Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City
The emission characteristics of mobile sources in the Mexico City Metropolitan Area (MCMA) have changed significantly over the past few decades in response to emission control policies, advancements in vehicle technologies and improvements in fuel quality, among others. Along with these changes, con...
| Main Authors: | , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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Copernicus Publications on behalf of the European Geosciences Union
2011
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| Online Access: | http://hdl.handle.net/1721.1/64762 https://orcid.org/0000-0002-3596-5334 https://orcid.org/0000-0003-2339-3225 |
| _version_ | 1826195234002829312 |
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| author | Molina, Mario J. Lei, Wenfang Molina, Luisa Tan Zavala-Perez, Miguel Angel |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Molina, Mario J. Lei, Wenfang Molina, Luisa Tan Zavala-Perez, Miguel Angel |
| author_sort | Molina, Mario J. |
| collection | MIT |
| description | The emission characteristics of mobile sources in the Mexico City Metropolitan Area (MCMA) have changed significantly over the past few decades in response to emission control policies, advancements in vehicle technologies and improvements in fuel quality, among others. Along with these changes, concurrent non-linear changes in photochemical levels and criteria pollutants have been observed, providing a unique opportunity to understand the effects of perturbations of mobile emission levels on the photochemistry in the region using observational and modeling approaches. The observed historical trends of ozone (O3), carbon monoxide (CO) and nitrogen oxides (NOx) suggest that ozone production in the MCMA has changed from a low to a high VOC-sensitive regime over a period of 20 years. Comparison of the historical emission trends of CO, NOx and hydrocarbons derived from mobile-source emission studies in the MCMA from 1991 to 2006 with the trends of the concentrations of CO, NOx, and the CO/NOx ratio during peak traffic hours also indicates that fuel-based fleet average emission factors have significantly decreased for CO and VOCs during this period whereas NOx emission factors do not show any strong trend, effectively reducing the ambient VOC/NOx ratio. This study presents the results of model analyses on the sensitivity of the observed ozone levels to the estimated historical changes in its precursors. The model sensitivity analyses used a well-validated base case simulation of a high pollution episode in the MCMA with the mathematical Decoupled Direct Method (DDM) and the standard Brute Force Method (BFM) in the 3-D CAMx chemical transport model. The model reproduces adequately the observed historical trends and current photochemical levels. Comparison of the BFM and the DDM sensitivity techniques indicates that the model yields ozone values that increase linearly with NOx emission reductions and decrease linearly with VOC emission reductions only up to 30% from the base case. We further performed emissions perturbations from the gasoline fleet, diesel fleet, all mobile (gasoline plus diesel) and all emission sources (anthropogenic plus biogenic). The results suggest that although large ozone reductions obtained in the past were from changes in emissions from gasoline vehicles, currently significant benefits could be achieved with additional emission control policies directed to regulation of VOC emissions from diesel and area sources that are high emitters of alkenes, aromatics and aldehydes. |
| first_indexed | 2024-09-23T10:09:30Z |
| format | Article |
| id | mit-1721.1/64762 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T10:09:30Z |
| publishDate | 2011 |
| publisher | Copernicus Publications on behalf of the European Geosciences Union |
| record_format | dspace |
| spelling | mit-1721.1/647622024-05-15T08:44:14Z Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City Molina, Mario J. Lei, Wenfang Molina, Luisa Tan Zavala-Perez, Miguel Angel Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Molina, Luisa Tan Molina, Luisa Tan Zavala, M. Molina, Mario J. Lei, Wenfang The emission characteristics of mobile sources in the Mexico City Metropolitan Area (MCMA) have changed significantly over the past few decades in response to emission control policies, advancements in vehicle technologies and improvements in fuel quality, among others. Along with these changes, concurrent non-linear changes in photochemical levels and criteria pollutants have been observed, providing a unique opportunity to understand the effects of perturbations of mobile emission levels on the photochemistry in the region using observational and modeling approaches. The observed historical trends of ozone (O3), carbon monoxide (CO) and nitrogen oxides (NOx) suggest that ozone production in the MCMA has changed from a low to a high VOC-sensitive regime over a period of 20 years. Comparison of the historical emission trends of CO, NOx and hydrocarbons derived from mobile-source emission studies in the MCMA from 1991 to 2006 with the trends of the concentrations of CO, NOx, and the CO/NOx ratio during peak traffic hours also indicates that fuel-based fleet average emission factors have significantly decreased for CO and VOCs during this period whereas NOx emission factors do not show any strong trend, effectively reducing the ambient VOC/NOx ratio. This study presents the results of model analyses on the sensitivity of the observed ozone levels to the estimated historical changes in its precursors. The model sensitivity analyses used a well-validated base case simulation of a high pollution episode in the MCMA with the mathematical Decoupled Direct Method (DDM) and the standard Brute Force Method (BFM) in the 3-D CAMx chemical transport model. The model reproduces adequately the observed historical trends and current photochemical levels. Comparison of the BFM and the DDM sensitivity techniques indicates that the model yields ozone values that increase linearly with NOx emission reductions and decrease linearly with VOC emission reductions only up to 30% from the base case. We further performed emissions perturbations from the gasoline fleet, diesel fleet, all mobile (gasoline plus diesel) and all emission sources (anthropogenic plus biogenic). The results suggest that although large ozone reductions obtained in the past were from changes in emissions from gasoline vehicles, currently significant benefits could be achieved with additional emission control policies directed to regulation of VOC emissions from diesel and area sources that are high emitters of alkenes, aromatics and aldehydes. National Science Foundation (U.S.) (ATM-0528227) Mexico. Comisión Ambiental Metropolitana 2011-07-07T16:02:57Z 2011-07-07T16:02:57Z 2009-01 2008-11 Article http://purl.org/eprint/type/JournalArticle 1680-7324 1680-7316 http://hdl.handle.net/1721.1/64762 Zavala, M., Lei, W., Molina, M. J., and Molina, L. T.: Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City, Atmos. Chem. Phys., 9, 39-55. https://orcid.org/0000-0002-3596-5334 https://orcid.org/0000-0003-2339-3225 en_US http://dx.doi.org/10.5194/acp-9-39-2009 Atmospheric Chemistry and Physics Creative Commons Attribution 3.0 http://creativecommons.org/licenses/by/3.0 application/pdf Copernicus Publications on behalf of the European Geosciences Union Copernicus |
| spellingShingle | Molina, Mario J. Lei, Wenfang Molina, Luisa Tan Zavala-Perez, Miguel Angel Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City |
| title | Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City |
| title_full | Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City |
| title_fullStr | Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City |
| title_full_unstemmed | Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City |
| title_short | Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City |
| title_sort | modeled and observed ozone sensitivity to mobile source emissions in mexico city |
| url | http://hdl.handle.net/1721.1/64762 https://orcid.org/0000-0002-3596-5334 https://orcid.org/0000-0003-2339-3225 |
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