Source Apportionment Based On PMF Model And Pollution Characteristics Of Atmospheric VOCs

In recent years,the problem of atmospheric volatile organic compounds（VOCs）pollution has become increasingly serious.VOCs emissions in China’s atmospheric environment are huge and the sources of VOCs are complex.The accumulation of VOCs in the atmosphere is prone to secondary chemical reactions.In summer,VOCs is an important precursor of atmospheric environmental pollution events such as excessive ozone and photochemical smog.In China’s 14th Five Year Plan,VOCs replace SO₂,and become one of the five important indicators of atmospheric governance.In this study,Hefei was taken as an example.Through monitoring the atmospheric VOCs from June to August in 2018 to 2020,and a total of 56 components were detected.The composition and concentration of VOCs were analyzed,and the regional transport characteristics of atmospheric VOCs pollution in Hefei were identified based on the backward trajectory model and potential source contribution function（PSCF）method.Based on the positive matrix factorization（PMF）model,VOCs emission sources were analyzed.The ozone formation potential（OFP）and secondary organic aerosol（SOA）formation potential of VOCs were calculated based on the maximum incremental reactivity（MIR）method and fractional aerosol coefficients（FAC）method.The chemical reactivity of VOCs was comprehensively analyzed and the main active components were screened.Based on the method of VOCs health risk assessment,the health hazard assessment of atmospheric VOCs in Hefei was carried out.The main research results are as follows:（1）Study on regional transport characteristics of atmospheric VOCs pollution based on backward trajectory model and potential source contribution factor method.During the study period from 2018 to 2020,the volume fractions of total VOCs in Hefei were 26.32×10^-9,20.67×10^-9 and 30.35×10^-9 respectively.Through backward trajectory model and PSCF analysis,VOCs pollution in Hefei was mainly affected by air transport in northeast,east and southwest directions.The high potential contribution area of VOCs（WPSCF>0.5）is mainly concentrated in Hefei area and surrounding areas,and atmospheric VOCs pollution is mainly caused by the accumulation of local pollution sources.（2）Research on VOCs source resolution based on PMF model.Using PMF model to analyze VOCs sources,a total of 6 types of VOCs emission sources were detected.Liquefied petroleum gas（LPG）/natural gas（NG）sources and vehicle emission sources are the main contribution sources of atmospheric VOCs pollution,followed by industrial sources and solvent sources,natural sources and combustion sources are relatively low contribution sources.Combined with the tracer method of VOCs characteristic components,the main sources of VOCs pollution in Hefei are LPG/NG and vehicle emissions.（3）Study on the OFP and SOA generation potential of VOCs based on MIR method and FAC method.During the three observation periods from 2018 to 2020,the total OFP of VOCs in the atmosphere of Hefei was 198.0μg/m³,155.6μg/m³and 215.6μg/m³,respectively,and alkanes contributed the most to OFP.The total generation potential of SOA was 120.41μg/m³,86.86μg/m³and 98.57μg/m³,respectively.The contribution of aromatic hydrocarbons to the generation potential of SOA was the largest,accounting for more than 90%,and toluene was the VOCs component with the highest contribution to the generation potential of SOA.（4）Research based on health risk assessment of VOCs.In the non-carcinogenic risk assessment,the non-carcinogenic risk value of VOCs in Hefei City is within the safety threshold value.In the carcinogenic risk assessment,benzene and ethylbenzene have a small probability of risk,and the risk value of benzene and ethylbenzene shows an increasing trend year by year.