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Extending the Reactive Organic Carbon Framework to Understand Regulatory VOC and PM Emissions
Citation:
Murphy, B., K. Seltzer, H. Pye, E. D'Ambro, C. Heald, AND J. Kroll. Extending the Reactive Organic Carbon Framework to Understand Regulatory VOC and PM Emissions. AGU Fall Meeting, Virtual, LA, December 13 - 17, 2021.
Impact/Purpose:
This presentation will communicate to the research community how current test methods may be interpreted to better constrain the total organic carbon released from combustion emissions. Several long-standing barriers for communication between the regulatory and research communities are identified and explored. The presentation will offer to research a road-map for how to process and submit their data to EPA so that it may be appropriately be integrated into emissions modeling tools.
Description:
Organic emissions lead to ozone and particulate matter air pollution, which are known threats to both human and environmental health at global, regional, and local scales. Historically, the EPA has inventoried organic gas- and particle-phase emissions separately as VOC and PM-OC, respectively. However, the development of novel instrumentation and modeling capabilities has led to new terms and frameworks that often blur the line between gas- and particle-phase organics, which in turn have caused communication challenges between the regulatory and research-oriented air quality modeling communities. This is best highlighted by the inconsistent definition of “semivolatile.” The emissions testing community definition is based on species that actively partition in concentrated stack, plume or tailpipe conditions (~50-10,000 μg m-3), while the atmospheric science community definition is based on ambient conditions (0.1-10 μg m-3). Overall, two core challenges for air quality modeling that result from these communication challenges are the inclusion of semivolatile primary organic aerosol and the emission of intermediate volatility organic compounds, which are known to efficiently produce additional aerosol after atmospheric oxidation. Given the influence and impact of regulatory and research data products, it is vitally important to resolve inconsistencies and decrease the barrier of incorporating new science to inform policy modeling, uncertainty analysis, and source attribution. We propose unifying VOC, semivolatile and organic PM emissions modeling tools under the reactive organic carbon (ROC) framework to consider the enormous breadth of sources, properties, and impacts relevant for these critical classes of air pollutants. This presentation will demonstrate the limitations in conventional test methods for interpreting VOC and PM emissions, explain how these limitation are resolved with the ROC framework, share insights about potential emissions testing gaps that emerge using the ROC framework as a guide, and identify the specific modeling and data-reporting updates that should be made to fully realize the benefits of this comprehensive approach. Consideration is also given to future accommodations for emerging knowledge about important classes of compounds for environmental management like secondary organic aerosol precursors, organic fluorine compounds, etc.
