Atmospheric Measurement Techniques Discussions www.atmos-meas-tech-discuss.net 1867-8610 2 6 2009 10.5194/amtd-2-3055-2009 http://www.atmos-meas-tech-discuss.net/2/3055/2009/ http://www.atmos-meas-tech-discuss.net/2/3055/2009/amtd-2-3055-2009.html http://www.atmos-meas-tech-discuss.net/2/3055/2009/amtd-2-3055-2009.pdf 3055 3097 2009-12-04 Total peroxy nitrates (ΣPNs) in the atmosphere: the thermal dissociation-laser induced fluorescence (TD-LIF) technique and comparisons to speciated PAN measurements P. J. Wooldridge pjwool@berkeley.edu A. E. Perring T. H. Bertram F. M. Flocke J. M. Roberts H. B. Singh L. G. Huey J. A. Thornton J. G. Murphy J. L. Fry A. W. Rollins B. W. LaFranchi R. C. Cohen Department of Chemistry, University of California, Berkeley, CA, USA Department of Chemistry and Biochemistry, University of San Diego, La Jolla, CA, USA NCAR Atmospheric Chemistry Division, Boulder, CO, USA NOAA Earth System Research Laboratory, Boulder, CO, USA NASA Ames Research Center, Moffett Field, CA, USA School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA Department of Chemistry, University of Toronto, Toronto, Ontario, Canada Department of Chemistry, Reed College, Portland, OR, USA Department of Earth and Planetary Science, University of California, Berkeley, CA, USA 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 NO_x conditions. Interferences to the TD-LIF measurements are described along with strategies to minimize their effects. 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