Seasonal variation of carbonaceous pollutants in PM2.5 at an urban 'supersite' in Shanghai, China.

Multiple PM2.5 samples collected through different seasons from October 2011 to August 2012 at an urban site in Shanghai, China were analyzed for carbonaceous pollutants. Data from this site, a 'super' air quality monitoring station at Fudan University, has been used by researchers to investigate the formation mechanism of haze episodes. The characteristics and concentrations of organic carbon (OC), elemental carbon (EC), n-alkanes, as well as relative abundances of hopanes, in these samples were determined. The concentrations showed a pronounced annual cycle with higher values in cold seasons (spring and winter, mean: 8.6 μg/m(3), 3.3 μg/m(3) and 136.4 ng/m(3) for OC, EC and n-alkanes, respectively) and lower values in warm seasons (fall and summer, mean: 6.6 μg/m(3), 2.6 μg/m(3) and 73.8 ng/m(3) for OC, EC and n-alkanes, respectively). EC generally displayed a common source with that of OC in all seasons. Petroleum residue was the major source of n-alkanes, contributing 71.4% to the targeted C14-C33n-alkanes over four seasons. Principal components analysis and the composition of hopanes showed that emissions from vehicle exhaust contributed more carbonaceous aerosols than coal combustion. These data could provide important information for measures to reduce carbonaceous pollutant emissions and improve air quality in Shanghai, and other urban centers across China.