title: Sources of primary and secondary organic aerosol and their diurnal variations.
abstract: PM(2.5), as one of the criteria pollutants regulated in the U.S. and other countries due to its adverse health impacts, contains more than hundreds of organic pollutants with different sources and formation mechanisms. Daytime and nighttime PM2.5 samples from the August Mini-Intensive Gas and Aerosol Campaign (AMIGAS) in the southeastern U.S. were collected during summer 2008 at one urban site and one rural site, and were analyzed for organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), and various individual organic compounds including some important tracers for carbonaceous aerosol sources by gas chromatography-mass spectrometry. Most samples exhibited higher daytime OC concentration, while higher nighttime OC was found in a few events at the urban site. Sources, formation mechanisms and composition of organic aerosol are complicated and results of this study showed that it exhibited distinct diurnal variations. With detailed organic tracer information, sources contributing to particulate OC were identified: higher nighttime OC concentration occurring in several occasions was mainly contributed by the increasing primary emissions at night, especially diesel exhaust and biomass burning; whereas sources responsible for higher daytime OC concentration included secondary organic aerosol (SOA) formation (e.g., cis-pinonic acid and non-biomass burning WSOC) together with traffic emissions especially gasoline engine exhaust. Primary tracers from combustion related sources such as EC, polycyclic aromatic hydrocarbons, and hopanes and steranes were significantly higher at the urban site with an urban to rural ratio between 5 and 8. However, this urban-rural difference for secondary components was less significant, indicating a relatively homogeneous distribution of SOA spatially. We found cholesterol concentrations, a typical tracer for meat cooking, were consistently higher at the rural site especially during the daytime, suggesting the likely additional sources for this tracer at rural site and that it should be used with caution as meat cooking tracer in rural areas in the future.
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China; School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA. Electronic address: mzheng@pku.edu.cn.
authors.forename: Mei
authors.initials: M
authors.lastname: Zheng
authors.affiliation: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA.
authors.forename: Xiuying
authors.initials: X
authors.lastname: Zhao
authors.affiliation: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
authors.forename: Caiqing
authors.initials: C
authors.lastname: Yan
authors.affiliation: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA.
authors.forename: Wenyan
authors.initials: W
authors.lastname: Shi
authors.affiliation: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA.
authors.forename: Xiaolu
authors.initials: X
authors.lastname: Zhang
authors.affiliation: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA.
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Weber
authors.affiliation: University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Schauer
authors.affiliation: Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
authors.forename: Xinming
authors.initials: X
authors.lastname: Wang
authors.affiliation: Atmospheric Research & Analysis, Inc., Cary, NC 27513, USA.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Edgerton
mesh_terms: D000336:Aerosols; D000397:Air Pollution / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry; D009930:Organic Chemicals / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis*
chemical_list: D000336:Aerosols; D009930:Organic Chemicals; D052638:Particulate Matter
keywords: Diurnal variation; Organic aerosol; Primary and secondary sources; Source apportionment