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DOI	10.5194/acp-20-3333-2020
	Importance of isomerization reactions for OH radical regeneration from the photo-oxidation of isoprene investigated in the atmospheric simulation chamber SAPHIR
	Novelli A.; Vereecken L.; Bohn B.; Dorn H.-P.; Gkatzelis G.I.; Hofzumahaus A.; Holland F.; Reimer D.; Rohrer F.; Rosanka S.; Taraborrelli D.; Tillmann R.; Wegener R.; Yu Z.; Kiendler-Scharr A.; Wahner A.; Fuchs H.
发表日期	2020
ISSN	1680-7316
起始页码	3333
结束页码	3355
卷号	20 期号:6
英文摘要	Theoretical, laboratory, and chamber studies have shown fast regeneration of the hydroxyl radical (OH) in the photochemistry of isoprene, largely due to unimolecular reactions which were previously thought not to be important under atmospheric conditions. Based on early field measurements, nearly complete regeneration was hypothesized for a wide range of tropospheric conditions, including areas such as the rainforest where slow regeneration of OH radicals is expected due to low concentrations of nitric oxide (NO). In this work the OH regeneration in isoprene oxidation is directly quantified for the first time through experiments covering a wide range of atmospherically relevant NO levels (between 0.15 and 2 ppbv - parts per billion by volume) in the atmospheric simulation chamber SAPHIR. These conditions cover remote areas partially influenced by anthropogenic NO emissions, giving a regeneration efficiency of OH close to 1, and areas like the Amazonian rainforest with very low NO, resulting in a surprisingly high regeneration efficiency of 0.5, i.e. a factor of 2 to 3 higher than explainable in the absence of unimolecular reactions. The measured radical concentrations were compared to model calculations, and the best agreement was observed when at least 50% of the total loss of isoprene peroxy radicals conformers (weighted by their abundance) occurs via isomerization reactions for NO lower than 0.2 ppbv. For these levels of NO, up to 50% of the OH radicals are regenerated from the products of the 1,6 α-hydroxy-hydrogen shift (1,6-H shift) of Z-δ-RO2 radicals through the photolysis of an unsaturated hydroperoxy aldehyde (HPALD) and/or through the fast aldehydic hydrogen shift (rate constant ∼ 10 s-1 at 300 K) in di-hydroperoxy carbonyl peroxy radicals (di-HPCARP-RO2), depending on their relative yield. The agreement between all measured and modelled trace gases (hydroxyl, hydroperoxy, and organic peroxy radicals, carbon monoxide, and the sum of methyl vinyl ketone, methacrolein, and hydroxyl hydroperoxides) is nearly independent of the adopted yield of HPALD and di-HPCARP-RO2 as both degrade relatively fast (< 1 h), forming the OH radical and CO among other products. Taking into consideration this and earlier isoprene studies, considerable uncertainties remain on the distribution of oxygenated products, which affect radical levels and organic aerosol downwind of unpolluted isoprene-dominated regions. © Author(s) 2020.
语种	英语
scopus关键词	atmospheric chemistry; chemical composition; concentration (composition); hydroxyl radical; isoprene; nitric oxide; photochemistry; photooxidation; trace element; troposphere
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/247903
作者单位	Forschungszentrum Jülich, Institute for Energy and Climate Research: Troposphere (IEK-8), Jülich, 52425, Germany; NOAA Earth Systems Research Laboratory, Boulder, CO 80305, United States; Cooperative Institute for Research in Environmental Sciences, Boulder, CO 80309, United States; Institute of Mass Spectrometry and Atmospheric Environment, Jinan University, Guangzhou, 510632, China
推荐引用方式 GB/T 7714	Novelli A.,Vereecken L.,Bohn B.,et al. Importance of isomerization reactions for OH radical regeneration from the photo-oxidation of isoprene investigated in the atmospheric simulation chamber SAPHIR[J],2020,20(6).
APA	Novelli A..,Vereecken L..,Bohn B..,Dorn H.-P..,Gkatzelis G.I..,...&Fuchs H..(2020).Importance of isomerization reactions for OH radical regeneration from the photo-oxidation of isoprene investigated in the atmospheric simulation chamber SAPHIR.ATMOSPHERIC CHEMISTRY AND PHYSICS,20(6).
MLA	Novelli A.,et al."Importance of isomerization reactions for OH radical regeneration from the photo-oxidation of isoprene investigated in the atmospheric simulation chamber SAPHIR".ATMOSPHERIC CHEMISTRY AND PHYSICS 20.6(2020).