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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 1 | Copyright
Atmos. Meas. Tech., 11, 1-16, 2018
https://doi.org/10.5194/amt-11-1-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 03 Jan 2018

Research article | 03 Jan 2018

Measurements of a potential interference with laser-induced fluorescence measurements of ambient OH from the ozonolysis of biogenic alkenes

Pamela Rickly1 and Philip S. Stevens1,2 Pamela Rickly and Philip S. Stevens
  • 1School of Public and Environmental Affairs, Indiana, University, Bloomington, IN, USA
  • 2Department of Chemistry, Indiana University, Bloomington, IN, USA

Abstract. Reactions of the hydroxyl radical (OH) play a central role in the chemistry of the atmosphere, and measurements of its concentration can provide a rigorous test of our understanding of atmospheric oxidation. Several recent studies have shown large discrepancies between measured and modeled OH concentrations in forested areas impacted by emissions of biogenic volatile organic compounds (BVOCs), where modeled concentrations were significantly lower than measurements. A potential reason for some of these discrepancies involves interferences associated with the measurement of OH using the laser-induced fluorescence–fluorescence assay by gas expansion (LIF-FAGE) technique in these environments. In this study, a turbulent flow reactor operating at atmospheric pressure was coupled to a LIF-FAGE cell and the OH signal produced from the ozonolysis of α-pinene, β-pinene, ocimene, isoprene, and 2-methyl-3-buten-2-ol (MBO) was measured. To distinguish between OH produced from the ozonolysis reactions and any OH artifact produced inside the LIF-FAGE cell, an external chemical scrubbing technique was used, allowing for the direct measurement of any interference. An interference under high ozone (between 2 × 1013 and 10 × 1013cm−3) and BVOC concentrations (between approximately 0.1 × 1012 and 40 × 1012cm−3) was observed that was not laser generated and was independent of the ozonolysis reaction time. For the ozonolysis of α- and β-pinene, the observed interference accounted for approximately 40% of the total OH signal, while for the ozonolysis of ocimene the observed interference accounted for approximately 70% of the total OH signal. Addition of acetic acid to the reactor eliminated the interference, suggesting that the source of the interference in these experiments involved the decomposition of stabilized Criegee intermediates (SCIs) inside the FAGE detection cell. Extrapolation of these measurements to ambient concentrations suggests that these interferences should be below the detection limit of the instrument.

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The hydroxyl radical is the primary atmospheric oxidant in the atmosphere, and measurements of its concentration provide a rigorous test of our understanding of atmospheric chemistry. This paper presents measurements of a potential interference with measurements of OH using laser-induced fluorescence techniques, which may contribute to measurements of OH in forested environments. The results may help to explain discrepancies between measurements and model predictions in these environments.
The hydroxyl radical is the primary atmospheric oxidant in the atmosphere, and measurements of...
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