Abstract Number: 12 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Biomass burning, the largest global source of elemental carbon (EC) and primary organic carbon (OC), is strongly associated with many subjects of great scientific concern such as secondary organic aerosol and brown carbon. The characteristics of biomass burning aerosol were investigated based on both ambient samples collected in Beijing and sources emission samples derived from stove combustion. The high levoglucosan concentrations and the low winter to summer ratios of levoglucosan indicated significant impact of biomass burning activities throughout the year in Beijing. Comparison of levoglucosan and water soluble potassium (K+) levels suggested that it was acceptable to use K+ as a biomass burning tracer during summer in Beijing, while the contribution of fireworks to K+ could be significant during winter (e.g., the Spring Festival period). Moreover, the levoglucosan to K+ ratio was found to be lower during the typical summer period (averaging 0.21) compared with the typical winter period (averaging 0.51). On the other hand, levoglucosan correlated strongly with mannosan throughout the winter and the levoglucosan to mannosan ratio averaged 9.49, whereas levoglucosan and mannosan exhibited relatively weak correlation during the typical summer period and the levoglucosan to mannosan ratio averaged 12.65. Results from PMF modeling showed that about 50% of the OC and EC in Beijing were associated with biomass burning processes. In addition, a new source-identification method was developed based on the comparison of the levoglucosan to K+ ratio and the levoglucosan to mannosan ratio among different types of biomass. Using this method, the major source of biomass burning aerosol in Beijing was suggested to be the combustion of crop residuals, while the contribution from softwood burning was also non-negligible, especially in winter.