Research On The Characteristics Of The Surface Chemical Compositions And The Influential Factors Of Atmospheric Aerosol Particles In A Typical Urban Area Of Beijing

The environmental behavior of atmospheric aerosol particles depends largely on its surface chemical characteristics,so it is important to study the surface chemical characteristics of atmospheric aerosol particles.In this study,atmospheric aerosol particles were collected in a typical urban area of Beijing in 2014.The organic and inorganic components on the surfaces of the samples were analyzed using time–of–flight secondary ion mass spectrometry(TOF–SIMS).The variation characteristics of the surface chemical species and its particle size distribution,diurnal variation,pollution process change were studied.And the seasonal chemical composition of aerosol particles was compared.On the basis of this,the principal component analysis method was used to identify the likely pollution sources of the surface chemical components of atmospheric aerosol particles.The influence of air pollution process,meteorological factors and air mass transmission were discussed to study the influence of the chemical composition on the surface of atmospheric aerosol(1)Inorganic components such as crustal elements,heavy metals,sulfurous compounds,nitric compounds,ammonium compounds,siliceous compounds,fluorides,carbon–containing inorganics,and organic components such as alkyls,alkenyls,aromatic hydrocarbons,oxygen–containing organic groups,nitrogen–containing organic groups,silicon–containing organic groups,sulfur–containing organic groups and secondary groups were present on the surfaces of aerosol particles.The relative levels of secondary components such as oxygen–containing organic groups on the surfaces of aerosol particles increased during the haze event,indicating that aerosol particles aged during the sampling period.The interactions among the hydrophilic compounds,such as sulfurous and nitric compounds which formed in secondary reactions,and the hydrophobic compounds containing long–chain alkane groups,may alter the surface hydrophilicity/hydrophobicity of aerosol particles and affect their behavior in the environment.The toxic and harmful substances,such as fluorides,PAHs,and heavy metals can exert health hazards.(2)Four seasons of atmospheric aerosol particles in the study area were studied.The surface species varied with aerosol particle sizes.Crustal elements,fluorides,and siliceous compounds accumulated mainly on the surfaces of coarse particles(PM3.3–4.7);saturated and unsaturated straight–chain hydrocarbons and oxygen–containing organic groups accumulated mainly on the surfaces of fine particles(PM1.1–2.1);aromatic,medium–,and long–chain unsaturated hydrocarbons accumulated mainly on the surfaces of ultrafine particles(PM0.43–0.65).Some species displayed diurnal variation.Generally,the levels of organic components were higher in the daytime than at night,while the levels of inorganic components were higher at night than during the day.(3)The pollution sources of aerosol particles in different seasons and different air pollution processes were different in the study area.During the spring observation,the surface chemical composition of atmospheric aerosol particles is mainly from the source of motor vehicle exhaust,the construction construction dust,the long–distance transportation of industrial production activities and the secondary atmospheric chemical transformation process.During the summer observation,the source of atmospheric aerosol particles is mainly mixed source of fossil fuel combustion,incomplete combustion of biomass and fuel.During the autumn observation,the main source of atmospheric aerosol particles are incomplete combustion,biomass or plant burning,building dust,industrial emissions and secondary atmospheric chemical conversion.During the winter observation,the main source of atmospheric aerosol particles were motor vehicle exhaust emissions,winter coal–fired heating and secondary atmospheric chemical conversion.In order to reduce the pollution level of the surface chemical components of atmospheric aerosol particles in Beijing,the control of different pollution sources should be strengthened in different seasons,and the control of secondary pollution should be paid special attention.(4)In addition to influenced factors of the particle size,day and night,and sources of pollution,the pollution status,meteorological factors and air mass transfer also has some impact on the surface of the chemical composition of atmospheric aerosol particles.The more serious air pollution,the more complex the chemical composition of aerosol ions.The wind direction,wind speed and low velocity air mass from the south direction have a great influence on the surface chemical type and relative content of aerosol particles.The transport and transport of atmospheric air mass have a great influence on the surface chemical organic and inorganic chemical components of aerosol particles.During the study period,the pollution components on the surface mainly come from the pollutants carried by the weak or low velocity air mass in the south or northeast,and the adverse atmospheric diffusion conditions further aggravate the pollution caused by the local mobile source Accumulation and accumulation of things.