Spatial and Seasonal Variability of Aerosol Organic Mass-to-Organic Carbon Ratios in Chinese Cities
Organic aerosols constitute a key component of atmospheric fine particles, impacting air quality, public health, and climate. The aerosol organic mass-to-organic carbon (OM/OC) value is an important parameter often used to estimate total aerosol organic mass (OM) from organic carbon (OC) measurements. It contains critical information about the chemical composition of organic aerosol, which in turn affects its hygroscopic properties .We calculate the OM/OC values for Chinese urban aerosols from PM2.5 filter samples collected in winter and summer of 2003 in 14 Chinese cities. Two methods are used for the analysis. The first is a mass balance method, in which the organic mass is calculated as the difference between total aerosol mass and the mass sum of the other major species, including sulfate, nitrate, ammonium, elemental carbon and trace elements. OC measurement follows the IMPROVE thermal/Optical reflectance protocol. With this method we find averaged OM/OC values of 1.83 in winter and 1.90 in summer. The second method is based on the chemical structures of recognized organic compounds extracted with dichloromethane/methanol and water from the PM2.5 samples. Base on this method, we calculate averaged OM/OC values of 1.59 in winter and 1.75 in summer, indicating stronger photochemical oxidation in summer. Further studies show that oxalic acid has the greatest impact on OM/OC in summer and winter, since excluding it will decrease the local OM/OC significantly. Subsequently levoglucosan in winter and fatty acid, bis(2-ethylhexyl) phthalate(C24H38O4) in summer affect OM/OC significantly. Oxalic acid and Zn has the greatest correlation in summer, indicating that the source of oxalic acid is mostly anthropogenic.
OM/OC organic aerosols oxalic acid
Li Xing Tzung-May Fu Junji Cao Gehui Wang Kin Fai Ho Shun-cheng Lee Tijian Wang
Department of Atmospheric and Oceanic Sciences and Laboratory for Climate and Ocean-Atmosphere Studi Department of Atmospheric and Oceanic Sciences and Laboratory for Climate and Ocean-Atmosphere Studi State Key Laboratory of Loess and Quaternary Geology,Institute ofEarth Environment,Chinese Academy o Research Center of Urban Environmental Technology and Management,Department of Civil and Structural School of Atmospheric Sciences,Nanjing University,No.22 Hankou Road,Gulou District,Nanjing,China 21
国际会议
西安
英文
641-649
2011-08-17(万方平台首次上网日期,不代表论文的发表时间)