Characterization of carbon fractions in carbonaceous aerosols from typical fossil fuel combustion sources

Understanding of carbonaceous aerosols from different combustion sources and their optical properties are important to better understand atmospheric aerosol sources and estimate their radiative forcing. In this study, eight organic carbon (OC) and elemental carbon (EC) sub-fractions and light absorption properties of EC are investigated using thermal/optical method and compared among six typical solid and liquid fossil fuel combustion sources (e.g., coal combustion, industry, power plant, diesel and gasoline vehicle, and ship emissions) and within each source type, with consideration of different fuel types and combustion conditions. The results indicate that OC and EC sub-fraction distributions and mass absorption efficiency of EC (MAE_EC) are sensitive and specific to sources, fuels, combustion and operating conditions. The differences in carbon fractions and MAE_EC between solid and fossil fuel source emissions are statistically significant (p < 0.05). The average MAE_EC from liquid fossil fuel sources (7.9 ± 3.5 m²/g) are around1.5-fold higher than those from solid fossil fuels (5.3 ± 4.0 m²/g). Correlation analysis indicates that light attenuation of EC positively correlates with EC1 and EC2 fractions with correlation coefficients (r) around 0.6, while negatively correlates with the percentages of OC2 and OC3 in total carbon. Inter-comparisons of distributions of carbon sub-fractions and MAE_EC from different coal samples indicate the tested new stoves and honeycomb-like shape may contribute to lower EC emission factors but with stronger light absorptivity of EC, suggesting curbing short-lived pollutants (e.g., EC) with improvement of coal stoves and “clean” coal at current stage might not always result in co-benefits of air quality and climate.