Nitrated polycyclic aromatic hydrocarbon pollution during the Shanghai World Expo 2010

Atmospheric particulate matter with aerodynamic diameter <2.5 μm (PM2.5) was collected at Xujiahui and Baoshan in Shanghai, China in 2010 when the World Expo took place. Eight nitrated polycyclic aromatic hydrocarbons (NPAHs) were analyzed. Significant reductions in individual NPAH (69-324%) and the mean ΣNPAH (about 140%) concentrations were measured during the Expo period. In order to minimize the influence from the meteorological condition, individual NPAH concentrations of 2010 Expo period were compared with those in the same time period from 2008. Significant effects from the source control measures were revealed, i.e., the individual NPAH concentration reductions ranged between 31% and 477% at the mixed residential and industrial Baoshan site, and only 0-88% at the urban Xujiahui site. The relatively high 2-nitrofluoranthene/1-nitropyrene ratio values (11-31) suggested a predominance of photochemical formation of NPAHs in the atmosphere during the Expo period. It could be concluded that the air quality during the Shanghai World Expo 2010 was benefited from the following three factors; (1) source control measures during the Expo period, i.e., prohibition of open field biomass burning in surrounding areas, (2) the three-year plan implemented from October 1, 2009, including construction sites shut-down, flue-gas desulfurization/denitrification and the vehicle upgradation and (3) the Asian monsoon which brings in clean air from the ocean during spring and summer into Shanghai.