Articles | Volume 3, issue 3
Atmos. Meas. Tech., 3, 593–607, 2010
Atmos. Meas. Tech., 3, 593–607, 2010

  12 May 2010

12 May 2010

Total Peroxy Nitrates (ΣPNs) in the atmosphere: the Thermal Dissociation-Laser Induced Fluorescence (TD-LIF) technique and comparisons to speciated PAN measurements

P. J. Wooldridge1, A. E. Perring1, T. H. Bertram2, F. M. Flocke3, J. M. Roberts4, H. B. Singh5, L. G. Huey6, J. A. Thornton7, G. M. Wolfe7, J. G. Murphy8, J. L. Fry9, A. W. Rollins1, B. W. LaFranchi1, and R. C. Cohen1,10 P. J. Wooldridge et al.
  • 1Department of Chemistry, University of California, Berkeley, CA, USA
  • 2Department of Chemistry and Biochemistry, University of San Diego, La Jolla, CA, USA
  • 3NCAR Atmospheric Chemistry Division, Boulder, CO, USA
  • 4NOAA Earth System Research Laboratory, Boulder, CO, USA
  • 5NASA Ames Research Center, Moffett Field, CA, USA
  • 6School of Earth & Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
  • 7Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA
  • 8Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
  • 9Department of Chemistry, Reed College, Portland, OR, USA
  • 10Department of Earth and Planetary Science, University of California, Berkeley, CA, USA

Abstract. Peroxyacetyl nitrate (PAN) and its chemical analogues are increasingly being quantified in the ambient atmosphere by thermal dissociation (TD) followed by detection of either the peroxyacyl radical or the NO2 product. Here we present details of the technique developed at University of California, Berkeley which detects the sum of all peroxynitrates (ΣPNs) via laser-induced fluorescence (LIF) of the NO2 product. We review the various deployments and compare the Berkeley ΣPNs measurements with the sums of PAN and its homologue species detected individually by other instruments. The observed TD-LIF ΣPNs usually agree to within 10% with the summed individual species, thus arguing against the presence of significant concentrations of unmeasured PAN-type compounds in the atmosphere, as suggested by some photochemical mechanisms. Examples of poorer agreement are attributed to a sampling inlet design that is shown to be inappropriate for high NOx conditions. Interferences to the TD-LIF measurements are described along with strategies to minimize their effects.