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| Titel |
Observations of the temperature dependent response of ozone to NOx reductions in the Sacramento, CA urban plume |
| VerfasserIn |
B. W. LaFranchi, A. H. Goldstein, R. C. Cohen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 14 ; Nr. 11, no. 14 (2011-07-18), S.6945-6960 |
| Datensatznummer |
250009925
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| Publikation (Nr.) |
 copernicus.org/acp-11-6945-2011.pdf |
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| Zusammenfassung |
| Observations of NOx in the Sacramento, CA region show that mixing
ratios decreased by 30 % between 2001 and 2008. Here we use an
observation-based method to quantify net ozone (O3) production rates in the
outflow from the Sacramento metropolitan region and examine the O3
decrease resulting from reductions in NOx emissions. This observational
method does not rely on assumptions about detailed chemistry of ozone
production, rather it is an independent means to verify and test these
assumptions. We use an instantaneous steady-state model as well as a
detailed 1-D plume model to aid in interpretation of the ozone production
inferred from observations. In agreement with the models, the observations
show that early in the plume, the NOx dependence for Ox
(Ox = O3 + NO2) production is strongly coupled with temperature,
suggesting that temperature-dependent biogenic VOC emissions and other
temperature-related effects can drive Ox production between
NOx-limited and NOx-suppressed regimes. As a result, NOx
reductions were found to be most effective at higher temperatures over the 7
year period. We show that violations of the California 1-h O3
standard (90 ppb) in the region have been decreasing linearly with decreases
in NOx (at a given temperature) and predict that reductions of NOx
concentrations (and presumably emissions) by an additional 30 % (relative
to 2007 levels) will eliminate violations of the state 1 h standard in
the region. If current trends continue, a 30 % decrease in NOx is
expected by 2012, and an end to violations of the 1 h standard in the
Sacramento region appears to be imminent. |
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