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Project Number:
SHARP Data Analysis: Radical Budget and Ozone Production
Lead PI:
Barry Lefer
Institution(s) Represented:
University of Houston- Barry Lefer, Pennsylvania State University- William Brune, University of New Hampshire- Jack Dibb, University of Miami- Xinrong Ren, University of California at Los Angeles- Jochen Stutz
AQRP Project Manager:
Cynthia F. Murphy
TCEQ Project Liaison:
John Jolly
Awarded Amount:

Executive Summary- Project 10-032
SHARP Data Analysis: Radical Budget and Ozone Production
The chemistry of atmospheric radicals, especially the hydroxyl radical (OH) and hydroperoxyl radical (HO2), together called HOx, is deeply involved in the formation of secondary pollutants ozone and fine particles.  Radical precursors, such as nitrous acid (HONO) and formaldehyde (HCHO), significantly affect the HOx budget in urban environments such as Houston.  These chemical processes connect surface emissions, both human and natural, to local and regional pollution, and climate change.  This project will evaluate the radical budget and ozone production using the data collected during the Study of Houston Atmospheric Radical Precursors (SHARP) on the campus of the University of Houston in the spring of 2009.
The purpose of this work is to inform policy decisions related to the development of ozone control strategies for State Implementation Plans in Texas; particularly those that rely on the use of appropriately represented chemical reactions in photochemical modeling.  This project will directly support these goals by using statistical methods to analyze the observations related to ozone formation, and also using numeric zero-dimensional models with five different chemical mechanisms to simulate the oxidation processes during this study.  Using the model results, the radical budget will be calculated and the sensitivity of ozone production to oxides of nitrogen (NOx) and volatile organic compounds (VOCs) will be analyzed.  The model results also allow the comparison of the observed OH reactivity and ozone production rate to the model calculations.  The models used in this project have been previously used for similar studies (Shuang et al., 2010; Flynn et al., 2010; Bais et al., 2003, Wong and Stutz, 2010).
The primary objectives of this project include:
    • Identify the variation of measured HOx and HO2/OH with NOx and VOCs and compare to the model prediction.
    • Quantify OH reactivity and compare observed and calculated OH reactivity to examine any missing OH sink species.
    • Examine the significance of nighttime OH and determine the importance of both the reaction of O3 + alkenes and NO3 chemistry as nighttime OH sources.  
    • Compare and contrast the HOx levels in Houston to those in Mexico, Nashville and New York City.
    • Investigate the instantaneous O3 production and deviations of the NOx photostationary state due to clouds and aerosols.  This analysis will also include comparison of observed and calculated HO2 + RO2 mixing ratios and net O3 production.
    • Study the sensitivity of O3 production to NOx and VOCs.
    • Investigate the potential of HONO as a daytime precursor of OH.
    • Evaluate the role of nitryl chloride (ClNO2) as an early morning radical source and its' contribution to ozone production.
Investigate the processes creating strong correlations between HNO3 and gas phase chloride, and their implications for coupled Cl and NOx chemistry in Houston.

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Publications & Citations
Ren, X., D. van Duin, M. Cazorla, S. Chen, J. Mao, L. Zhan, W. H. Brune, J. H. Flynn, N. Grossberg, B. L. Lefer, B. Rappengluck, K. W. Wong. C. Tsai, J. Stutz, J. E. Dibb, B. T. Jobson, W. T. Luke and P. Kelley (2013), Atmospheric oxidation chemistry and ozone production: Results from SHARP 2009 in Houston, Texas, Journal of Geophysical Research-Atmospheres,118,5770-5780,doi:10.1002/jgrd.50342.