AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Chemical and Optical Properties of Carbonaceous Aerosol in China
MEI ZHENG, Caiqing Yan, Jing Cai, Xiaoying Li, Yanjun Zhang, Peking University
Abstract Number: 392 Working Group: Haze in China: Sources, Formation Mechanisms, and Current Challenges
Abstract The strong correlation between high concentrations of PM$_(2.5) with low visibility has been found in cities in China where haze episodes occur. Sources of carbonaceous aerosol can be classified into two major source types based on the $^(14)C analysis (fossil and modern source). A few methods are combined in order to confirm and quantify the importance of fossil carbon in megacities in China (Beijing and Shanghai). The $^(14)C method provides quantitative estimate of contribution from modern and fossil source to organic carbon and water-soluble organic carbon (WSOC). During winter, about 75% to WIOC (water-insoluble organic carbon) and about 50% of WSOC are due to fossil source in Beijing. Low-temperature residential coal combustion is non-negligible during the colder season in this region. Functional groups of organic aerosol can be identified by Fourier-transform infrared transmission spectroscopy (FTIR). The contribution from aromatic CH in Beijing is much higher than that observed in samples in the U.S., where aromatic CH is rarely reported due to its low concentration. The high aromatic CH in the Beijing samples indicates the importance of anthropogenic sources in Beijing.
Therefore, carbonaceous aerosol in China is not only often associated with much higher concentration, but also higher fraction of anthropogenic sources. The light absorption of water-soluble organic carbon is measured. The spatial and temporal analyses show that the highest light absorption of WSOC is found in Beijing during winter. The comparison with chemical and optical properties of Chinese coal samples from source tests indicates that coal is an important contributor to brown carbon in Beijing during winter. A single particle aerosol mass spectrometer (SPAMS) is used to identify the mixing state of BC and the relationship with its optical properties is also examined. This presentation aims to identify several unique characteristics of carbonaceous aerosol in megacities in China compared to other countries such as the United States. These characteristics includes sources, light absorption, mixing state, etc.
Keywords: Carbonaceous Aerosol, Sources, Chemical and Optical Properties, Megacities, China