Characteristics Of Carbonaceous Components And Stable Isotope Tracing In Aerosols In Nanjing

Atmospheric aerosol samples were collected with different size in Nanjing Normal University and Nanjing College of Chemical Technology in January, April, July and October, representing winter, spring, summer and autumn respectively in2011. We discuss the pollution characteristics of particles, the acidity of fine particles and its correlations with oxalic acid and main water-soluble ions, the concentration characterics and size distribution of organic carbon and elemental carbon, the composition of stable carbon isotope of main sources and analyze the source of particles using isotope tracing method. The main conclusions are as follows:(1) The particulate matter pollution is serious since the concentrations of both fine particles and coarse particles have exceeded the limit in GB3095-2012; PM2.1and PM2.1～10show the same seasonal variation:winter> spring>autumn>summer.(2) It implies that the fine particles are acidic in Nanjing aerosols combining particle acidity and oxalic acid as well as related water-soluble ions while the increasing salts could reduce the acidity of aerosols and upgrade the acidification buffering capacity that could limit the formation of acid rain.(3) Pollution of OC and EC in industrial area is more serious than in urban area; Concentrations of OC and EC in winter and spring are obviously higher compared with those in summer, either for urban area or for suburban industrial area and the ratio of second organic carbon (SOC) in total organic carbon (TOC) is the highest in summer. Overall, OC and EC are enriched in fine particles below0.43μm. Logarithmic distribution and OC/EC ratio method imply that OC and EC mainly come from vehicles exhaust and coal combustion in fine particles while they are also related to biomass combustion and cooking in coarse particles.(4) Correlation analysis and isotopic signatures of potential sources suggest that carbonaceous contents mainly come from gasoline vehicles exhaust in urban area, and that may be attributed to the vehicle exhaust emissions and industrial emissions in suburban area. In addition, coal combustion, biomass burning and geological sources may have important contribution to aerosols in winter and spring. Back trajectory analysis implies that the long-range transport has considerable contribution to the carbonaceous aerosol in winter and spring. However, the major sources may be attributed to local emissions in the other two seasons.