Ice Nucleation and Droplet Formation by Bare and Coated Soot Particles

Journal Article · Tue Sep 13 04:00:00 EDT 2011 · Journal of Geophysical Research. D. (Atmospheres)

DOI:https://doi.org/10.1029/2011JD015999· OSTI ID:1027167

Friedman, Beth J; Kulkarni, Gourihar R; Beranek, Josef; Zelenyuk, Alla; Thornton, Joel A; Cziczo, Daniel J

We have studied ice formation at temperatures relevant to homogeneous and heterogeneous ice nucleation, as well as droplet activation and hygroscopicity, of soot particles of variable size and composition. Coatings of adipic, malic, and oleic acid were applied to span an atmospherically relevant range of solubility, and both uncoated and oleic acid coated soot particles were exposed to ozone to simulate atmospheric oxidation. The results are interpreted in terms of onset ice nucleation, with a comparison to a mineral dust particle that acts as an efficient ice nucleus, and particle hygroscopicity. At 253K and 243K, we found no evidence of heterogeneous ice nucleation occurring above the level of detection for our experimental conditions. Above water saturation, only droplet formation was observed. At 233K, we observe the occurrence of homogeneous ice nucleation for all particles studied. Coatings also did not significantly alter the ice nucleation behavior of soot particles, but aided in the uptake of water. Hygroscopicity studies confirmed that pure soot particles were hydrophobic, and coated soot particles activated as droplets at high water supersaturations. A small amount of heterogeneous ice nucleation either below the detection limit of our instrument or concurrent with droplet formation and/or homogeneous freezing cannot be precluded, but we are able to set limits for its frequency. We conclude that both uncoated and coated soot particles representative of those generated in our studies are unlikely to significantly contribute to the global budget of heterogeneous ice nuclei at temperatures between 233K and 253K.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1027167
• Report Number(s): PNNL-SA-82777
• Journal Information: Journal of Geophysical Research. D. (Atmospheres), Journal Name: Journal of Geophysical Research. D. (Atmospheres) Vol. 116
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
COATINGS
DETECTION
DUSTS
FREEZING
HYGROSCOPICITY
NUCLEATION
NUCLEI
OLEIC ACID
OXIDATION
OZONE
SENSITIVITY
SOLUBILITY
SOOT
WATER
WATER SATURATION