Nitrated Polycyclic Aromatic Hydrocarbon Pollution In Atmospheric Fine Particles During The Shanghai2010World Expo And Its Comparison Studies

There are huge number of vehicles in Shanghai which emit large quatities of engine exhaust and have negative impact on the air quality. Vehicle emissions has also become a major direct source of nitro-polycyclic aromatic hydrocarbons in fine particulate matter in the urban atmospheric. Shanghai municipal government had made significant efforts to improve air quality for the World Expo2010. A three-year plan was launched:some of construction sites were closed to decrease atmospheric PM10concentration; flue-gas desulfurization was installed in all coal fired power plants in order to remove sulfur dioxide (SO2) from exhaust flue gases and from the emissions of other sulfur oxide emitting processes; buses and taxies were upgraded and exhaust emission standards stage IV (equal to Euro4) was implemented from1October2009; open field biomass burning in surrounding area including neighboring Jiangsu and Zhejiang provinces were forbidden to reduce combustion emissions during Expo period. The objectives of this study were to (1) measure NPAH concentrations in Shanghai during the Expo;(2) characterize the influence of photochemistry on the formation of NPAH;(3) assess the influence of sources and source control measures on the PM2.5-bound NPAH concentrations.Atmospheric particulate matter with diameter<2.5μm (PM2.5) was collected at two sites (Xujiahui:residents commercial mixed sites; Baoshan:residents industrial mixed sites) in Shanghai. Gas chromatography/mass spectrometry with negative ion chemical ionization was used to measure the complex atmospheric aerosol samples after concentration of target fraction by HPLC. Nine nitrated polycyclic aromatic hydrocarbons (NPAHs) were quantitatively detected in the samples collected during World Expo, the average concentrations of NPAHs in PM2.5:Xujiahui:183pg· m-3Baoshan:260pg·m-3. Source analysis showed that the NPAHs of PM2.5are mainly derived from gas reaction in shanghai during World Expo. The result of comparing the concentrations of NPAHs in PM2.5showed that:After-expo> EXPO>Eve-expo,and the total average concentration of NPAHs during the After-expo was an order of magnitude higher than the other two period, even reached ng/m3.The results of comparing the2010and2008changes in the concentration of nitro-polycyclic aromatic hydrocarbons in airborne fine particles showed that:9NPAHs were detected in2010, however8NPAHs were detected in2008and6-NChr was not detected; And It has been proved by2-NF/1-NP source apportionment ratio method that the NPAHs of PM2.5are mainly derived from gas reaction in shanghai during2010and2008. The total average concentrations of the nine NPAHs over the investigated sites in2010were496pg·m-3,reduced by29%compared to the total annual average concentration of the samples collected in2008(695pg·m-3),and mostly reduction was happened at Xujiahui during spring,reduced by57%; The seasonal variation of concentrations of NPAHs during2010and2008shows:winter> spring (autumn)> summer. The pollution level of NPAHs of PM2.5during the World Expo reduced by25%compared with the same period in2008.There were some correlation between the concentrations of Na+、 NH4+、K+、F-、Cl-、NO3-and the total concentrations of NPAHs.