Atmos. Chem. Phys. Discuss., 13, 19085-19120, 2013
www.atmos-chem-phys-discuss.net/13/19085/2013/
doi:10.5194/acpd-13-19085-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Slower ozone production in Houston, Texas following emission reductions: evidence from Texas Air Quality Studies in 2000 and 2006
W. Zhou1, D. S. Cohan1, and B. H. Henderson2
1Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA
2Environmental Engineering Sciences, University of Florida, Gainesville, FL 32611, USA

Abstract. Airborne measurements from two Texas Air Quality Study (TexAQS) field campaigns have been used to investigate changes of ozone production in Houston, Texas, from 2000 to 2006, a period of major emission reduction measures at petrochemical and other sources. Simultaneous declines in nitrogen oxides (NOx=NO+NO2) and highly reactive volatile organic compounds (HRVOCs) were observed between the two periods. We simulated HOx (OH and HO2) and organic radicals with a box model, the Dynamically Simple Model of Atmospheric Chemical Complexity, constrained by available airborne observations. Parameters such as total radical production, total OH reactivity of VOCs and ozone production rate (P(O3) are computed to characterize the change of ozone production between 2000 and 2006 in the Houston area. The reduction in HRVOCs led to a decline in total radical production by 20–50%. Ozone production rates in the Houston area declined by 40–50% from 2000 to 2006, to which the reduction in NOx and HRVOCs had large contributions. Despite the significant decline in P(O3), ozone production efficiency held steady, and VOC-sensitive conditions dominated during times of most rapid ozone formation. Our results highlight the importance of ongoing HRVOC controls to further reduce O3 levels in the Houston area.

Citation: Zhou, W., Cohan, D. S., and Henderson, B. H.: Slower ozone production in Houston, Texas following emission reductions: evidence from Texas Air Quality Studies in 2000 and 2006, Atmos. Chem. Phys. Discuss., 13, 19085-19120, doi:10.5194/acpd-13-19085-2013, 2013.
 
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