Ice Nucleation and Droplet Formation by Bare and Coated Black Carbon Particles

Journal Article · Thu Oct 13 04:00:00 EDT 2011 · Journal of Geophysical Research. D. (Atmospheres), 116:Article No. D17203

DOI:https://doi.org/10.1029/2011jd015999· OSTI ID:1036927

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

We have studied the ice formation at heterogeneous and homogeneous temperatures, 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 a 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 well characterized mineral dust particle that acts as an efficient ice nucleus, as well as 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, 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 from our studies that both uncoated and coated soot particles are unlikely to 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: 1036927
• Report Number(s): PNNL-SA-79084; KC0302020
• Journal Information: Journal of Geophysical Research. D. (Atmospheres), 116:Article No. D17203, Journal Name: Journal of Geophysical Research. D. (Atmospheres), 116:Article No. D17203 Vol. 116
• Country of Publication: United States
• Language: English

Related Subjects

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