Photoinduced formation of persistent free radicals, hydrogen radicals, and hydroxyl radicals from catechol on atmospheric particulate matter

• Published in: iScience Vol. 24; no. 3; p. 102193
• Main Authors: Qin, Linjun, Yang, Lili, Yang, Jiahui, Weber, Ralph, Ranguelova, Kalina, Liu, Xiaoyun, Lin, Bingcheng, Li, Cui, Zheng, Minghui, Liu, Guorui
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.03.2021; Elsevier
• Subjects: Chemistry; Environmental Chemical Engineering; Environmental Science; Theoretical Photochemistry; Chemistry; Environmental Science; Theoretical Photochemistry; Environmental Chemical Engineering
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2021.102193

Catechol is speculated to be a potential precursor of environmentally persistent free radicals (EPFRs) in the atmosphere. EPFRs absorbed on PM2.5 have attracted public attention because their toxicity is similar to cigarette smoke. In this study, we found that catechol could produce EPFRs, which were oxygen-centered phenoxy and semiquinone radicals. These free radical species had half-lives of up to 382 days. CaO, CuO, and Fe2O3 markedly promoted EPFR formation from catechol. The valence states of Cu and Fe changed during the photochemical reactions of catechol but no valence state changed for Ca. Alkaline nature of CaO is possibly the key for promoting the free radical formations through acid-base reactions with catechol. In addition to hydroxyl free radicals, hydrogen free radicals and superoxide anions formed from the photochemical reactions of catechol were first discovered. This is of concern because of the adverse effects of these free radicals on human health. [Display omitted] •Photochemical mechanism of persistent free radicals from catechol was clarified•Significant free radicals were formed via photochemical reactions of catechol••H and O2•− were first discovered from the photochemical reactions of catechol•This study is important for better recognizing DNA damage of air inhalation of PM2.5 Chemistry; Environmental Chemical Engineering; Theoretical Photochemistry; Environmental Science