On the role of monoterpene chemistry in the remote continental boundary layer
The formation of organic nitrates (RONO<sub>2</sub>) represents an important NO<sub>x</sub> (NO<sub>x</sub> = NO + NO<sub>2</sub>) sink in the remote and rural continental atmosphere, thus impacting ozone production and secondary organic aerosol (SOA)...
Main Authors: | , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2014-02-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | http://www.atmos-chem-phys.net/14/1225/2014/acp-14-1225-2014.pdf |
Summary: | The formation of organic nitrates (RONO<sub>2</sub>) represents an important
NO<sub>x</sub> (NO<sub>x</sub> = NO + NO<sub>2</sub>) sink in the remote and
rural continental atmosphere, thus impacting ozone production and secondary
organic aerosol (SOA) formation. In these remote and rural environments, the
organic nitrates are primarily derived from biogenic volatile organic
compounds (BVOCs) such as isoprene and monoterpenes. Although there are
numerous studies investigating the formation of SOA from monoterpenes, there
are few studies investigating monoterpene gas-phase chemistry. Using a
regional chemical transport model with an extended representation of organic
nitrate chemistry, we investigate the processes controlling the production and
fate of monoterpene nitrates (MTNs) over the boreal forest of Canada. MTNs
account for 5–12% of total oxidized nitrogen over the boreal forest, and
production via NO<sub>3</sub> chemistry is more important than production via OH
when the NO<sub>x</sub> mixing ratio is greater than 75 pptv. The regional
responses are investigated for two oxidation pathways of MTNs: one that
returns NO<sub>x</sub> to the atmosphere and one that converts MTNs into a
nitrate that behaves like HNO<sub>3</sub>. The likely situation is in between, and
these two assumptions bracket the uncertainty about this chemistry. In the
case where the MTNs return NO<sub>x</sub> after oxidation, their formation
represents a net chemical NO<sub>x</sub> loss that exceeds the net loss to
peroxy nitrate formation. When oxidation of MTNs produces a molecule that
behaves like HNO<sub>3</sub>, HNO<sub>3</sub> and MTNs are nearly equal chemical sinks
for NO<sub>x</sub>. This uncertainty in the oxidative fate of MTNs results in
changes in NO<sub>x</sub> of 8–14%, in O<sub>3</sub> of up to 3%, and in
OH of 3–6% between the two model simulations. |
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ISSN: | 1680-7316 1680-7324 |