AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Sources of PM2.5 during Haze Episodes in Winter 2016 in Beijing
MEI ZHENG, Caiqing Yan, Tian Zhou, Yue Liu, Xuhui Cai, Jie Li, Peking University
Abstract Number: 489 Working Group: Aerosol Chemistry
Abstract Beijing has implemented various emission controls especially in the past several years. However, Beijing and some other cities in the North China Plain experienced more severe haze episodes in November and December 2016, when higher average PM2.5 concentration was found than the previous year. High-time resolution (1-h) measurements of PM2.5 composition were performed continuously from November to December 2016, including PM2.5 mass by TEOM, EC and OC by Sunset semi-continuous OC/EC analyzer, major ions by in-situ Gas and Aerosol Compositions Monitor (IGAC), and multiple metals by Xact. The detailed chemical speciation data were integrated with meteorological data such as wind speed and direction as well as footprint results to identify regional transport and potential source regions of fine particles measured in Beijing. Our results indicated that there was a clear cycle of PM2.5 concentrations with a period of about a few days (less than 10 days). The lowest concentrations were all occurred during a strong cold front from northwest, with very similar chemical composition (sulfate accounting for about 40% of PM2.5 and the relative abundance of Ca higher than other periods). During the later stage of haze, higher secondary inorganic species dominated PM2.5 in Beijing, with both local and regional contributions. During the most severe and longest episode during the study period, carbonaceous aerosol and trace metals did not exhibit increase while secondary inorganics continued to increase. Sources of PM2.5 were identified with receptor models using positive matrix factorization (PMF). It was found that poorer dispersion conditions in winter 2016 also contributed to higher PM2.5 concentrations compared to winter 2015. This study combined high-time resolution chemical speciation data with footprint results and meteorological information to explain major source types and regions that contributed to high PM2.5 measured in Beijing.