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Project ID: 14-1-03-26

Year: 2014

Date Started: 06/01/2014

Date Completed: 09/12/2017

Title: Phase Dynamics of Wildland Fire Smoke Emissions and Their Secondary Organic Aerosols

Project Proposal Abstract: Although representing only a small mass fraction of the emissions from biomass burning, the emitted particle-phase organic species (organic aerosol, OA) exert importance influences on visibility, climate, and human health. Wildland fire, both prescribed and wildfires, is a potentially major source of atmospheric particulate matter across the US. Biomass burning emissions of OA are strongly dependent on fuel type and are also correlated with increased smoldering to flaming ratios. It is now understood that biomass burning emissions undergo further chemistry in the atmosphere, in both the gas and aqueous phases, leading to the formation of secondary organic aerosol (SOA). Biomass-burning derived SOA has potentially larger impacts, and on a broader scale, than do the direct (primary organic aerosol, POA) emissions, as recent work has shown that in some cases the SOA mass concentrations are several times those of the original POA. Three major difficulties presently exist in understanding the aerosol-related impacts from biomass burning. (1) Traditional methods that have measured emission factors for primary OA have not fully considered semivolatile OA species and the evolving amount of OA with dilution. The distribution of vapor pressures among the total emitted mass is needed to understand the evolving OA concentrations in a diluting plume and the vapor-phase mass concentrations available for oxidation and SOA formation. We have led a recent study that represents the first comprehensive measurement campaign aimed at quantifying the total potential aerosol emissions and their volatility distributions, both of which are needed to assess the mass concentrations that exist in the aerosol phase at any point in time and space. In addition, estimates of the aerosol size distribution are required for partitioning timescale assessments. (2) The precursor species to SOA formation are largely unknown, although recent work suggests that they include semivolatile species that may have evaporated from the particle phase in the diluting plume. (3) Recent work has shown that molecules with structures similar to those expected for biomass burning SOA precursors may be lost to the walls of traditional smog chambers, calling into question the SOA formation amounts observed in many laboratory studies and the application of these results to atmospheric models. We suggest that an improved knowledge of the phase partitioning behavior in smoke and its implications for measurements and modeling is a fundamental first step in improving estimates of biomass-burning-derived SOA. We propose a detailed study examining the phase partitioning behavior of biomass burning emissions under scenarios applicable to both the laboratory and the field. We will use (1) a model of aerosol size and volatility, (2) recently measured biomass-burning organic volatility distributions, and (3) recently observed organic vapor wall-loss rates to calculate the evolution of biomass-burning-derived gases and particles in laboratory studies and ambient plumes. Our objectives are: 1. Conduct detailed calculations of the phase partitioning behavior of fresh smoke emissions, including consideration of the evolving aerosol size distribution, with a view toward understanding conditions under which SOA precursors become available for oxidation; 2. Use the same framework to compute the potential phase partitioning behavior of oxidation products, to improve understanding of their potential impacts on PM2.5 concentrations; 3. Simulate and propose corrections for smog-chamber experiments where the sequestering of reactive species into chamber walls has not previously been explicitly considered. This proposed work represents the first comprehensive look at how the dynamics of plume dilution, under different ambient environment scenarios, affect the timescales and mechanisms of SOA precursor release and oxidation, a key uncertainty in modeling fire-derived SOA.

Principal Investigator: Sonia M. Kreidenweis

Agency/Organization: Colorado State University

Branch or Dept: Department of Atmospheric Science

Other Project Collaborators




Branch or Dept

Agreements Contact

Lisa M. Anaya Esquibel

Colorado State University

Sponsored Programs

Budget Contact

Lisa M. Anaya Esquibel

Colorado State University

Sponsored Programs

Co-Principal Investigator

Jeffrey R. Pierce

Colorado State University

Department of Atmospheric Science

Project Locations

Fire Science Exchange Network


Great Basin

Northern Rockies


Southern Rockies






Pacific Coast States








Project Deliverables

Final Report view or print

("Results presented in JFSP Final Reports may not have been peer-reviewed and should be interpreted as tentative until published in a peer-reviewed source.")

  ID Type Title
view or print go to website 3622 Journal Article Atmospheric Chemistry and Physics Discussions
  go to website 3768 Journal Article Atmospheric Chemistry and Physics
  go to website 3769 Journal Article Atmospheric Chemistry and Physics
view or print   7929 Final Report Summary Final Report Summary

Supporting Documents

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