气候变化领域集成服务门户(CCPortal): Halogen activation and radical cycling initiated by imidazole-2-carboxaldehyde photochemistry

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DOI	10.5194/acp-19-10817-2019
	Halogen activation and radical cycling initiated by imidazole-2-carboxaldehyde photochemistry
	Corral Arroyo P.; Aellig R.; Alpert P.A.; Volkamer R.; Ammann M.
发表日期	2019
ISSN	16807316
起始页码	10817
结束页码	10828
卷号	19 期号:16
英文摘要	Atmospheric aerosol particles can contain light-absorbing organic compounds, also referred to as brown carbon (BrC). The ocean surface and sea spray aerosol particles can also contain light-absorbing organic species referred to as chromophoric dissolved organic matter (CDOM). Many BrC and CDOM species can contain carbonyls, dicarbonyls or aromatic carbonyls such as imidazole-2-carboxaldehyde (IC), which may act as photosensitizers because they form triplet excited states upon UV-VIS light absorption. These triplet excited states are strong oxidants and may initiate catalytic radical reaction cycles within and at the surface of atmospheric aerosol particles, thereby increasing the production of condensed-phase reactive oxygen species (ROS). Triplet states or ROS can also react with halides, generating halogen radicals and molecular halogen compounds. In particular, molecular halogens can be released into the gas phase, which is one halogen activation pathway. In this work, we studied the influence of bromide and iodide on the photosensitized production and release of hydroperoxy radicals (HO2) upon UV irradiation of films in a coated wall flow tube (CWFT) containing IC in a matrix of citric acid (CA) irradiated with UV light. In addition, we measured the iodine release upon irradiation of IC/CA films in the CWFT. We developed a kinetic model coupling photosensitized CA oxidation with condensed-phase halogen chemistry to support data analysis and assessment of atmospheric implications in terms of HO2 production and halogen release in sea spray particles. As indicated by the experimental results and confirmed by the model, significant recycling of halogen species occurred via scavenging reactions with HO2. These prevented the full and immediate release of the molecular halogen (bromine and iodine) produced. Recycling was stronger at low relative humidity, attributed to diffusion limitations. Our findings also show that the HO2 production from BrC or CDOM photosensitized reactions can increase due to the presence of halides, leading to high HO2 turnover, in spite of low release due to the scavenging reactions. We estimated the iodine production within sea salt aerosol particles due to iodide oxidation by ozone (O3) at 5.0 × 10-6 Ms-1 assuming O3 was in Henry's law equilibrium with the particle. However, using an O3 diffusion coefficient of 1 × 10-12 cm2 s-1, iodine activation in an aged, organic-rich sea spray is estimated to be 5.5 × 10-8 Ms-1. The estimated iodine production from BrC photochemistry based on the results reported here amounts to 4.1 × 10-7 Ms-1 and indicates that BrC photochemistry can exceed O3 reactive uptake in controlling the rates of iodine activation from sea spray particles under dry or cold conditions where diffusion is slow within particles. © Author(s) 2019.
语种	英语
scopus关键词	aerosol; atmospheric chemistry; brown carbon; concentration (composition); dissolved organic matter; halogen; hydroxyl radical; photochemistry
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/144192
作者单位	Paul Scherrer Institute, Laboratory of Environmental Chemistry, Villigen PSI, 5232, Switzerland; Department of Chemistry and Biochemistry, University of Bern, Bern, 2012, Switzerland; ETH Swiss Federal Institute of Technology Zürich, Institute for Atmospheric and Climate Science, Zurich, 8006, Switzerland; Department of Chemistry, UCB, University of Colorado, Boulder, CO 80309, United States; Cooperative Institute for Research in Environmental Sciences (CIRES), UCB, University of Colorado, Boulder, CO 80309, United States
推荐引用方式 GB/T 7714	Corral Arroyo P.,Aellig R.,Alpert P.A.,et al. Halogen activation and radical cycling initiated by imidazole-2-carboxaldehyde photochemistry[J],2019,19(16).
APA	Corral Arroyo P.,Aellig R.,Alpert P.A.,Volkamer R.,&Ammann M..(2019).Halogen activation and radical cycling initiated by imidazole-2-carboxaldehyde photochemistry.Atmospheric Chemistry and Physics,19(16).
MLA	Corral Arroyo P.,et al."Halogen activation and radical cycling initiated by imidazole-2-carboxaldehyde photochemistry".Atmospheric Chemistry and Physics 19.16(2019).