Influence of Highly Variable Spatial and Temporal VOC Emissions in Houston Texas on 1-hr and 8-hr Ozone SIP Modeling
This page updated March 4, 2009
Chair’s Air Pollution Seminar
Tuesday, March 24, 2009
Influence of Highly
Harvey Jeffries, Ph.D.
It is now clearly
understood that volatile organic compound (VOC) emissions events from
large petrochemical production and refining facilities along the
Houston Ship Channel have been the primary cause of very high 1-hr
mixing ratios observed at a surface monitoring stations in and around
More than $50 million in research, field programs, and modeling has been invested in this problem since 2000. New rules and regulatory monitoring have been implemented to address these problems and industries have invested in infrared cameras capable of detecting "events," unknown fugitive sources, and loading and shipping operational losses of highly volatile organics, all in an effort to mitigate the rapid ozone formation that often, but not always, occurs after such releases. Many parties believed that the shift from 1-hr to 8-hr ozone standard would ameliorate this problem and that future state implementation plan (SIP) focus would turn more to "background ozone."
My group's work at the University of North Carolina has instead shown that the current SIP modeling paradigm is basically incapable of effectively dealing with these phenomena. Analysis of observational data and multiple modeling episodes over three years and application of advanced pseudo-plume process analysis of 4-km and 1-km CAMx modeling episodes illustrate the complexity of representing these dominate features and reveal the extreme difficulty of using standard SIP modeling tools to support effective policies. This work also suggests that anywhere there is the potential for rapid ambient atmospheric VOC compositional change, there will be similar transient high ozone events created. The limited spatial and temporal character of this high ozone may result in its having a low frequency of detection by typical urban ozone monitoring networks.
A question to ponder is to what extent do the source behaviors and atmospheric processes identified in Houston occur in California communities with similar source categories?
Harvey Jeffries Ph.D., has been a Professor of
Atmospheric Chemistry in the Department of Environmental Sciences and
Engineering in the Gillings School of Global Public Health at the
University of North Carolina, Chapel Hill (UNC) since 1971. Dr.
Jeffries teaches graduate courses on atmospheric chemistry and
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