Global Budget and Distribution of Peroxyacetyl Nitrate (PAN) for Present and Preindustrial Scenarios

Anwar Khan, Michael C Cooke, Steven R Utembe, Alewx T Archibald, R.G. Derwent, M.E. Jenkin, K.E. Leather, C.J. Percival, Dudley Shallcross

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Abstract

A global 3-D chemistry and transport model, STOCHEM integrated with a detailed VOC oxidation scheme (CRI v2-R5) has been employed to study the important NOx reservoir compound, peroxyacetyl nitrate (PAN). Globally, PAN is produced entirely by the reaction of acetyl peroxy radicals (CH3CO3)
with NO2 and up to 2.0 ppb of PAN is found over the polluted regions of North America during June-July-August for the present scenario. The imbalances between model and measurement data are noted, with STOCHEM-CRI overestimating PAN mixing ratios relative to the measurement data by +17 and
+80 pptv for the lower and upper troposphere, respectively. The inclusion of additional HOx recycling mechanisms (e.g. related to isoprene oxidation) in STOCHEM-CRI causes a decrease in PAN in a present scenario by as much as 40% over sink regions and reduces the model-measurement disagreement by 90% for the lower troposphere and 40% for the upper troposphere. The lower NOx emissions and CH3CO3 formation upon including HOx recycling in a preindustrial scenario led to a decrease in PAN formation by as much as 40%. The decrease in PAN formation results in less nitrogen being transported to remote regions which in turn leads to the greatest percentage change in O3 concentration (9% decrease) in the equatorial regions.
Original languageEnglish
Article number130
Number of pages10
JournalInternational Journal of Earth & Environmental Sciences
Volume2
Issue number1
DOIs
Publication statusPublished - 3 Mar 2017

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