10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Impact of Organic Aerosol Partitioning on U.S. Particle Emission Factors
BENJAMIN MURPHY, Christos Efstathiou, Havala Pye, United States Environmental Protection Agency
Abstract Number: 1519 Working Group: Carbonaceous Aerosol
Abstract Direct emissions of particulate-phase organic and inorganic compounds contribute the majority of near-field particle mass from combustion sources, especially in urban areas. For sources with substantial organic fractions (e.g. vehicles, fires, power plants, etc), previous studies have demonstrated the importance of considering reversible partitioning of organic compounds between the gas- and particulate-phases when linking laboratory/field measurements with predictions of ambient concentrations, from e.g. chemical transport models (see e.g. Murphy et al., 2017). For example, studies that characterize the emission factors or composition of particles from specific sources may be performed at much higher concentrations than what is relevant for the atmosphere and their emission factors must be adjusted to take nonlinear evaporation processes into account.
Any of several potential pitfalls could occur when combining emission factor databases (e.g. National Emissions Inventory, NEI), speciation databases (e.g. SPECIATE), emission models (e.g. MOVES, SMOKE) and chemical transport models (e.g. the Community Multiscale Air Quality model, CMAQ). These include how one corrects for adsorbed and absorbed vapors from the experiment, and how one applies distributions in volatility from literature in order to calculate the effects of partitioning on the pollutant phase distribution. Due to the complexity and enormity of these databases/models and the limited reporting from many of the studies that inform these systems, a comprehensive evaluation of these uncertainties is difficult.
We bridge the gaps between emissions inventories and models by reviewing the most important sources for direct organic particle emissions in the U.S. We then apply the updated emissions scale factors directly in CMAQ and assess their impact on policy analyses. Finally, we recommend revisions to the inventories and emissions models so that transport models best reproduce the emission magnitudes and trends that have been constrained by focused lab/field studies.
Murphy et al, ACP, https://doi.org/10.5194/acp-17-11107-2017, 2017.