Hansen, RF, Lewis, TR, Graham, L et al. (4 more authors) (2017) OH Production from the Photolysis of Isoprene-derived Peroxy Radicals: Cross-sections, quantum yields and atmospheric implications. Physical Chemistry Chemical Physics, 19 (3). pp. 2332-2345. ISSN 1463-9076
Abstract
In environments with high concentrations of biogenic volatile organic compounds and low concentrations of nitrogen oxides (NOx = NO + NO2), significant discrepancies have been found between measured and modeled concentrations of hydroxyl radical (OH). The photolysis of peroxy radicals from isoprene (HO-Iso-O2) in the near ultraviolet represents a potential source of OH in these environments, yet has not been considered in atmospheric models. This paper presents measurements of the absorption cross-sections for OH formation (σRO2,OH) from the photolysis of HO-Iso-O2 at wavelengths from 310–362.5 nm via direct observation by laser-induced fluorescence of the additional OH produced following laser photolysis of HO-Iso-O2. Values of σRO2,OH for HO-Iso-O2 ranged from (6.0 ± 1.6) × 10-20 cm2 molecule-1 at 310 nm to (0.5 ± 0.15) × 10-20 cm2 molecule-1 at 362.5 nm. OH photodissociation yields from HO-Iso-O2 photolysis, ϕOH,RO2, were determined via comparison of the measured values of σRO2,OH to the total absorption cross-sections for HO-Iso-O2 (σRO2), which were obtained using a newly-constructed spectrometer. ϕOH,RO2 was determined to be 0.13 ± 0.037 at wavelengths from 310–362.5 nm. To determine the impact of HO-Iso-O2 photolysis on atmospheric OH concentrations, a modeling case-study for a high-isoprene, low-NOx environment (namely, the 2008 Oxidant and Particle Photochemical Processes above a South-East Asian Tropical Rainforest (OP-3) field campaign, conducted in Borneo) was undertaken using the detailed Master Chemical Mechanism. The model calculated that the inclusion of HO-Iso-O2 photolysis in the model had increased the OH concentration by only 1% on average from 10:00–16:00 local time. Thus, HO-Iso-O2 photolysis alone is insufficient to resolve the discrepancy seen between measured OH concentrations and those predicted by atmospheric chemistry models in such environments.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © the Owner Societies 2017. This is an author produced version of a paper published in Physical Chemistry Chemical Physics . Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Physical Chemistry (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 15 Dec 2016 12:20 |
Last Modified: | 12 Dec 2017 01:38 |
Published Version: | https://doi.org/10.1039/C6CP06718B |
Status: | Published |
Publisher: | Royal Society of Chemistry |
Identification Number: | 10.1039/C6CP06718B |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:109481 |