅ and CINO₂,and provide scientific supports to regional atmospheric pollution control in future.