Determination of Uptake Coefficient of Isoprene-Derived Organic Peroxy Radical onto Ambient Particles Using Laser Spectroscopic Techniques

• Published in: Journal of Japan Society for Atmospheric Environment / Taiki Kankyo Gakkaishi Vol. 58; no. 1; pp. 1 - 9
• Main Authors: Kajii, Yoshizumi, Li, Jiaru, Kohno, Nanase, Nakayama, Tomoki, Sato, Kei, Sakamoto, Yosuke
• Format: Journal Article
• Language: Japanese
• Published: Japan Society for Atmospheric Environment 10.01.2023; 公益社団法人 大気環境学会
• Subjects: isoprene; laser induced fluorescence; laser photolysis; photochemical oxidant; sodium chloride particles; versatile aerosol concentration enrichment system
• ISSN: 1341-4178; 2185-4335
• DOI: 10.11298/taiki.58.1

Although it has been suggested that the organic peroxy radical (RO2) uptake by ambient aerosols suppresses the ozone formation in the troposphere, atmospheric chemical model simulations often use a presumed uptake coefficient due to the lack of experimental values and the estimated suppression effect has remained unverified. In this study, we developed a method combining laser photolysis radical generation and laser induced fluorescence radical detection techniques (LP-LIF), and tested its performance to determine the uptake coefficient of RO2 onto particles. We succeeded in determining the uptake coefficients of ISOPOO, RO2 derived from the OH oxidation of isoprene onto standard NaCl particles to be 0.11±0.02. The dependence of the uptake coefficients on the particle surface and on the co-ion addition qualitatively corresponded to the model prediction, which validated the present method. Additionally, we connected a versatile aerosol concentration enrichment system (VACES) to LP-LIF and determined ISOPOO the uptake coefficient onto ambient aerosols to be 0.08±0.05 as an inverse-variance-weighted mean. Assuming all the RO2 have the same uptake coefficient to ISOPOO, a 2–9% suppression of the ozone formation rate by RO2 uptake was predicted under the clean sub-urban condition ([NOx] ~4 ppb, PM2.5 ~5 µg m−3). For a more accurate evaluation, improvement of the measurement precision and further investigation with other RO2 in the laboratory and atmospheric observations are required.