HR: 0830h
AN: A11F-0049    [PDF]
TI: In-situ Measurement of Atmospheric NO$_{3}$ Radical by Laser-Induced Fluorescence Technique
AU: * Matsumoto, J
EM: mjun@atmchem.apchem.metro-u.ac.jp
AF: Dept. of Applied Chem., Tokyo Metropolitan Univ., 1-1 Minami-Osawa, Hachioji, Tokyo, 1920397 Japan
AU: * Matsumoto, J
EM: mjun@atmchem.apchem.metro-u.ac.jp
AF: Japan Sci. and Tech. Corp., 4-1-8 Honcho, Kawaguchi, Saitama, 3320012 Japan
AU: Imai, H
EM: k-dub@atmchem.apchem.metro-u.ac.jp
AF: Dept. of Applied Chem., Tokyo Metropolitan Univ., 1-1 Minami-Osawa, Hachioji, Tokyo, 1920397 Japan
AU: Kosugi, N
EM: knaohiro@atmchem.apchem.metro-u.ac.jp
AF: Dept. of Applied Chem., Tokyo Metropolitan Univ., 1-1 Minami-Osawa, Hachioji, Tokyo, 1920397 Japan
AU: Kajii, Y
EM: kajii@atmchem.apchem.metro-u.ac.jp
AF: Dept. of Applied Chem., Tokyo Metropolitan Univ., 1-1 Minami-Osawa, Hachioji, Tokyo, 1920397 Japan
AB: Nitrate radical (NO$_{3}$) plays critical roles in the nighttime atmosphere. NO$_{3}$ is important as an intermediate in the NOx loss process. In addition, NO$_{3}$ can oxidize various tracers like hydrocarbons and generate peroxy radicals at night. The abundance of NO$_{3}$ is very small, at the level of pptv, due to its high reactivity. Temporal and spatial variability of NO$_{3}$ is large. Thus, sensitive, fast, in-situ measurement of NO$_{3}$ is essential. However, there are few techniques which can satisfy all requirements. In this study, a new laser-induced fluorescence (LIF) instrument for measuring NO$_{3}$ has been developed and improved. As the excitation light, the laser beam from a dye laser pumped by an SHG of Nd:YVO$_{4}$ laser (7 W, 10 kHz) is utilized. Typical output of the laser was 600 mW at 623 nm where the absorption spectrum of NO$_{3}$ has a peak. The sample air was introduced into the excitation cell at the pressure of $\sim$ 2 Torr. The red-shifted fluorescence emitted from the excited NO$_{3}$ was detected by a cooled photomultiplier. Optimization of the instrument was conducted for various settings and configurations. Specifications of the instrument were explored for two standard samples: (a) NO$_{3}$ formation from NOx oxidation by O$_{3}$, (b) NO$_{3}$ formation from thermal decomposition of N$_{2}$O$_{5}$ and then conversion to NO$_{2}$ by NO addition. As a result, good agreement between these two methods of NO$_{3}$ formation was confirmed. Finally, the sensitivity and background were 0.24 cps ppbv$^{-1}$ mW$^{-1}$ and 0.20 cps mW$^{-1}$, respectively. The limit of detection was estimated as 4 pptv for {\it S/N} = 1 and 10-min averaging. Thus, the instrument has sufficient potential to detect nighttime NO$_{3}$ in the atmosphere. As a next step, field test of the instrument will be carried out. The LIF-NO$_{3}$ instrument is promising for research on nighttime chemistry in near future.
UR: http://atmchem.apchem.metro-u.ac.jp/~mjun/agu03/
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