VOC Characteristics and Their Source Apportionment in the Yangtze River Delta Region during the G20 Summit

To evaluate the effectiveness of measures to reduce the levels of volatile organic compounds (VOCs), which are important precursors of ground-level ozone formation, the real-time monitoring data of VOCs at the urban Zhaohui supersite (ZH), the Dianshan Lake regional supersite (DSL) and the urban Yixing station (YX) in the Yangtze River Delta region were analyzed from 23 August to 15 September 2016 during the G20 Hangzhou Summit. The average mole ratios of VOCs at the three sites were 6.56, 21.33 and 19.62 ppb, respectively, which were lower than those (13.65, 27.72 and 21.38 ppb) after deregulation. The characteristics of the VOCs varied during the different control periods. Synoptic conditions and airmass transport played an important role in the transport and accumulation of VOCs and other pollutants, which affected the control effects. Using the positive matrix factorization (PMF) method in source apportionment, five factors were identified, namely, vehicle exhaust (19.66-31.47%), plants (5.59-17.07%), industrial emissions (13.14-33.82%), fuel vaporization (12.83-26.34%) and solvent usage (17.84-28.95%) for the ZH and YX sites. Factor 4 was identified as fuel vaporization + incomplete combustion (21.69-25.35%) at the DSL site. The Non-parametric Wind Regression (NWR) method showed that regional transport was the main factor influencing the VOC distribution.