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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, D06213, doi:10.1029/2003JD004169, 2004

Atmospheric tar balls: Particles from biomass and biofuel burning

Mihály Pósfai

Department of Earth and Environmental Sciences, University of Veszprém, Veszprém, Hungary


András Gelencsér

Air Chemistry Group, Hungarian Academy of Sciences, Veszprém, Hungary


Renáta Simonics

Department of Earth and Environmental Sciences, University of Veszprém, Veszprém, Hungary


Krisztina Arató

Department of Earth and Environmental Sciences, University of Veszprém, Veszprém, Hungary


Jia Li

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, USA


Peter V. Hobbs

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA


Peter R. Buseck

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, USA
Department of Geological Sciences, Arizona State University, Tempe, Arizona, USA


Abstract

“Tar balls” are amorphous, carbonaceous spherules that occur in the tropospheric aerosol as a result of biomass and biofuel burning. They form a distinct group of particles with diameters typically between 30 and 500 nm and readily identifiable with electron microscopy. Their lack of a turbostratic microstructure distinguishes them from soot, and their morphology and composition (∼90 mol % carbon) renders them distinct from other carbonaceous particles. Tar balls are particularly abundant in slightly aged (minutes to hours old) biomass smoke, indicating that they likely form by gas-to-particle conversion within smoke plumes. The material of tar balls is initially hygroscopic; however, the particles become largely insoluble as a result of free radical polymerization of their organic molecules. Consequently, tar balls are primarily externally mixed with other particle types, and they do not appreciably increase in size during aging. When tar balls coagulate with water-bearing particles, their material may partly dissolve and no longer be recognizable as distinct particles. Tar balls may contain organic compounds that absorb sunlight. They are an important, previously unrecognized type of carbonaceous (organic) atmospheric particle.

Received 17 September 2003; accepted 14 January 2004; published 27 March 2004.

Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry.

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Citation: Pósfai, M., A. Gelencsér, R. Simonics, K. Arató, J. Li, P. V. Hobbs, and P. R. Buseck (2004), Atmospheric tar balls: Particles from biomass and biofuel burning, J. Geophys. Res., 109, D06213, doi:10.1029/2003JD004169.