AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Source Apportionment of Pb-containing Particles by Multiple Methods during January 2013 in Beijing, China
JING CAI, Jiandong Wang, Yanjun Zhang, Hezhong Tian, Shuxiao Wang, Deborah Gross, Mei Zheng, Peking University
Abstract Number: 682 Working Group: Source Apportionment
Abstract Though leaded gasoline has been banned in Chinese megacities since 1997 and nationally since 2000, lead (Pb) is still an important issue in China as its concentration in megacities like Beijing remains high. Traditionally, Pb source apportionment studies have been conducted with receptor models or emission inventories (EI), which results in low-time resolution and large variability of results. In this study, both receptor-oriented and source-oriented methods were used to identify the major sources of Pb in Beijing in January 2013.
Samples were collected using online and offline techniques in downtown Beijing. The 24-h concentration of Pb was analyzed by ICP-MS while the number-count, particle size (in the range of 0.2-2 μm) and mixing state of Pb-containing particles were provided by Single Particle Aerosol Mass Spectrometry (SPAMS) with 1-h time resolution. In addition, the EI and Community Muti-Scale Air Quality (CMAQ) model were used to support the findings. The hourly Pb concentration simulated by CMAQ model was in good agreement with the Pb counts measured by SPAMS.
The Pb-containing particles sampled with SPAMS were classified into 3 major particle types: Pb mixed with secondary ions (68%), Pb mixed with carbonaceous compounds (18%), and Pb mixed with crustal compounds (14%). Primary emissions, assigned to sources such as coal combustion and dust, were in good agreement with the EI. On days with relatively low Pb counts, Pb-containing particles tended to be mixed with carbonaceous compounds, suggesting primary emissions sources such as coal combustion. During episodes with extremely high Pb counts, Pb-containing particles were more likely to be mixed with secondary inorganic species (nitrate and sulfate), suggesting a greater contribution from secondary formation and/or regional transport. Based on the single-particle analysis, about 64±18% of the daily Pb-containing particles in Beijing were from transported/aging process, which is comparable with that of CMAQ.