Forming Potential Of Secondary Organic Aerosols And Sources Apportionment Of VOCs In Summer And Autumn Of Shanghai, China

A continuous measurement was conducted in urban area of Shanghai from1st July to21st November,2011. The hourly mixing ratio of ambient VOCs in summer in the urban of Shanghai is (3.28-118.44)×10-9, and the average mixing ratio is (22.68±15.86)×10-9. The major compositions of VOCs were alkane, alkene, aromatic, and acetylene, accounting for48.77%,1.90%,13.03%and6.30%of the total VOCs, respectively. The hourly mixing ratio of ambient VOCs in autumn in the urban of Shanghai is (3.84-171.81)×10-9, and the average mixing ratio is (21.44±20.19)×10-9. The major compositions of VOCs were alkane, alkene, aromatic, and acetylene, accounting for53.58%,10.96%,27.98%and7.48%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 of Shanghai, in summer&autumn. During the most severe haze episode (10th-14th November) in autumn, it was dominated by the northwest wind, due to the combined action of the local high pressure, small wind and temperature inversion,it lead to a high air pollution process which last over48h, and the process include the transmission, accumulation, conversion, generation, development and dissipation.Fractional aerosol coefficients (FAC) was used to estimate the potential formation of secondary organic aerosols (SOA) in Shanghai, the SOA concentration in summer and autumn were2.05μg-m-3and1.44μg-m-3, respectively. The aromatics were not only the most important contributors to OFP, but also important SOA precursors.The result of by using the ratio of organic carbon and element carbon (OC/EC) was:(OC/EC)min was2.72, the average concentration of SOC and SOA in summer was3.27μg·m-3,and4.99μg·m-3; the average concentration of SOC and SOA in summer was3.24μg·m-3,and4.54μg·m-3;By applying the positive matrix factorization (PMF) model, six major sources were extracted to identify the sources of VOCs in autumn, Shanghai, including:vehicle exhaust (24.30%), incomplete combustion (17.39%), fuel evaporation (16.01%), LPG/NG leakage (15.21%), petrochemical industry (14.00%), 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 contribute37.39% of total VOCs concentration. Hence, these sources should be listed as priority of air pollution control strategy for Shanghai in future.