AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Sources and Light Absorption Properties of Water-Soluble Organic Carbon in Beijing
ZHENYU DU, Kebin He, Fengkui Duan, Yuan Cheng, Jiumeng Liu, Rodney Weber, Tsinghua University
Abstract Number: 88 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract We investigated the sources and light absorption properties of PM2.5 water-soluble components in Beijing via samples collected from October 2011 to November 2012. Light absorption of PM2.5 water-soluble components at 365 nm (Abs365), used as a proxy for water-soluble brown carbon, correlated well with water-soluble organic carbon (WSOC) (monthly r2 always higher than 0.84), which suggested similar sources for WSOC and water-soluble brown carbon, though concentrations varied a lot among seasons. In winter, levoglucosan correlated well with both WSOC and Abs365, suggesting biomass burning was the main source for both WSOC and water-soluble brown carbon. In summer, the absorption of low biomass burning-impacted samples exhibited low correlation with levoglucosan and element carbon, indicating that sources related to secondary organic aerosols might be important. The mass absorption coefficients (MAE) of WSOC exhibited distinct seasonal variation with mean values of 1.27 m2/g in winter and 0.57m2/g in summer, which were approximately 2-3 times of the values in southeastern US. This difference might be caused by larger contribution of biomass burning or more anthropogenic-emitted precursors. PMF analyses attribute 39% and 51% of WSOC, and 54% and 20% of Abs365 to biomass burning and sources related to secondary organic aerosol formation, respectively. In addition, a factor with high percentage of EC contribute about 20% to Abs365, indicating the existence of primary sources other than biomass burning for brown carbon. We also analyzed some near-source samples to further investigate sources of water-soluble brown carbon, and the results were in-line with our PMF findings. Our results demonstrated the abundance of WSOC and water-soluble brown carbon in China, which may greatly influence climate and atmospheric photochemical processes.