Oxygenated Interface on Biomass Burn Tar Balls Determined bySingle Particle Scanning Transmission X-ray Microscopy

Journal Article · Thu Jun 21 04:00:00 EDT 2007 · Journal of Physical Chemistry A

DOI:https://doi.org/10.1021/jp070155u· OSTI ID:928719

Tivanski, A V; Hopkins, R J; Tyliszczak, T; Gilles, M K

Carbonaceous particles originating from biomass burning canaccount for a large fraction of organic aerosols in a local environment.Presently, their composition, physical and chemical properties, as wellas their environmental effects are largely unknown. Tar balls, a distincttype of highly spherical carbonaceous biomass burn particles, have beenobserved in a number of field campaigns. The Yosemite AerosolCharacterization Study that took place in summer 2002 occurred during anactive fire season in the western United States; tar balls collectedduring this field campaign are described in this article. Scanningtransmission X-ray microscopy and near-edge X-ray absorption finestructure spectroscopy are used to determine the shape, structure, andsize-dependent chemical composition of ~;150 individual sphericalparticles ranging in size from 0.15 to 1.2mu m.The elemental compositionof tar balls is ~;55 percent atomic carbon and ~;45 percent atomicoxygen. Oxygen is present primarily as carboxylic carbonyls andoxygen-substituted alkyl (O-alkyl-C) functional groups, followed bymoderate amounts of ketonic carbonyls. The observed chemical composition,density, and carbon functional groups are distinctly different from sootor black carbon and more closely resemble high molecular weight polymerichumic-like substances, which could account for their reported opticalproperties. A detailed examination of the carboxylic carbonyl andO-alkyl-C functional groups as a function of particle size reveals a thinoxygenated interface layer. The high oxygen content, as well as thepresence of water-soluble carboxylic carbonyl groups, could account forthe reported hygroscopic properties of tar balls. The presence of theoxygenated layer is attributed to atmospheric processing of biomass burnparticles.

• Research Organization: Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
• Sponsoring Organization: USDOE Director. Office of Science. Biological andEnvironmental ResearchAtmospheric Sciences Program
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 928719
• Report Number(s): LBNL--62120; BnR: KP1205030
• Journal Information: Journal of Physical Chemistry A, Journal Name: Journal of Physical Chemistry A Journal Issue: 25 Vol. 111
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
BIOMASS
CARBON
CARBONYLS
CHEMICAL COMPOSITION
CHEMICAL PROPERTIES
ENVIRONMENTAL EFFECTS
FINE STRUCTURE
MICROSCOPY
MOLECULAR WEIGHT
OPTICAL PROPERTIES
OXYGEN
PARTICLE SIZE
SPECTROSCOPY
TAR