HR: 0800h
AN: A51E-0121    [Abstracts]
TI: Seasonal variation of the source contribution of atmospheric C₂-C₇ NMHCs (non-methanehydrocarbons) in central Tokyo
AU: * Shirai, T
EM: tshirai@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AU: Yokouchi, Y
EM: yokouchi@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AU: Kita, K
EM: kita@env.sci.ibaraki.ac.jp
AF: Ibaraki University, 2-1-1 Bunkyo, Mito, 310-8512 Japan
AU: Izumi, K
EM: izumi-k@eng.toyo.ac.jp
AF: Toyo University, 2100 Kujirai, Kawagoe, 350-8585 Japan
AU: Koike, M
EM: koike@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Science, University of Tokyo, 7-3-1, Bunkyo-ku, Tokyo, 113-0033 Japan
AU: Komazaki, Y
EM: komazaki@atmos.rcast.u-tokyo.ac.jp
AF: Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8904 Japan
AU: Fukuda, M
EM: fukuda@atmos.rcast.u-tokyo.ac.jp
AF: Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8904 Japan
AU: Kondo, Y
A51E-0121 AF: Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8904 Japan
AB: Seasonal change of the relative contribution of the sources of C₂-C₇ NMHCs has been investigated using the datasets obtained from the IMPACT (Integrated Measurement Program for Aerosol and Oxidant Chemistry in Tokyo) measurement campaigns conducted in downtown Tokyo in four different periods (19 July - 13 August and 2-15 October of 2003, 20 January - 6 February and 26 July - 14 August of 2004).
Among 18 compounds (7 alkanes, 8 alkenes, 1 alkyne, and 2 aromatics) measured during the campaigns, isoprene showed the distinct diurnal variation in summer. The mixing ratio of isoprene tightly correlated with solar flux and temperature measured at the observation site, indicating the local vegetation as its dominant source. In autumn and winter, no such correlation was observed and the atmospheric level of isoprene was 10 times lower than in summer.
To determine the relative contribution of major sources of NMHCs, Principal Component analyses has been applied to each dataset, which gave different result according to the season. In summer, the three components were figured out to have significant contribution; automotive exhaust, fuel evaporation, and photochemical production. On the contrary, no signature of evaporative emission and photochemical production was seen in autumn and winter. Measured NMHCs showed fairly good correlation with C₂H₂ (R²>0.6 except for C₃H₆) which is considered to be emitted exclusively from automotives in urban area, suggesting that the car exhaust is the dominant source of C₂-C₇ NMHCs in central Tokyo in winter.
Considering the composition observed in winter as the typical composition from automotive emission in central Tokyo, the contribution from other sources was estimate for summer composition. In result, 30-60% of C₄-C₅ alkanes, 70% of n-C₆H₁₄ and up to 50% of C₇H₈ were attributed to non-automotive emissions, most likely gasoline vapor and solvent use, respectively.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0322 Constituent sources and sinks
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005