Modelling air quality during the EXPLORE-YRD campaign - Part Ⅱ. Regional source apportionment of ozone and PM_(2.5)

摘要

A source-oriented Community Multiscale Air Quality model was used to quantify the contributions of different sources to ground-level fine particulate matter (PM2.5) and ozone (O-3) over the Yangtze River Delta (YRD) region during the EXPLORE-YRD (EXPeriment on the eLucidation of the atmospheric Oxidation capacity and aerosol foRmation, and their Effects in the Yangtze River Delta) campaign (17 May to June 17, 2018). O-3 formation in most urban areas of YRD is attributed to volatile organic compounds (VOCs) (81.1%, 78.5%, 60.2%, and 55.1% in Shanghai, Nanjing, Hefei, and Hangzhou, respectively), but is affected more by nitrogen oxides (NOx) in suburban and rural areas. Industry and transportation are the two major sources of O-3 and PM2.5. In addition to the two sources, NOx produced owing to power generation, and VOC emissions from biogenic sources are important source of O-3. Industry contributes the most to the total mass of PM2.5 in the YRD during the study period (9-25 mu g/m(3)), followed by transportation (2-7 mu g/m(3)). Industry, residential emissions, and transportation are the major sources of primary organic carbon and elemental carbon, whereas industry, transportation, and power generation account for most of the sulphate (SO2-4) and nitrate (NO-3) in the YRD. Agriculture is the most dominant source of ammonium emissions (NH+ 4). In Shanghai, Nanjing, Hefei, and Taizhou, secondary organic aerosol (SOA) are mainly contributed by industrial emissions. However, in Hangzhou, biogenic emissions contribute more than 40% of SOA. During all types of pollution episodes, industry and transportation are generally the two greatest sources of O-3 and PM2.5 in YRD. The contribution of industry is higher during high PM2.5 pollution episodes, whereas biogenic and open burning contributions are more important during high O-3 episodes. Overall, anthropogenic sources dominate the formation of O-3 and PM2.5 pollution in the YRD, whereas biogenic emissions contribute significantly to O-3 attributable to VOC emissions (O3_VOCs) accounting for 9-20% in urban areas of the YRD.