Ozone Source Apportionment During A Typical Photochemical Pollution Episode In Summer In The Yangtze River Delta

Since the beginning of21stcentury, national economy grows dramatically. With the rapiddevelopment of economy, urbanization and industrialization, the air quality in and around citiesbecome worse and worse. Ozone, as a significant ambient trace gas is beneficial for environmentand human health with a proper concentration. However, high concentration ozone in troposphereis the primary pollutant during photochemical pollution, which seriously threatens environment andpublic health. Especially for the highly nonlinear reactions among ozone, NOxand VOCs, whichcombined with chemical and physical processes such as horizontal and vertical transport anddiffusion, resulting the source and control factor researches in ozone become very complicated.Various pollution sources emit primary pollutants into atmosphere without planning and controlling,which deteriorates ecological environment and threatens human health. Therefore, controllingprimary pollutant emissions strictly, studying the formation and transport of air pollutants andenacting pollutant control policies have become serious environmental problems and academicissues in our country.Major cities in Yangtze River Delta were studied in this research. Based on the data fromphotochemical pollution in-line monitor in2013, July which is a typical heavy ozone pollutionmonth, is selected for this study. Additionally, based on the emission inventory of Yangtze Deltaregion in2013, WRF-CAMx modeling coupled with ozone source apportionment technique (OSAT)is adopted to simulate the heavy ozone pollution process in July. And ground-level O3sourceapportionment of5major cities (Hangzhou, Nanjing, Hefei, Shanghai Dianshan Lake and Shanghaiurban area) in Yangtze River Delta was studied in this research. Contributions from5source regionsand9major emission sectors to O3concentrations in these5major cities were also studied in thisresearch.According to the emission inventory result of Yangtze Delta in2013, the results among variouspollutant emissions were quite match. The emission quantities arranged from high to low were Jiangsu Province, Zhejiang Province, Anhui Province and Shanghai, among which Shanghai hadlowest emission absolute value. This is because Shanghai had lowest values in regional area,population and GDP compared with other three provinces. In2013, the total amount of SO2, NOx,PM2.5, VOCs and NH3in the three provinces and Shanghai city were2.7803,3.3514,2.0909,3.9418and1.6696million tons, respectively. In terms of spatial distribution, the pollution emissions werevery high and frequent from north to Nanjing and south to Hangzhou, Shaoxing, which could easilylead to regional air pollution under worse weather condition.From the result of ozone regional source apportionment through OSAT method, in terms ofspatial distribution, the influence from Zhejiang region to other sites become smaller and smallerfrom south area to north area, while the impacts from Jiangsu region become larger and larger. Fromwest to east, the regional contribution of other region (Anhui) become smaller and smaller. In termsof time sequences, the main source of O3during night was from super-regional transport and duringdaytime was from contributions within regions. However, different sites had different situations. Ingeneral, regional contributions had a close relationship with dominant wind direction. The resultsfrom two heavy ozone pollutions shows that regional contributions increased compared with wholeday or8-hour daytime during high ozone concentration period, which indicates that controlling localemission sources would have effective result in controlling high ozone concentration.From the O3source apportionment result in Yangtze Delta, there were no obvious differencesbetween daytime8-hour and maximum concentration sources of ozone during July. The majorsources in these sites were super-regional transport, process engineering, industrial boiler andfurnace source, mobile source and natural source. The contributions of O3pollutions during differentepisodes had different patterns. The results show that local sources were the main contributions todaytime ozone and local emissions had significant contributions to high ozone concentration.Therefore, controlling local emission sources is an effective way to reduce ozone concentration.