Medeiros, DJ, Blitz, MA orcid.org/0000-0001-6710-4021, Seakins, PW orcid.org/0000-0002-4335-8593 et al. (1 more author) (2022) Direct Measurements of Isoprene Autoxidation: Pinpointing Atmospheric Oxidation in Tropical Forests. Journal of the American Chemical Society, 2 (4). pp. 809-818. ISSN 0002-7863
Abstract
2-Methyl-1,3-butadiene (isoprene), released from biogenic sources, accounts for approximately a third of hydrocarbon emissions and is mainly removed by hydroxyl radicals, OH, the primary initiator of atmospheric oxidation. In situ measurements in clean tropical forests (high isoprene and low NOx) have measured OH concentrations up to an order of magnitude higher than model predictions, which impacts our understanding of global oxidation. In this study, direct, laser flash photolysis, laser-induced fluorescence measurements at elevated temperatures have observed OH recycling in the presence of isoprene and oxygen under conditions where interference from secondary or heterogeneous chemistry is minimal. Our results provide the first direct, time-resolved, experimental validation of the theory-based Leuven Isoprene Mechanism (LIM1), based on isomerization of isoprene-RO2 radicals and OH regeneration, that partially accounts for model:measurement divergence in OH. While our data can be fit with only minor alterations in important LIM1 parameters, and the overall rate of product formation is similar to LIM1, there are differences with the recent experimental study by Teng et al. J. Am. Chem. Soc.2017, 139, 5367–5377. In addition, our study indicates that the dihydroperoxide products are significantly enhanced over previous estimates. Dihydroperoxides are chemical and photochemical sources of OH, and the implications of enhanced hydroperoxide formation on the agreement between models and observations in tropical forests are examined.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | © 2022 The Authors. Published by American Chemical Society. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. |
Keywords: | kinetics, OH radical, isoprene, OH recycling, atmospheric chemistry, modeling |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Physical Chemistry (Leeds) |
Funding Information: | Funder Grant number NERC (Natural Environment Research Council) NE/K005820/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 07 Mar 2022 13:00 |
Last Modified: | 10 Jun 2022 19:24 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/jacsau.1c00525 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:184362 |