[Forming potential of secondary organic aerosols and sources apportionment of VOCs in autumn of Shanghai, China].

A continuous measurement was conducted in urban area of Shanghai from 1stSeptember to 21st November, 2011. The mass concentration of PM2.5 and the mixing ratio of VOCs were obtained during the period. Four pollution episodes were observed: PD1 (20th-23th September), PD2 (5th-9th October), PD3 (13rd - 18th October), PD4 (10th - 14th November). The average mass concentrations of PM2.5 were (45+/-16), (76+/-46), (57+/-36) and (122+/-92) microg.m-3, respectively. The mixing ratio of VOCs were (30.87+/-30.77) x10(-9), (32.09+/-30.69) x10(-)9, (34.04+/-28.13) x10(-9) and (44.27+/-31.58) x10(-9). Alkane, alkene and aromatic hydrocarbons accounted for 53. 58% , 27. 89% , and 10. 96% of the total VOCs, respectively. The OH radical loss rate (LOH) and the ozone formation potential (OFP) were applied to assess the chemical reactivity of VOCs, the results showed that the alkenes and aromatics were the most important contributors to LOH and OFP in the atmosphere in the urban area of Shanghai, in autumn. Fractional aerosol coefficients (FAC) and the ratio of organic carbon to element carbon (OC/EC) were used to estimate the potential formation of secondary organic aerosols (SOA) in Shanghai, the SOA concentration values obtained by the two methods were 1.43 microg.m-3 and 4.54 microg.m-3, respectively. The value predicted by OC/EC was significantly higher, which was mainly due to the low amount of SOA precursors measured in this study. The aromatics were not only the most important contributors to OFP, but also important SOA precursors. By applying the positive matrix factorization (PMF) model, six major sources were extracted to identify the sources of VOCs in autumn in Shanghai, including vehicle exhaust (24.30%), incomplete combustion (17.39%), fuel evaporation (16.01%) , LPG/NG leakage (15.21%) , petrochemical industry (14.00% ), and paint/solvent usage (13.09%). Vehicle exhaust and paint/solvent usage contain abundant aromatics species which are the most important contributors to OFP and important SOA precursors. The above two sources contributed 37.39% of the total VOCs concentration. Hence, these sources should be listed as priority of air pollution control strategy for Shanghai in future.