Nature 318, 347 - 349 (28 November 1985); doi:10.1038/318347a0

Relationship between peroxyacetyl nitrate and nitrogen oxides in the clean troposphere

H. B. Singh^*, L. J. Salas^*, B. A. Ridley^†, J. D. Shetter^†, N. M. Donahue^†, F. C. Fehsenfeld^‡§, D. W. Fahey^‡, D. D. Parrish^§, E. J. Williams^§, S. C. Liu^‡, G. Hübler^§ & P. C. Murphy^§

^*SRI International, Menlo Park, California 94025, USA
^†National Center for Atmospheric Research, Boulder, Colorado 80307, USA
^‡National Oceanic and Atmospheric Administration, Aeronomy Laboratory, Boulder, Colorado 80303, USA
^§Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, USA
Present addresses: NASA Ames Research Center, Moffett Field, California 94035, USA (H.B.S. and L.J.S.).

Nitrogen oxides have a key role in the chemistry of the polluted and the unpolluted atmosphere¹⁻⁴. It has been proposed that important quantities of nitrogen oxides may be contained in the form of peroxyacetyl nitrate (PAN) especially in the colder regions of the middle and upper troposphere^5,6. Surface and aircraft observations of PAN have confirmed its ubiquity in the remote troposphere where it has been measured at mixing ratios of 10−500 p.p.t.v. (parts per 10¹² v/v) (refs 7,8). To date, no study that is representative of the remote atmosphere has been made to assess directly the concentrations of PAN compared with that of the inorganic nitrogen oxides (NO and NO₂). Here we present the first study in which the mixing ratios of PAN, and nitrogen oxides—as wellas those of peroxypropionyl nitrate (PPN) and O₃ and relevant meteorological parameters—were measured concurrently at a location that receives clean, continental air. The results show that in clean conditions nitrogen oxides present in the form of PAN can be as much or more abundant than the inorganic form.

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