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Ozone Reactivity of Air Pollutant Emission Inventories. Zachariah Adelman University of North Carolina William Carter University of California at Riverside Gail Tonnesen US EPA. 3-State Air Quality Study (3SAQS). Colorado Utah Wyoming
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Ozone Reactivity of Air Pollutant Emission Inventories Zachariah Adelman University of North Carolina William Carter University of California at Riverside Gail Tonnesen US EPA 12th Annual CMAS Conference October 28-30, 2013
3-State Air Quality Study (3SAQS) • Colorado Utah Wyoming • Cooperative agreement between UNC and National Park Service • Broad modeling and data warehousing project to support oil and gas NEPA modeling 12th Annual CMAS Conference October 28-30, 2013
VOC Reactivity • Volatile organic compounds (VOCs) react at different rates and via different mechanisms to form ozone • Reactivity: change in ozone with change in VOC emissions • f(Chemistry): reaction rate and mechanism • f(Ambient conditions): physical and chemical • f(Emissions change): magnitude and sign 12th Annual CMAS Conference October 28-30, 2013
VOC Reactivity • Reactivity may be calculated from chamber experiments or photochemical modeling • Incremental reactivity: dO3/dVOC • Greatest under high NOx conditions • Max Incremental Reactivity (MIR) – NOx conditions that yield highest VOC reactivity • Max Ozone Incremental Reactivity (MOIR) - NOx conditions that yield highest peak [O3] 12th Annual CMAS Conference October 28-30, 2013
Reactivity Applications • Conventional • Development of O3 mitigation strategies that replace high with low reactive VOCs • Photochemical grid modeling calculations of lumped VOC reactivity • This work • Reactivity-based perspective of emissions inventories 12th Annual CMAS Conference October 28-30, 2013
VOC Chemical Speciation • Speciation profiles: chemical composition of emission sources • Derived from source testing and lab studies • Mass fractions of organic compounds • Convert inventory VOC to photochemical mechanism species • SPECIATE database • 1000+ emission source profiles 12th Annual CMAS Conference October 28-30, 2013
VOC Emissions Reactivity • Profile Total MIR • Profile 7: Natural Gas Turbine • 70% methane, MIRCH4 = 0.014 gO3/gCH4 • 30% formaldehyde, MIRFORM = 9.46 gO3/gH2CO • Total MIR = 0.7MIRCH4 + 0.3MIRFORM = 2.85 gO3/gVOC • SPECIATE database reactivity now completed • Carter estimated MIR, MOIR, EBIR, for all 1700+ compounds in the database, including complex mixtures 12th Annual CMAS Conference October 28-30, 2013
VOC Emissions Reactivity RTOG = TOG * Profile Total MIR RTOG/TOG = Relative emission reactivity 12th Annual CMAS Conference October 28-30, 2013
VOC Emissions Reactivity RTOG = TOG * Profile Total MIR RTOG/TOG = Relative emission reactivity 12th Annual CMAS Conference October 28-30, 2013
Conclusions • Reactivity-based analysis of inventories focuses on sources with greatest ozone formation potential • The validity of the analysis is dependent on the quality of emissions speciation data • Reactivity metrics are based on “typical” urban conditions: extensibility problem 12th Annual CMAS Conference October 28-30, 2013
Future Work • Use RTOG results to explore inventory and speciation trends • Look at the results from alternative reactivity metrics (MOIR and EBIR) • Can this same concept be applied to VOC toxicity or other health effects endpoints? 12th Annual CMAS Conference October 28-30, 2013
Acknowledgements 3SAQS Team 3SAQS Cooperators National Park Service National Forest Service Bureau of Land Management States of CO, UT, WY EPA Region 8 • UNC • WRAP • ENVIRON • Colorado State University • UC Riverside 12th Annual CMAS Conference October 28-30, 2013