Comment on “Isotopic evidence for dominant secondary production of HONO in near-ground wildfire plumes.”
- Chemical Sciences Laboratory, NOAA/ESRL, Boulder, CO
Abstract. Chai et al. recently published measurements of wild fire (WF) derived oxides of nitrogen (NOx) and nitrous acid (HONO) and their isotopic composition. The method used to sample NOx, collection in alkaline solution, has a known 1:1 interference from another reactive nitrogen compound, acetyl peroxynitrate (PAN). Although PAN is thermally unstable, subsequent reactions with nitrogen dioxide (NO2) in effect extend the lifetime of PAN many times longer than the initial decomposition reaction would indicate. This, coupled with the rapid and efficient formation of PAN in WF plumes, means the NOx measurements reported by Chai et al. were severely impacted by PAN. In addition, the model reactions in the original paper did not include the reactions of NO2 with hydroxyl radical (OH) to form nitric acid, nor the efficient reaction of larger organic radicals with nitric oxide to form organic nitrates (RONO2).
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