HR: 08:36h
AN: A31E-03    [Abstracts]
TI: Diagnosis of Urban Air Quality by OH Ractivity Measurement
AU: * Kajii, Y J
EM: kajii@atmchem.apchem.metro-u.ac.jp
AF: Department of Applied Chemistry, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397 Japan
AU: Yoshino, A
EM: yoshino@atmchem.apchem.metro-u.ac.jp
AF: Department of Applied Chemistry, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397 Japan
AU: Kato, S
EM: shungo@atmchem.apchem.metro-u.ac.jp
AF: Department of Applied Chemistry, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397 Japan
AU: Sadanaga, Y
EM: sadanaga@chem.osakafu-u.ac.jp
AF: Department of Applied Chemistry, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397 Japan
AU: Sadanaga, Y
EM: sadanaga@chem.osakafu-u.ac.jp
AF: Department of Applied Chemistry, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka, 599-8531 Japan
AB: Measurements of OH reactivity provide very important information to verify our knowledge of atmospheric photochemistry. To realize this we developed an instrument to measure a lifetime of OH radical in ambient air by laser-induced pump and probe technique. OH radicals are generated in the photolysis of ozone by 266 nm laser. Decay of resultant OH is monitored by LIF-FAGE technique using 308 nm laser. Total OH reactivity which is inverse of lifetime was measured in the ambient air in Tokyo using the developed instrument in order to test the utility of the instrument. It demonstrated that the instrument is practically running well and we succeeded to observe OH reactivity through the year in Tokyo. To test our knowledge we have measured OH reaction partners as many as possible simultaneously. Calculated OH reactivity was obtained by the concentrations of NOx, CO, O3, NMHCs (non-methane hydrocarbons) and OVOCs (oxygenated volatile organic compounds) measured. In wintertime we found very nice agreement of OH reactivity between observed and calculated one. However, other seasons usually observed OH reactivities are higher than calculated during spring, summer, and fall. These suggest that the secondary products by the photochemical reactions in the atmosphere would be a missing sink for the OH loss process. The yield of peroxy radicals per an initially produced (ex. ozone photolysis) OH radical by the chain reactions is a very effective parameter to discuss ozone production in the urban atmosphere in terms of the air quality (i.e. the pollutant concentrations such as NOx, CO and VOCs). We defined this yield as the oxidant potential, Ψ. Since the oxidant potential is the yield of peroxy radicals per one OH radical by the chain reactions, Pozone, production rate of ozone is expressed as a product of initial concentration of OH and Ψ. We calculated Ψ values by simple box model in the case of including the unknown species as VOCs and excluding the missing sink, respectively. When the unknown species were included as VOCs, the potential increases from 32 % to 88 %. This result indicates the photochemical production rates of ozone in the urban air are substantially greater than expected. Finally we demonstrate that the measurement of OH reactivity in the urban atmosphere provides very useful information in order to diagnose comprehensively the urban air quality in terms oxidant formation.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0317 Chemical kinetic and photochemical properties
DE: 0322 Constituent sources and sinks
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005