VOC emissions, evolutions and contributions to SOA formation at a receptor site in Eastern China

Volatile organic compounds (VOCs) were measured by two online instruments (GC-FID/MS and PTR-MS) at a receptor site on Changdao Island (37.99° N, 120.70° E) in eastern China. Reaction with OH radical dominated the chemical loss of most VOC species during the Changdao campaign. A photochemical age based parameterization method is used to calculate VOC emission ratios and to quantify the evolution of ambient VOCs. The calculated emission ratios of most hydrocarbons agree well with those obtained from emission inventory, but the emission ratios of oxygenated VOCs (OVOCs) are significantly lower than those from emission inventory. The photochemical age based parameterization method is also used to investigate primary emissions and secondary formation of organic aerosol. The primary emission ratio of OA to CO are determined to be 14.9 μg m 3 ppm 1 and SOA are produced at an enhancement ratio of 18.8 μg m 3 ppm 1 to CO after 50 h of photochemical processing in the atmosphere. SOA formation is significantly higher than the level determined from VOC oxidation under both high-NOx (2.0 μg m 3 ppm 1 CO) and low-NOx condition (6.5 μg m 3 ppm 1 CO). Polycyclic aromatic hydrocarbons (PAHs) and higher alkanes (>C10) account for as high as 17.4% of SOA formation, which suggests semi-volatile organic compounds (SVOCs) may be a large contributor to SOA formation during the Changdao campaign. SOA formation potential of primary VOC emissions determined from both field campaigns and emission inventory in China are lower than the measured SOA levels reported in Beijing and Pearl River Delta (PRD), indicating SOA formation cannot be explained by VOC oxidation in this regions. SOA budget in China is estimated to be 5.0–13.7 Tg yr 1, with a fraction of at least 2.7 Tg yr 1 from anthropogenic emissions, which are much higher than the previous estimates from regional models.