| The hazard of PM2.5 is closely related to the type and content of the chemical components contained in it.In this study,the quality reconstruction of PM2.5 in the four seasons of spring,summer,autumn and winter in Chengdu from 2013 to 2014 was reconstructed and reconstructed by chemical mass reconstruction method.In the process,the localized quality reconstruction conversion coefficient is derived according to the environmental conditions of Chengdu and the pollutant discharge list.The seasonal variation characteristics of PM2.5components were analyzed based on the reconstruction results.Further,the on-line single-particle aerosol mass spectrometer SPAMS was used to study the chemical component content of PM2.5 in Chengdu during the winter of 2015-2017,and combined with the reconstruction results in winter 2014,the PM2.5 content of Chengdu in the winter of 2014-2017 was analyzed.Yearly trends.Research indicates:The main components of PM2.5 can be classified into five kinds of crustal materials,trace elements,EC,OM and water-soluble inorganic ions.The calculation method for the concentration of crustal material is GM=2.14[Si]+1.89[Al]+1.67[Mg]+1.43[Fe]+1.67[Ti]+1.58[Mn]+0.381[Al];the measured concentration of trace elements and elemental carbon is its component concentration;OM is divided into POA and SOA,and the concentration is determined by POC and SOC respectively.Multiplied by the conversion coefficients k1,k2;the inorganic salts composed of water-soluble inorganic ions are present in the form of ions in PM2.5,and can be divided into primary ions and secondary ions,respectively,the concentration is the sum of the ion concentrations contained in the two Adsorbed water was calculated by PBW=0.24(SO42-+NH4+).The conversion coefficient k1 is the OM/OC mass ratio of the POA,calculated according to the Chengdu PM2.5 emission inventory and the source component spectrum,k1=1.35;the conversion coefficient k2 is the OM/OC mass ratio of the SOA,according to the Chengdu VOCs emission list and“The two-product model method”calculates k2=1.79.The reconstruction expression of PM2.5 is PM2.5=?GM+Trace+EC+POA+PIN?+?SOA+SIN?+PBW,and the reconstituted concentrations in spring,summer,autumn and winter are60.259 ug/m3 and 42.476 ug/m3,70.559 ug/m3,116.096 ug/m3,accounting for 87.19%,83.40%,97.01%,92.75%of the measured concentrations of PM2.5,respectively,and the proportion in summer is small,mainly with high OM/OC quality of summer organic aerosols.More relevant.The seasonal variation characteristics of PM2.5 components are as follows:the mass concentration of each component is the same as that of the fall,and the other components have the same change pattern:winter>autumn>spring>summer.The change of content is more complicated,the content of crustal material is the highest in spring;the content of trace elements in the four seasons is about 1%,and the seasonal variation is not obvious;the content of EC and POA is higher in autumn and winter;the content of primary inorganic ion is the highest in winter,spring and autumn It is the lowest in summer;SOA is higher in summer and autumn,followed by winter and spring is the smallest;SO42-content in secondary inorganic ions is higher in summer and autumn,lower in spring and winter,highest in winter in NO3-,lower in spring and autumn,lowest in summer,and lower in NH4+There is no obvious seasonal variation;the adsorption water is consistent with the change of secondary inorganic ions.If only one component and two components are analyzed,the secondary component content in each of the four seasons is greater than the primary component,indicating the importance of the precursor to PM2.5 contribution.Using SPAMS to study the chemical composition of PM2.5 in winter 2015-2017,combined with the results of PM2.5 reconstruction in winter 2014,the annual variation trend of PM2.5 components in 2014-2017 was analyzed.The results were:crustal materials and trace elements.The content of NH4+salt fluctuated and there was no rising or falling trend.The content of EC and NO3-salt increased as a whole,and the content of OM and SO42-salt decreased overall. |
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