The Study Of The Relativity Between PM_2.5 And VOCs And The Mechanics Of Transformation From Typical VOCs To SOA In Shijiazhuang

Recently,the PM_2.5 pollution in Shijiazhuang has been severe,especially in winter.About 50% of these components are secondary organic aerosols?SOA?,which are converted from volatile organic compounds?VOCs?through a series of chemical and physical changes.The study of PM_2.5 variation and the relationship between VOCs and PM_2.5 are of great significance to the scientific haze prevention.From January 1,2015 to December 31,2015,the concentration of VOCs,PM_2.5 and other pollutants in the atmosphere of Yuhua District of Shijiazhuang City were continuously monitored.VOCs monitored mainly included non-methane hydrocarbons?NMHC?and oxygen Volatile organic compounds?OVOC?.Moreover,the content of water-soluble organic carbon?WSOC?in PM_2.5 has been detected.The influence of natural factors such as geography and meteorology on the ambient air quality and the pollution degree and seasonality of secondary organic carbon?SOC?in Shijiazhuang were analyzed.The influence of PM_2.5,NMHC and OVOC concentration on the air quality was also analyzed.And WSOC,WSOC,NMHC,OVOC sources,and the main pollutants in Shijiazhuang.The simulation of typical VOCs-acetone and ethyl acetate photo-oxidation process in Shijiazhuang with FASMILE software combined with MCM mechanism was discussed.Mechanism of Oxidation Transformation of VOC to SOA.The results show:The pollution of SOC in Shijiazhuang is serious,and the degree of pollution changes with the seasons: winter> spring> autumn> summer.that is,Winter and spring are more polluted by SOC than summer and autumn.In the winter,when the relative humidity is less than 56.7%,the mass concentration of PM_2.5 increased with the promotion of the relative humidity.When the relative humidity is 56.7 60%,the PM_2.5 concentration reached its maximum value,and does not change with the relative humidity.%,The PM_2.5 concentration decreased with the increase of relative humidity.When the relative humidity was between 56.7% and 60%,the formation of PM_2.5 was the most favorable.There was a significant positive correlation between the concentration of OVOC and the content of water-soluble organic carbon in fine particulate matter?f WSOC?.The correlation coefficients were R1 = 0.79,and R2 = 0.83.The correlation between NMHC and f WSOC was the highest,followed by OVOC.It can be deduced that OVOC and NMHC are the main sources of f WSOC.The OVOC and NMHC in air of Shijiazhuang in winter mainly come from the burning of fossil fuels?e.g.,coal,fuel oil?and biomass,followed by the emission of exhaust gas from diesel vehicles;Typical VOCs in Shijiazhuang-acetone,ethyl acetate and 1,3-butadiene,can be converted into acetaldehyde,formaldehyde,methanol and other secondary organic carbon through photooxidation reaction.And then through a series of complex physical and chemical reactions,ultimately forming the SOA.