| In order to study the composition characteristics of polycyclic aromatic hydrocarbons(PAHs)produced by different emission sources and their photolysis reactions,a set of pipeline dilution system was used to collect particulate matter samples generated from wood combustion,civil coal combustion,automobile exhaust gas,and gasoline samples.Pieces,the collected samples were exposed to natural sunlight for different periods of time.At the same time,30 surface soils(0-3 cm)of typical emission characteristics locations in Wuhu City were collected,for a total of 126 samples.Gas chromatography-mass spectrometry(GC-MS)was used to determine the concentration of 16 PAHs in the sample,and analyze the composition characteristics of PAHs produced by different emission sources and the changes in composition characteristics before and after photolysis.Exponential fitting is performed on the photolysis data,and the curve equation of the concentration change with time and the photolysis rate constant are obtained.Analyze the composition spectrum of PAHs from typical sampling sites,use characteristic ratio method and positive definite matrix factor method(PMF)to analyze the source of typical samples,use previous research results and the component characteristics obtained in this study to determine the source of PMF factors,respectively Substitute the original concentration,the corrected concentration of the photolysis rate constant in the literature,and the corrected concentration of the photolysis rate constant in this study,and compare the contribution rates of each source under different methods.The following main understandings are found through research:(1)Polycyclic aromatic hydrocarbons produced by different emission sources have different composition characteristics.The PAHs produced by firewood combustion are mainly in the middle and high rings,with the middle ring accounting for 43% and the high ring accounting for 49%,among them,Fla and Pyr account for a relatively high proportion;The polycyclic aromatic hydrocarbons produced by coal combustion emissions are also dominated by medium and high rings,with the middle ring accounting for 36% and the high ring accounting for 60%,among them,Bb F and Ba P account for a relatively high proportion;The polycyclic aromatic hydrocarbons emitted by volatile oil are mainly low-ring,accounting for 94%,among them,NaP has the highest proportion,exceeding 80%;The polycyclic aromatic hydrocarbons emitted from automobile exhaust are mainly high-ring,accounting for 67%,and middle-ring accounting for 29%,among them,Chry,Ba P,Dah A,and Bk F account for a relatively high proportion.(2)In terms of total concentration,based on the photolysis data index fitting equation,the residual concentration of PAHs produced by different emission sources accounted for different proportions of the original concentration after photolysis.Coal combustion emissions have the highest degree of photolysis,followed by wood combustion and oil volatile,traffic exhaust emissions.In terms of composition characteristics,the composition characteristics of PAHs produced by different emission sources after photolysis have changed.The main manifestations are that the proportion of middle rings decreases,the proportion of high rings becomes higher,and the oil volatile emissions remain low after photolysis.The highest proportion.In terms of the degradation rate of monomeric PAHs,among the monomeric PAHs emitted from wood combustion,Acy,Phe,and Na P have faster photolysis rates,and the photolysis rate constants are 5.2317,3.4932,and 2.9596;Among the PAHs emitted from coal combustion,the photolysis rate constant of Fla is 3.1428;Among the monomeric PAHs emitted by volatile oil,Pyr has the fastest photolysis rate,with a photolysis rate constant of 2.1612;Among the monomeric PAHs emitted from traffic exhaust,Bb F and Fluo have faster photolysis rates,and the photolysis rate constants are1.2032 and 1.0324.(3)There are certain differences in the PAHs concentration and composition characteristics of typical sampling sites.The average concentration of ∑16PAHs in the traffic area samples is in the range of 904.63-4804.20ng/g,and high-ring polycyclic aromatic hydrocarbons account for a relatively high proportion;The average concentration of ∑16PAHs in the sample points affected by oil volatilization is in the range of162.19ng/g—4768.7 ng/g,and mid-ring and high-ring polycyclic aromatic hydrocarbons account for a relatively high proportion;The average concentration of ∑16PAHs in the sample points affected by coal combustion is between 1697.52-26063.05 ng/g,and the middle-ring and high-ring polycyclic aromatic hydrocarbons account for a relatively high proportion;The average content of ∑16PAHs in the sample points affected by the burning of wood was 269.68 ng/g,and the middle-ring polycyclic aromatic hydrocarbons accounted for a relatively high proportion.(4)Using the concentration corrected by the degradation rate constant obtained in this study to perform the characteristic ratio,the ratios of emission sources of the same category are automatically gathered,and the original threshold interval no longer meets the judgment result.Therefore,this study proposes the threshold interval of the characteristic ratio method.Proposed changes.(5)There are differences in the source contribution rate obtained by PMF source analysis using the original concentration,the concentration after the correction of the photolysis rate constant of the literature,and the concentration after the correction of the photolysis rate constant in this study.The contribution rate of the traffic source of the traffic emission area is significantly reduced after the photolysis rate constant is corrected in this study;The contribution rate of coal combustion sources in coal combustion areas has increased significantly after correction of the photolysis rate constant in the literature;The contribution rate of firewood burning in the firewood burning area has been significantly increased after the photolysis rate constant of this study is corrected. |
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