Abundance of no3 derived organo-nitrates and their importance in the atmosphere
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Date
2021Author
Foulds, Amy
Khan, M. Anwar H.
Shallcross, Dudley E.
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The chemistry of the nitrate radical and its contribution to organo-nitrate formation in
the troposphere has been investigated using a mesoscale 3-D chemistry and transport model, WRFChem-CRI. The model-measurement comparisons of NO2
, ozone and night-time N2O5 mixing
ratios show good agreement supporting the model’s ability to represent nitrate (NO3
) chemistry
reasonably. Thirty-nine organo-nitrates in the model are formed exclusively either from the reaction
of RO2 with NO or by the reaction of NO3 with alkenes. Temporal analysis highlighted a significant
contribution of NO3
-derived organo-nitrates, even during daylight hours. Night-time NO3
-derived
organo-nitrates were found to be 3-fold higher than that in the daytime. The reactivity of daytime
NO3 could be more competitive than previously thought, with losses due to reaction with VOCs
(and subsequent organo-nitrate formation) likely to be just as important as photolysis. This has
highlighted the significance of NO3
in daytime organo-nitrate formation, with potential implications
for air quality, climate and human health. Estimated atmospheric lifetimes of organo-nitrates showed
that the organo-nitrates act as NOx reservoirs, with particularly short-lived species impacting on air
quality as contributors to downwind ozone formation.