Journal cover Journal topic
Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 3.248 IF 3.248
  • IF 5-year value: 3.650 IF 5-year 3.650
  • CiteScore value: 3.37 CiteScore 3.37
  • SNIP value: 1.253 SNIP 1.253
  • SJR value: 1.869 SJR 1.869
  • IPP value: 3.29 IPP 3.29
  • h5-index value: 47 h5-index 47
  • Scimago H index value: 60 Scimago H index 60
Volume 9, issue 8 | Copyright
Atmos. Meas. Tech., 9, 3851-3861, 2016
https://doi.org/10.5194/amt-9-3851-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 19 Aug 2016

Research article | 19 Aug 2016

A new technique for the direct detection of HO2 radicals using bromide chemical ionization mass spectrometry (Br-CIMS): initial characterization

Javier Sanchez1, David J. Tanner2, Dexian Chen2, L. Gregory Huey2, and Nga L. Ng1,2 Javier Sanchez et al.
  • 1School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
  • 2School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA

Abstract. Hydroperoxy radicals (HO2) play an important part in tropospheric photochemistry, yet photochemical models do not capture ambient HO2 mixing ratios consistently. This is likely due to a combination of uncharacterized chemical pathways and measurement limitations. The indirect nature of current HO2 measurements introduces challenges in accurately measuring HO2; therefore a direct technique would help constrain HOx chemistry in the atmosphere. In this work we evaluate the feasibility of using chemical ionization mass spectrometry (CIMS) and propose a direct HO2 detection scheme using bromide as a reagent ion. Ambient observations were made with a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) in Atlanta over the month of June 2015 to demonstrate the capability of this direct measurement technique. Observations displayed expected diurnal profiles, reaching daytime median values of ∼ 5ppt between 2 and 3p.m. local time. The HO2 diurnal profile was found to be influenced by morning-time vehicular NOx emissions and shows a slow decrease into the evening, likely from non-photolytic production, among other factors. Measurement sensitivities of approximately 5.1±1.0cpsppt−1 for a bromide ion (79Br) count rate of 106cps were observed. The relatively low instrument background allowed for a 3σ lower detection limit of 0.7ppt for a 1min integration time. Mass spectra of ambient measurements showed the 79BrHO2 peak was the major component of the signal at nominal mass-to-charge 112, suggesting high selectivity for HO2 at this mass-to-charge. More importantly, this demonstrates that these measurements can be achieved using instruments with only unit mass resolution capability.

Publications Copernicus
Download
Short summary
HO2 radicals play an important role in tropospheric chemistry. Here we propose a new direct method for measuring HO2 radicals in the atmosphere using bromide anion chemical ionization mass spectrometry. Ambient measurements in Atlanta are presented. Instrument performance parameters: sensitivity, lower detection limit, and time resolution are discussed. We demonstrate that the technique provides excellent selectivity and is suitable for in situ ground-based HO2 measurements.
HO2 radicals play an important role in tropospheric chemistry. Here we propose a new direct...
Citation
Share