Study On Mechanism Of Submicron Aerosol Evolution In High Humidity Environment

Aerosol in the atmosphere is the most important factor causing haze.Especially submicron aerosol(PM1)has a more serious influence.For the one hand,PMi is rich in toxic and harmful substances and enters human alveolar blood,on the other hand,due to its small particle size,long residence time in the atmosphere and long transport distance,making its physical and chemical reactions in the atmosphere extremely complicated.Submicron aerosols are affected by many factors in the atmosphere.For example,relative humidity is one of the most important atmospheric aerosols.However,the effect of submicron aerosols on submicron aerosols in high temperature and high humidity is not clear.In particular,the effect of aqueous phase reaction and wet-removal effect needs to be further studied.In this paper,the mechanism of submicron aerosol evolution under high humidity was studied.From August 5,2016 to September 23,PM,was observed and analyzed in Binjiang District of Hangzhou City.The aerosol mass spectrometry(Including organic compounds,sulfates,nitrates,ammonium salts,chlorides)and particle size distribution of submicron aerosols were measured by HR-ToF-AMS.The correlation analysis was used to determine the presence of inorganic aerosols The origin of organic aerosol was analyzed by positive matrix model(PMF),and the effect of relative humidity on the source of organic aerosol was investigated.Submicron aerosols are affected by various factors,including the meteorological parameter such as temperature,humidity,wind speed,wind direction and radiation intensity,as well as the effects of SO2,NOx,VOCs and particulate matter emitted by sources.In this paper,through the correlation analysis with relative humidity,to make a comprehensive analysis of each factor and conclusions.The combined effects of aqueous phase oxidation and photochemical reactions at under high humidity were discussed.The changes of submicron aerosols were also analyzed according to the different emission levels of local emission sources.Relative humidity is focused on submicron aerosols evolution in this study,when relative humidity is high,SOA in organic aerosols and sulphate are mainly affected by the wet-removal effect,so their concentration become lower;when relative humidity is relative lower,the increase in humidity raises sulfate and SOA concentrations by promoting aqueous phase reactions.The aqueous phase reaction of nitrate with other components of organic aerosol is promoted either.The reason for this phenomenon is the limitation of deliquescence humidity of aerosol.Under the deliquescence humidity,the increase of the humidity promotes the aqueous reaction of the aerosol.When the relative humidity is higher than deliquescence humidity,the increase of humidity will promote the wet removal of aerosol.The increase of relative humidity promotes aerosol particle size growth.The effect of relative humidity on organic aerosols is obvious,which shows the effect of wet removal on secondary organic aerosols(SOA)and the accumulation effect on primary organic aerosols(POA).The emission of local sources will reduce the degree of aerosol oxidation.