Pollution characteristics of organic carbon and elemental carbon in atmospheric particles during the summer day in Huangshi City

The atmospheric particle samples from the old and new towns of a typical mining city, Huangshi, were collected by miniVol (5 L · min^-1, 12 h, Airmetrics USA) during the summer day in July 2012. The carbonaceous components were quantified with the thermal/optical reflectance (TOR) method, which produced five organic carbon (OC) fractions, OC1, OC2, OC3, OC4, and pyrolyzed organic carbon (OP), and three elemental carbon (EC) fractions, EC1, EC2, and EC3. The results indicated that OC in PM₁₀ from the new and the old town were 14.60 μg · m^-3 and 18.70 μg · m^-3, respectively, and the EC were 4.70 μg · m^-3 and 11.02 μg · m^-3, respectively. OC in PM_2.5 from the new and the old town were 11.89 μg · m^-3 and 13.66 μg · m^-3, respectively, and the EC were 2.28 μg · m^-3 and 4.96 μg · m^-3, respectively. OC and EC in the old town were significantly higher, but sharing the same trend of variability with that in the new town. OC and EC in PM₁₀ mass fraction were higher than in PM_2.5. This suggested that carbon pollution in the old town was more serious, and carbon contents in big size particles of the summer day were higher. Based on the ratios of OC/EC and char-EC/soot-EC, we found that OC was largely secondary, while EC was usually soot-EC based. Coal combustion and motor vehicle tail gas are the important pollution sources in the summer day, with certain contribution from biomass combustion.