Observations of the temperature dependent response of ozone to NO<sub>x</sub> reductions in the Sacramento, CA urban plume
Observations of NO<sub>x</sub> 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 (O<sub>3</sub>) production rates in the outflow from the Sacramento metropolitan region a...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2011-07-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/11/6945/2011/acp-11-6945-2011.pdf |
| _version_ | 1818838544686252032 |
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| author | R. C. Cohen A. H. Goldstein B. W. LaFranchi |
| author_facet | R. C. Cohen A. H. Goldstein B. W. LaFranchi |
| author_sort | R. C. Cohen |
| collection | DOAJ |
| description | Observations of NO<sub>x</sub> 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 (O<sub>3</sub>) production rates in the outflow from the Sacramento metropolitan region and examine the O<sub>3</sub> decrease resulting from reductions in NO<sub>x</sub> 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 NO<sub>x</sub> dependence for O<sub>x</sub> (O<sub>x</sub> = O<sub>3</sub> + NO<sub>2</sub>) production is strongly coupled with temperature, suggesting that temperature-dependent biogenic VOC emissions and other temperature-related effects can drive O<sub>x</sub> production between NO<sub>x</sub>-limited and NO<sub>x</sub>-suppressed regimes. As a result, NO<sub>x</sub> reductions were found to be most effective at higher temperatures over the 7 year period. We show that violations of the California 1-h O<sub>3</sub> standard (90 ppb) in the region have been decreasing linearly with decreases in NO<sub>x</sub> (at a given temperature) and predict that reductions of NO<sub>x</sub> 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 NO<sub>x</sub> is expected by 2012, and an end to violations of the 1 h standard in the Sacramento region appears to be imminent. |
| first_indexed | 2024-12-19T03:40:05Z |
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| id | doaj.art-df1273aedb4647ab914a416980c9f82a |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-19T03:40:05Z |
| publishDate | 2011-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-df1273aedb4647ab914a416980c9f82a2022-12-21T20:37:16ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242011-07-0111146945696010.5194/acp-11-6945-2011Observations of the temperature dependent response of ozone to NO<sub>x</sub> reductions in the Sacramento, CA urban plumeR. C. CohenA. H. GoldsteinB. W. LaFranchiObservations of NO<sub>x</sub> 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 (O<sub>3</sub>) production rates in the outflow from the Sacramento metropolitan region and examine the O<sub>3</sub> decrease resulting from reductions in NO<sub>x</sub> 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 NO<sub>x</sub> dependence for O<sub>x</sub> (O<sub>x</sub> = O<sub>3</sub> + NO<sub>2</sub>) production is strongly coupled with temperature, suggesting that temperature-dependent biogenic VOC emissions and other temperature-related effects can drive O<sub>x</sub> production between NO<sub>x</sub>-limited and NO<sub>x</sub>-suppressed regimes. As a result, NO<sub>x</sub> reductions were found to be most effective at higher temperatures over the 7 year period. We show that violations of the California 1-h O<sub>3</sub> standard (90 ppb) in the region have been decreasing linearly with decreases in NO<sub>x</sub> (at a given temperature) and predict that reductions of NO<sub>x</sub> 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 NO<sub>x</sub> is expected by 2012, and an end to violations of the 1 h standard in the Sacramento region appears to be imminent.http://www.atmos-chem-phys.net/11/6945/2011/acp-11-6945-2011.pdf |
| spellingShingle | R. C. Cohen A. H. Goldstein B. W. LaFranchi Observations of the temperature dependent response of ozone to NO<sub>x</sub> reductions in the Sacramento, CA urban plume Atmospheric Chemistry and Physics |
| title | Observations of the temperature dependent response of ozone to NO<sub>x</sub> reductions in the Sacramento, CA urban plume |
| title_full | Observations of the temperature dependent response of ozone to NO<sub>x</sub> reductions in the Sacramento, CA urban plume |
| title_fullStr | Observations of the temperature dependent response of ozone to NO<sub>x</sub> reductions in the Sacramento, CA urban plume |
| title_full_unstemmed | Observations of the temperature dependent response of ozone to NO<sub>x</sub> reductions in the Sacramento, CA urban plume |
| title_short | Observations of the temperature dependent response of ozone to NO<sub>x</sub> reductions in the Sacramento, CA urban plume |
| title_sort | observations of the temperature dependent response of ozone to no sub x sub reductions in the sacramento ca urban plume |
| url | http://www.atmos-chem-phys.net/11/6945/2011/acp-11-6945-2011.pdf |
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