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[B-4.1 Studies on Photochemical Reaction Mechanism of Greenhouse Gases and Related Gases in the Atmosphere]

[Contact Person]

Nobuaki Washida
Director, Atmospheric Environmental Division
National Institute for Environmental Studies
Environmental Agency
16-2 Onogawa, Tsukuba, Ibaraki 305 Japan
Phone +81-298-51-6111 (Ext.350), Fax +81-298-51-4732

[Total Budget for FY1990-1992]

23,133,000 Yen

[Abstract]

For the purpose of obtaining the basic data to estimate the emission rate of CO from the photooxidation of natural hydrocarbons terpenes in the atmosphere, OH radical-initiated photooxidation of isoprene and terpenes have been investigated experimentally by a 6-m³ photochemical reaction chamber equipped with a long path length FTIR spectrometer. In the absence of NOx, the reaction mechanism was found to be quite different from that in the presence of NOx and major reaction products appeared in the infrared spectra were attributed to organic hydroperoxides. The CO yield from the reaction of OH with isoprene in the real atmosphere was evaluated as 39% on the carbon number basis and global annual CO production from isoprene was estimated to be 133 Tg C yr^-1. Gross annual emission of CO from the reactions of OH with terpenes was estimated to be 22 Tg C yr^-1 (50 Tg CO yr^-1) by regarding α-pinene as the representative terpenes. The ultimate yield of CO from the tropospheric oxidation of terpenes (including both ozone and OH reactions) was estimated to be 20 % on the carbon number basis, and the total annual emission of CO was evaluated to be 96 Tg C yr^-1 (222 Tg CO yr^-1). In Consequence, global CO production from natural hydrocarbons was evaluated to be 229 Tg C yr^-1

[Key Words]

Isoprene, Terpene, α-pinene, CO Production, CFC Alternative