PhD Defense by Xiaoxi Liu

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  • Date/Time:
    • Thursday November 3, 2016
      12:00 pm - 3:00 pm
  • Location: ES&T 1229
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Summary Sentence: Measurements of Emissions from Agricultural Fires and Wildfires in the U.S.

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Measurements of Emissions from Agricultural Fires and Wildfires in the U.S.

Xiaoxi Liu


Directed by Dr. Greg Huey



Dr. L. Gregory Huey, Advisor
School of Earth and Atmospheric Sciences
Georgia Institute of Technology  Dr. Rodney Weber
School of Earth and Atmospheric Sciences
Georgia Institute of Technology

Dr. Yuhang Wang
School of Earth and Atmospheric Sciences
Georgia Institute of Technology  Dr. Robert Yokelson
Department of Chemistry
University of Montana

Dr. Nga Lee Ng
School of Chemical and Biochemical Engineering
Georgia Institute of Technology  

This work presents detailed airborne measurements of primary emissions from agricultural fires and wildfires in the U.S. and the chemical transformations of primary emissions in the agricultural fire plumes. Emissions from 15 agricultural fires in the southeastern U.S. were measured from the NASA DC-8 research aircraft during the summer 2013 Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS) campaign. A detailed set of emission factors (EFs) for 25 trace gases and 6 fine particle species was reported. Observed EFs are generally consistent with previous measurements of crop residue burning, but the fires studied here emitted high amounts of sulfur dioxide (SO2) and fine particles, especially primary organic aerosol (POA) and chloride. Filter-based measurements of aerosol light absorption implied that brown carbon (BrC) was ubiquitous in the plumes. With the calculated EFs, total annual SO2, nitrogen oxides (NOx) and carbon monoxide (CO) emissions from agricultural fires in Arkansas, Louisiana, Mississippi, and Missouri were estimated (within a factor of ~2) to be equivalent to ~2% SO2 from coal combustion and ~1% NOx and ~9% CO from mobile sources.
The chemical evolution of the primary emissions in 7 out of 15 agricultural plumes was examined in detail for ~1.2 hr. A Lagrangian plume cross-section model was used to simulate the evolution of ozone (O3), reactive nitrogen species, and organic aerosol (OA). In aged plumes, rapid production of O3, peroxyacetyl nitrate (PAN), and nitrate were observed with ΔO3/ΔCO, ΔPAN/ΔNOy, and Δnitrate/ΔNOy reaching ~0.1, ~0.3, and ~0.3. For 5 selected cases, the model reasonably simulated O3 formation but underestimated PAN formation. No significant evolution of OA mass or BrC absorption was observed. However, a consistent increase in oxygen-to-carbon (O/C) ratios of OA indicated that OA oxidation in the agricultural fire plumes was much faster than in urban and forest fire plumes.
Plumes from three wildfires in the western U.S. were measured from aircraft during SEAC4RS and the Biomass Burning Observation Project (BBOP). An extensive set of EFs for over 80 gases and 5 components of submicron particulate matter (PM1) from temperate wildfires were presented here. These include some rarely, or never before, measured oxygenated volatile organic compounds and multifunctional organic nitrates. The EFs from three wildfires are compared with those from previous airborne measurements of temperate wildfires, boreal forest fires, and temperate prescribed fires. These wildfires emitted high amounts of PM1 with an average EF that is over two times of prescribed fire EFs. The EFs were used to estimate the annual wildfire emissions of CO, NOx, total non-methane organic compound (NMOC), and PM1 from 11 western U.S. states. Whereas the estimated gas emissions are generally comparable with the 2011 National Emissions Inventory (NEI), our PM1 emission estimate (1530 ± 570 Gg yr-1) is over three times that of the NEI PM2.5 estimate mainly due to our high EF(PM1) and also higher than the PM2.5 emitted from all other sources in these states according to NEI. This supports the practice of prescribed burning that could reduce fine particle emissions

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  • Created By: Tatianna Richardson
  • Workflow Status: Published
  • Created On: Oct 18, 2016 - 9:11am
  • Last Updated: Oct 18, 2016 - 9:11am