Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-893
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
21 Oct 2016
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Regional background O3 and NOx in the Houston-Galveston- Brazoria (TX) region: A decadal-scale perspective
Loredana G. Suciu1, Robert J. Griffin2, and Caroline A. Masiello1 1Department of Earth Science, Rice University, Houston, 77005, USA
2Department of Civil and Environmental Engineering, Rice University, 5 Houston, 77005, USA
Abstract. Ozone (O3) in the lower troposphere is harmful to people and plants, particularly during summer, when photochemistry is the most active and higher temperatures favor local chemistry. Because of its dependence on the volatile organic compounds (VOCs) to nitrogen oxides (NOx) ratio, ground-level O3 is difficult to control locally, where many sources of these precursors contribute to its mixing ratio. In addition to local emissions, chemistry and transport, larger-scale factors also contribute to local O3 and NOx. These additional contributions (often referred to as "regional background") are not well quantified within the Houston-Galveston-Brazoria (HGB) region, impeding more efficient controls on precursor emissions to achieve compliance with the National Ambient Air Quality Standards for O3. In this study, we estimate regional background O3 and NOx in the HGB region and quantify their decadal-scale trends.

We use four different approaches based on principal component analysis (PCA) to quantify background O3 and NOx. Three of these approaches consist of independent PCA on both O3 and NOx for both 1-h and 8-h levels to compare our results with previous studies and to highlight the effect of both temporal and spatial scales. In the fourth approach, we co-varied O3, NOx and meteorology.

Our results show that the estimation of regional background O3 has less inherent uncertainty when it was constrained by NOx and meteorology, yielding a statistically significant temporal trend of −0.69 ± 0.27 ppb y−1. Likewise, the estimation of regional background NOx trend constrained by O3 and meteorology was −0.04 ± 0.02 ppb y−1. Our best estimates of 17-y average of season-scale background O3 and NOx were 46.72 ± 2.08 ppb and 6.80 ± 0.13 ppb, respectively.

Regional background O3 and NOx both have declined over time in the HGB region. This decline is likely caused by a combination of state of Texas controls on precursor emissions since 2007 and the increase in frequency of flow from the Gulf of Mexico over the same time period.


Citation: Suciu, L. G., Griffin, R. J., and Masiello, C. A.: Regional background O3 and NOx in the Houston-Galveston- Brazoria (TX) region: A decadal-scale perspective, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-893, in review, 2016.
Loredana G. Suciu et al.
Loredana G. Suciu et al.
Loredana G. Suciu et al.

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Short summary
Understanding of the variability of ozone (O3) in space and time is essential to the design of efficient air quality controls. We used statistical analysis of O3, nitrogen oxides (NOx) and weather measurements to estimate the large-scale contributions of O3 and NOx in southeastern Texas. We found that these "external" contributions have declined over time, likely due to a combination of controls on O3 precursors and increases in the frequency of prevailing southerly flow from the Gulf of Mexico.
Understanding of the variability of ozone (O3) in space and time is essential to the design of...
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