Dr. Yoshizumi Kajii, Professor

Dr. Yoshizumi Kajii

OH reactivity measurement by laser pump and probe technique and its application to diagnosis of air quality

Tokyo Metropolitan University

*The organization and the title are those when awarded

Abstract

  • 日本語
  • English

大気反応機構解明や大気質診断を行うために,反応性化学物質の網羅的観測を行う代わりに,OHラジカル反応性を測定することで同様の情報を引出す手法を提案した。OHラジカルをレーザーにより人工的に生成し,その減衰を測定することで対象としている試料の反応性物質の総量に相当する情報を得るという手法である。東京の郊外と都心部において,大気集中観測を実施したところ100種類もの化学成分ガスの同時測定を行ったが,OH反応性観測の結果25-50%もの未知なる反応性物質の存在が示唆された。未知なる反応性物質は,冬季以外に顕著に存在していることから,植物や自動車由来の一次発生源か,あるいは大気中で二次的に生成してくる化学物質である可能性が高い。

To reveal reaction mechanism of the atmosphere or diagnosis air quality we proposed a new methodology to get equivalent information of reactive species without systematic observation of all kinds of VOCs. We enhanced OH concentration in real atmosphere using pulse laser and measured the decay of OH using laser induced fluorescence technique. We successfully developed the system to measure OH reactivity using laser flash pump and probe technique. Using this instrument we observed both urban and semi-urban air with simultaneous analysis of reactive species. Interestingly systematic under estimation of OH reactivity was obtained. It ranged from 25 to 50 % of total OH reactivity depending on the season and also locations. It indicates a considerable amount of missing sink of OH that we do not consider yet even though we counted more than 100 kinds of chemical species.

Research summary

The study of Dr. Kajii focused on the quantitative determination of unidentified reactive trace chemical species by measuring the decay of artificially generated hydroxyl (OH) radicals. The proposed research has direct on the huge problem of automobile exhaust emissions.

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