HR: 16:00h
AN: A22G-01    [PDF]
TI: Direct Detection of OH reactivity in the Urban Atmosphere by Laser Induced Pump and Probe Technique
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: Kato, S
EM: shungo@atmchem.apchem.metro-u.ac.jp
AF: Japan Science and Technology Corporation, Kawaguchi Center Building 4-1-8, Honcho, Kawaguchi, Saitama, 332-0012 Japan
AU: Matsumoto, J
EM: mjun@atmchem.apchem.metro-u.ac.jp
AF: Department of Applied Chemistry, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397 Japan
AU: Matsumoto, J
EM: mjun@atmchem.apchem.metro-u.ac.jp
AF: Japan Science and Technology Corporation, Kawaguchi Center Building 4-1-8, Honcho, Kawaguchi, Saitama, 332-0012 Japan
AU: Sadanaga, Y
EM: sadanaga@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@atmchem.apchem.metro-u.ac.jp
AF: Japan Science and Technology Corporation, Kawaguchi Center Building 4-1-8, Honcho, Kawaguchi, Saitama, 332-0012 Japan
AB: In order to test the theory of photochemical reaction in urban atmosphere HO$_x$ radicals (OH, HO$_2$, RO$_2$) that are usually difficult to detect due to both high reactivity and small abundance should be essentially measured. Monitoring technologies for these radicals in the ambient air are advanced recently with enough sensitivity by use of laser induced fluorescence (LIF) technique. Even though highly important information about atmospheric photochemistry can be provided by the absolute concentration of radicals, production and loss processes of these intermediate species cannot be discussed separately under the steady state condition. In case of urban atmosphere OH radical is considered to react with more than several hundreds of VOC as well as NO$_x$, SO$_2$, CO and Ozone. A measurement system of OH lifetime in the atmosphere was newly developed by a laser flash photolysis/chemical perturbation method. Ambient air is introduced into a flow tube and OH radicals are generated by a pump laser (266nm) in the photolysis of O$_3$. Concentration change of OH radicals generated by the pump laser is monitored by a probe laser (308 nm) using laser induced florescence technique. The decay rates of zero air where most of OH reaction partners were removed by Hot Pt oven and filters were measured with known amount of CO to obtain second-order rate coefficient of OH with CO. Resultant value agreed excellently with the previous reported value. OH reactivity was measured in the real atmosphere sampled at our campus where is considered as semi-urban area. Unexpected short lifetimes of OH were obtained. They ranged from 10 to 50 msec. In order to explain these short lifetimes of OH radicals several reaction partners were also measured simultaneously. Contributions of each reaction partners for OH radical removal will be discussed in this presentation.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0317 Chemical kinetic and photochemical properties
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting