Improving Residential Wood Combustion Emissions Factors and Chemical Speciation with the Reactive Organic Carbon Framework

BENJAMIN MURPHY, Karl Seltzer, Amara Holder, Gabriel Isaacman-VanWertz, Havala Pye, United States Environmental Protection Agency

     Abstract Number: 708
     Working Group: Carbonaceous Aerosol

Abstract
Residential wood burning is one of the largest anthropogenic sources of organic carbon particles and vapors to the atmosphere in the United States, according to recent U.S. EPA National Emission Inventory estimates. The impact of these emissions on air quality is profound, especially in the wintertime when wood is used for heating, and it is expected to grow in relative importance in the future. Existing inventories and photochemical air quality models often use an outdated conceptual model of the phase partitioning of organic particulate and vapor mass. Specifically, regulatory test methods are used to quantify particulate matter emission factors from wood stoves with an operational definition of particulate matter (i.e., mass captured on a Teflon filter) that is susceptible to systematic biases corresponding to the temperature and dilution conditions of each individual test. Meanwhile, total hydrocarbons vapors are characterized using flame-ionization detection, which provides an uncertain measure of gas mixtures containing significant contribution from oxygenated molecules. Finally, the speciation of residential wood burning emissions needs to be revised with state-of-science understanding of key semivolatile and intermediate volatility compounds that are potent secondary organic aerosol precursors.

This presentation discusses the physical basis for and methodology we use to implement revisions to the PM and VOC emission factors and chemical speciation in U.S. EPA emissions modeling tools. Results quantify the impact these updates have on primary and secondary organic aerosol concentrations in the U.S. with the Community Multiscale Air Quality (CMAQ) model employing the new Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM). The new approach provides the most rigorous and complete translation to date of organic compound mass from residential wood burning emissions to air pollutant concentrations. Identification of key uncertainties including volatility distributions and OM:OC metrics point to critical areas for future research.

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