Measurements of OH and HO2 concentrations during the MCMA-2006 field campaign - Part 1: Deployment of the Indiana University laser-induced fluorescence
Name
Dusanter-2009-Measurements of OH and HO2 concentrations during the.pdf
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Author(s)
Dusanter, S.
Vimal, D.
Stevens, P. S.
Molina, Luisa Tan
Volkamer, R. A.
Date Issued
March 2009
Journal
Atmospheric Chemistry and Physics
Publisher
Copernicus Publications on behalf of the European Geosciences Union
Citation
Dusanter, S. et al. "Measurements of OH and HO2 concentrations during the MCMA-2006 field campaign – Part 1: Deployment of the Indiana University laser-induced fluorescence instrument." Atmos. Chem. Phys., 9, 1665–1685, 2009.
Version
Final published version
Abstract
Measurements of tropospheric hydroxyl (OH) and
hydroperoxy (HO2) radicals were made during the MCMA
(Mexico City Metropolitan Area) field campaign as part of
the MILAGRO (Megacity Initiative: Local and Global Research
Observations) project during March 2006. These radicals
were measured using a laser-induced fluorescence instrument
developed at Indiana University. This new instrument
takes advantage of the Fluorescence Assay by Gas Expansion
technique (FAGE) together with direct excitation
and detection of OH at 308 nm. HO2 is indirectly measured
as OH by titration with NO inside the fluorescence cell. At
this stage of development, IU-FAGE is capable of detecting
3.9×105 molecule/cm3 of both OH and HO2, with a signal
to noise ratio of 1, an averaged laser power of 10-mW and
an averaging time of 5-min. The calibration accuracies (1 omega)
are ±17% for OH and ±18% for HO2 using the water-vapor
photolysis/O2 actinometry calibration technique. OH and HO2 concentrations were successfully measured
at an urban site in Mexico City, with observed concentrations
comparable to those measured in other polluted environments.
Enhanced levels of OH and HO2 radicals were
observed on several days between 09:30–11:00 a.m. and suggest
an intense photochemistry during morning hours that
may be due to elevated sources of HOx (OH+HO2) and a fast
cycling between the radicals under the high NOx (NO+NO2)
conditions of the MCMA.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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DOI of Published Version
http://www.atmos-chem-phys.org/9/1665/2009/acp-9-1665-2009.pdf
