Insights into hydroxyl measurements and atmospheric oxidation in a California forest J. Mao1,2, X. Ren3, L. Zhang4, D. M. Van Duin4, R. C. Cohen5, J.-H. Park6, A. H. Goldstein6, F. Paulot7,*, M. R. Beaver7,**, J. D. Crounse7, P. O. Wennberg7, J. P. DiGangi8,***, S. B. Henry8, F. N. Keutsch8, C. Park9,****, G. W. Schade9, G. M. Wolfe10,*****, J. A. Thornton10, and W. H. Brune4 1Program in Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ, USA 2Geophysical Fluid Dynamics Laboratory, NOAA, Princeton, NJ, USA 3Air Resources Laboratory, NOAA, Silver Spring, MD, USA 4Department of Meteorology, Pennsylvania State University, University Park, PA, USA 5Department of Chemistry and Department of Earth and Planetary Science, University of California Berkeley, Berkeley, CA, USA 6Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, CA, USA 7Environmental Science and Engineering, California Institute of Technology, Pasadena, CA, USA 8Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA 9Department of Atmospheric Sciences, Texas A&M University, College Station, TX, USA 10Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA *now at: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA **now at: National Exposure Research Laboratory, Environmental Protection Agency, Research Triangle Park, NC, USA ***now at: Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, USA ****now at: Department of Atmospheric Environmental Sciences, Pusan National University, South Korea *****now at: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
Abstract. The understanding of oxidation in forest atmospheres is being challenged by
measurements of unexpectedly large amounts of hydroxyl (OH). A significant
number of these OH measurements were made by laser-induced fluorescence in
low-pressure detection chambers (called Fluorescence Assay with Gas
Expansion (FAGE)) using the Penn State Ground-based Tropospheric Hydrogen
Oxides Sensor (GTHOS). We deployed a new chemical removal method to measure
OH in parallel with the traditional FAGE method in a California forest. The
new method gives on average only 40–60% of the OH from the traditional
method and this discrepancy is temperature dependent. Evidence indicates
that the new method measures atmospheric OH while the traditional method is
affected by internally generated OH, possibly from oxidation of biogenic
volatile organic compounds. The improved agreement between OH measured by
this new technique and modeled OH suggests that oxidation chemistry in at
least one forest atmosphere is better understood than previously thought.
Citation: Mao, J., Ren, X., Zhang, L., Van Duin, D. M., Cohen, R. C., Park, J.-H., Goldstein, A. H., Paulot, F., Beaver, M. R., Crounse, J. D., Wennberg, P. O., DiGangi, J. P., Henry, S. B., Keutsch, F. N., Park, C., Schade, G. W., Wolfe, G. M., Thornton, J. A., and Brune, W. H.: Insights into hydroxyl measurements and atmospheric oxidation in a California forest, Atmos. Chem. Phys., 12, 8009-8020, doi:10.5194/acp-12-8009-2012, 2012.