1School of Public and Environmental Affairs, Indiana University, Bloomington, IN, USA
2Center for Research in Environmental Science, Indiana University, Bloomington, IN, USA
3Department of Chemistry, Indiana University, Bloomington, IN, USA
4Université Lille Nord de France, 59000, Lille, France
5Mines Douai, CE, F59508, Douai, France
6Department of Chemistry, Purdue University, West Lafayette, IN, USA
7Department of Chemistry, Western Michigan University, Kalamazoo, MI, USA
8Department of Chemistry, University of Michigan, Ann Arbor, MI, USA
9Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI, USA
10Department of Civil and Environmental Engineering, Washington State University, Pullman, WA, USA
11Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
12Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, USA
13School of Public Health, State University of New York at Albany, Albany, NY, USA
14Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
15Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN, USA
*now at: Department of Chemistry and Biochemistry, University of San Diego, San Diego, CA, USA
**now at: School of Public and Environmental Affairs, Indiana University, Bloomington, IN, USA
***now at: Civil and Environmental Engineering, Princeton University, Princeton, NJ, USA
Received: 06 Nov 2012 – Discussion started: 20 Dec 2012
Abstract. Hydroxyl (OH) and hydroperoxyl (HO2) radicals are key species driving the oxidation of volatile organic compounds that can lead to the production of ozone and secondary organic aerosols. Previous measurements of these radicals in forest environments with high isoprene, low NOx conditions have shown serious discrepancies with modeled concentrations, bringing into question the current understanding of isoprene oxidation chemistry in these environments.
Revised: 25 Apr 2013 – Accepted: 03 May 2013 – Published: 03 Jun 2013
During the summers of 2008 and 2009, OH and peroxy radical concentrations were measured using a laser-induced fluorescence instrument as part of the PROPHET (Program for Research on Oxidants: PHotochemistry, Emissions, and Transport) and CABINEX (Community Atmosphere-Biosphere INteractions EXperiment) campaigns at a forested site in northern Michigan. Supporting measurements of photolysis rates, volatile organic compounds, NOx (NO + NO2 and other inorganic species were used to constrain a zero-dimensional box model based on the Regional Atmospheric Chemistry Mechanism, modified to include the Mainz Isoprene Mechanism (RACM-MIM). The CABINEX model OH predictions were in good agreement with the measured OH concentrations, with an observed-to-modeled ratio near one (0.70 ± 0.31) for isoprene mixing ratios between 1–2 ppb on average. The measured peroxy radical concentrations, reflecting the sum of HO2 and isoprene-based peroxy radicals, were generally lower than predicted by the box model in both years.
Griffith, S. M., Hansen, R. F., Dusanter, S., Stevens, P. S., Alaghmand, M., Bertman, S. B., Carroll, M. A., Erickson, M., Galloway, M., Grossberg, N., Hottle, J., Hou, J., Jobson, B. T., Kammrath, A., Keutsch, F. N., Lefer, B. L., Mielke, L. H., O'Brien, A., Shepson, P. B., Thurlow, M., Wallace, W., Zhang, N., and Zhou, X. L.: OH and HO2 radical chemistry during PROPHET 2008 and CABINEX 2009 – Part 1: Measurements and model comparison, Atmos. Chem. Phys., 13, 5403-5423, doi:10.5194/acp-13-5403-2013, 2013.