title: Contrasting diurnal variations in fossil and nonfossil secondary organic aerosol in urban outflow, Japan.
abstract: Diurnal variations of fossil secondary organic carbon (SOC) and nonfossil SOC were determined for the first time using a combination of several carbonaceous aerosol measurement techniques, including radiocarbon (¹⁴C) determinations by accelerator mass spectrometry, and a receptor model (chemical mass balance, CMB) at a site downwind of Tokyo during the summer of 2007. Fossil SOC showed distinct diurnal variation with a maximum during daytime, whereas diurnal variation of nonfossil SOC was relatively small. This behavior was reproduced by a chemical transport model (CTM). However, the CTM underestimated the concentration of anthropogenic secondary organic aerosol (ASOA) by a factor of 4-7, suggesting that ASOA enhancement during daytime is not explained by production from volatile organic compounds that are traditionally considered major ASOA precursors. This result suggests that unidentified semivolatile organic compounds or multiphase chemistry may contribute largely to ASOA production. As our knowledge of production pathways of secondary organic aerosol (SOA) is still limited, diurnal variations of fossil and nonfossil SOC in our estimate give an important experimental constraint for future development of SOA models.
authors.affiliation: National Institute for Environmental Studies, Ibaraki, Japan. morino.yu@nies.go.jp
authors.forename: Yu
authors.initials: Y
authors.lastname: Morino
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Takahashi
authors.forename: Akihiro
authors.initials: A
authors.lastname: Fushimi
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Tanabe
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Ohara
authors.forename: Shuichi
authors.initials: S
authors.lastname: Hasegawa
authors.forename: Masao
authors.initials: M
authors.lastname: Uchida
authors.forename: Akinori
authors.initials: A
authors.lastname: Takami
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yokouchi
authors.forename: Shinji
authors.initials: S
authors.lastname: Kobayashi
mesh_terms: D000336:Aerosols / Q000032:analysis* / Q000737:chemistry; D000392:Air Movements; D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D002244:Carbon / Q000032:analysis* / Q000737:chemistry; D002940:Circadian Rhythm; D002947:Cities; D004784:Environmental Monitoring / Q000379:methods; D005579:Fossil Fuels / Q000032:analysis*; D007564:Japan; D007700:Kinetics; D008956:Models, Chemical
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D005579:Fossil Fuels; D002244:Carbon