Citation:

Murphy, B., K. Seltzer, H. Pye, E. D'Ambro, C. Heald, AND J. Kroll. Application of the Reactive Organic Carbon Framework to Modeling VOC and PM Emissions. 20th CMAS Conference, Virtual, North Carolina, November 01 - 05, 2021.

Impact/Purpose:

This presentation will cover efforts to update EPA emissions modeling workflows to consider the full range of SOA precursors and dynamic partitioning of primary emissions. This particular effort will summarize the inconsistencies between the emerging scientific knowledge and conventional EPA methods. Understanding these issues will impact the development of the next generation of emissions inventory and test method procedures.

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 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, data-reporting, and testing definition updates that should be made to fully realize the benefits of this comprehensive approach.

Record Details: