1Department of Chemistry, Indiana University, Bloomington, IN, USA
2Center for Research in Environmental Science, Indiana University, Bloomington, IN, USA
3School of Public and Environmental Affairs, Indiana University, Bloomington, IN, USA
4Mines Douai, CE, F59508, Douai, France
5Université Lille Nord de France, 59000, Lille, France
6Department of Chemistry, Western Michigan University, Kalamazoo, MI, USA
7Department of Chemistry, University of Michigan, Ann Arbor, MI, USA
8Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI, USA
9Department of Civil and Environmental Engineering, Washington State University, Pullman, WA, USA
10Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, USA
*now at: School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
Received: 31 May 2013 – Discussion started: 28 Jun 2013
Abstract. Total hydroxyl radical (OH) reactivity was measured at the PROPHET (Program for Research on Oxidants: PHotochemistry, Emissions, and Transport) forested field site in northern Michigan during the 2009 Community Atmosphere–Biosphere INteraction EXperiment (CABINEX). OH reactivity measurements were made with a turbulent-flow reactor instrument at three heights from the forest floor above (21 and 31 m) and below (6 m) the canopy at three different time periods during the CABINEX campaign. In addition to total OH reactivity measurements, collocated measurements of volatile organic compounds (VOCs), inorganic species, and ambient temperature were made at the different heights. These ancillary measurements were used to calculate the total OH reactivity, which was then compared to the measured values. Discrepancies between the measured and calculated OH reactivity, on the order of 1–24 s−1, were observed during the daytime above the canopy at the 21 and 31 m heights, as previously reported for this site. The measured OH reactivity below the canopy during the daytime was generally lower than that observed above the canopy. Closer analysis of the measurements of OH reactivity and trace gases suggests that the missing OH reactivity could come from oxidation products of VOCs. These results suggest that additional unmeasured trace gases, likely oxidation products, are needed to fully account for the OH reactivity measured during CABINEX.
Revised: 08 Jan 2014 – Accepted: 06 Feb 2014 – Published: 21 Mar 2014
Hansen, R. F., Griffith, S. M., Dusanter, S., Rickly, P. S., Stevens, P. S., Bertman, S. B., Carroll, M. A., Erickson, M. H., Flynn, J. H., Grossberg, N., Jobson, B. T., Lefer, B. L., and Wallace, H. W.: Measurements of total hydroxyl radical reactivity during CABINEX 2009 – Part 1: field measurements, Atmos. Chem. Phys., 14, 2923-2937, doi:10.5194/acp-14-2923-2014, 2014.