Characteristics Of Organic Carbon And Elemental Carbon In Atmospheric Aerosols In The Urban Area In Beibei, A Suburb Of Chongqing

To investigate the pollutive characteristics of atmospheric carbonaceous aerosols in Beibei District, a suburb of Chongqing Municipal City, graded aerosol samples were continuously collected by cascade impactors over one year, from March 2014 to February 2015. Carbonaceous aerosols, including organic carbon (OC) and elemental carbon (EC), were detected by a DRI 2001A carbon analyzer. The results showed that the average annual concentrations of OC and EC in the PM2.1 were 16.3 +/- 7.6 and 1.8 +/- 0.7 mu g m(-3), and in the PM9.0 were 25.0 +/- 9.6 and 3.2 +/- 1.2 mu g m(-3), respectively. On the one hand, a more seasonal distribution of OC concentrations appeared in the PM2.1 (winter > spring > summer > autumn) than in the PM9.0 (winter approximate to spring approximate to summer > autumn); furthermore, whereas the OC significantly positively correlated with wind speed for both the PM2.1 (P < 0.05) and the PM9.0 (P < 0.01), it was negatively correlated with relative humidity (P < 0.05) for the latter. On the other hand, both the PM2.1 and the PM9.0 exhibited a more seasonal distribution of EC concentrations (winter > spring > summer > autumn), and the EC in the PM2.1 significantly negatively correlated with temperature (P < 0.05). Additionally, both the OC and the EC were concentrated mainly in the fine particles (< 2.10 mu m), and the size distributions of the OC in all four seasons displayed a bi-modal pattern that peaked in the size ranges of 0.43-0.65 mu m (for fine particles) and 4.7-5.8 mu m (for coarse particles), whereas the EC displayed a uni-modal pattern that peaked in the size range of 4.7-5.8 mu m (for coarse particles). Furthermore, the correlations between the OC and the EC were analyzed, and the SOC (secondary organic carbon) in the PM2.1 was estimated using the primary OC/EC ratio. It was found that the OC highly significantly correlated with the EC (P < 0.01), with the average annual concentration of the SOC being 6.3 +/- 5.9 mu g m(-3), which accounted for 33.5 +/- 22.6% of the OC. Analyzing the sources of the pollutive atmospheric aerosol in Beibei further demonstrated that it mainly originated in biomass burning, gasoline-vehicle exhaust, and coal combustion.