Immersion freezing ability of freshly emitted soot with various physico-chemical characteristics

John Falk, Kimmo Korhonen, Vilhelm B. Malmborg, Louise Gren, Axel C. Eriksson, Panu Karjalainen, Lassi Markkula, Per Erik Bengtsson, Annele Virtanen, Birgitta Svenningsson, Joakim Pagels, Thomas B. Kristensen

Research output: Contribution to journalArticleScientificpeer-review

5 Downloads (Pure)

Abstract

The immersion freezing ability of soot particles has in previous studies been reported in the range of low/insignificant to very high. The aims of this study were to: (i) perform detailed physico-chemical characterisation of freshly produced soot particles with very different properties, (ii) investigate the immersion freezing ability of the same particles, and (iii) investigate the potential links between physico-chemical particle properties and ice-activity. A miniCAST soot generator was used to produce eight different soot samples representing a wide range of physico-chemical properties. A continuous flow diffusion chamber was used to study each sample online in immersion mode over the temperature (T) range from −41 to −32C, at a supersaturation of about 10% with respect to liquid water. All samples exhibited low to no heterogeneous immersion freezing. The most active sample reached ice-activated fractions (AF) of 10−3 and 10−4 at temperatures of 1.7 and 1.9 K, respectively, above the homogeneous freezing temperature. The samples were characterized online with respect to a wide range of physico-chemical properties including effective particle density, optical properties, particle surface oxidation and soot maturity. We did observe indications of increasing immersion freezing ice-activity with increasing effective particle density and increasing particulate PAH fraction . Hence, those properties, or other properties co-varying with those, could potentially enhance the immersion freezing ice-activity of the studied soot particle types. However, we found no significant correlation between the physico-chemical properties and the observed ice-nucleating ability when the particle ensemble was extended to include previously published results including more ice-active biomass combustion soot particles. We conclude that it does not appear possible in general and in any straightforward way to link observed soot particle physico-chemical properties to the ice-nucleating ability using the online instrumentation included in this study. Furthermore, our observations support that freshly produced soot particles with a wide range of physico-chemical properties have low to insignificant immersion freezing ice-nucleating ability.

Original languageEnglish
Article number1173
Number of pages17
JournalAtmosphere
Volume12
Issue number9
DOIs
Publication statusPublished - Sept 2021
Publication typeA1 Journal article-refereed

Keywords

  • Aerosol
  • Black carbon
  • Brown carbon
  • Ice nucleation
  • Immersion freezing
  • MiniCAST
  • Soot
  • SPIN

Publication forum classification

  • Publication forum level 1

ASJC Scopus subject areas

  • Environmental Science (miscellaneous)

Fingerprint

Dive into the research topics of 'Immersion freezing ability of freshly emitted soot with various physico-chemical characteristics'. Together they form a unique fingerprint.

Cite this