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Title: Formation and evolution of Tar Balls from Northwestern US wildfires

Biomass burning is a major source of light-absorbing black and brown carbonaceous particles. Brown carbon is a poorly characterized mixture that includes tar balls (TBs), a type of carbonaceous particle apparently unique to biomass burning. Here we describe the first atmospheric observations of the formation and evolution of TBs from forest fires. Aerosol particles were collected on TEM grids during aircraft transects at various downwind distances from the Colockum Tarp wildland fire. TB mass fractions, derived from TEM and in-situ measurements, increased from < 1 % near the fire to 31–45 % downwind, with little change in TB diameter. Single-scattering albedo determined from scattering and absorption measurements increased slightly with downwind distance. Similar TEM and SSA results were observed sampling multiple wildfires. Mie calculations are consistent with weak light absorbance by TBs (m = 1.56–0.02i) but not consistent with order-of-magnitude stronger absorption observed in different settings. The field-derived TB mass fractions reported here indicate that this particle type should be accounted for in biomass-burn emission inventories.
ORCiD logo [1] ;  [2] ;  [3] ; ORCiD logo [4] ;  [1] ;  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States). Environmental and Climate Sciences
  2. Arizona State Univ., Tempe, AZ (United States). School of Earth and Space Exploration and School of Molecular Sciences
  3. Meteorological Research Inst. (Japan). Atmospheric Environment and Applied Meteorology Research Dept.
  4. Aerodyne Research Inc., Billerica, MA (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 1680-7375
Grant/Contract Number:
SC0012704; 2-1703; 2-1403; JP25740008; JP16K16188; 205689; SC0014287
Accepted Manuscript
Journal Name:
Atmospheric Chemistry and Physics Discussions (Online)
Additional Journal Information:
Journal Name: Atmospheric Chemistry and Physics Discussions (Online); Journal Volume: 2018; Journal ID: ISSN 1680-7375
European Geosciences Union
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23). Climate and Environmental Sciences Division; Global Environment Research Fund (Japan); Japan Society for the Promotion of Science (JSPS)
Country of Publication:
United States
OSTI Identifier: