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

Falk, John LU ; Korhonen, Kimmo LU ; Malmborg, Vilhelm B. LU orcid ; Gren, Louise LU ; Eriksson, Axel C. LU orcid ; Karjalainen, Panu LU ; Markkula, Lassi ; Bengtsson, Per Erik LU orcid ; Virtanen, Annele and Svenningsson, Birgitta LU , et al. (2021) In Atmosphere 12(9).
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... (More)

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 −32◦C, 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.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Aerosol, Black carbon, Brown carbon, Ice nucleation, Immersion freezing, MiniCAST, Soot, SPIN
in
Atmosphere
volume
12
issue
9
article number
1173
publisher
MDPI AG
external identifiers
  • scopus:85115219176
ISSN
2073-4433
DOI
10.3390/atmos12091173
language
English
LU publication?
yes
additional info
Funding Information: Funding: This project was funded by Formas (grant number 2015-00992), Swedish Research Council VR (grant number 2017-05016; J.P., V.M., A.E. and L.G. were funded by grant number 2018-04200). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.
id
bcafd3da-6353-4959-8f44-efc79b130da2
date added to LUP
2021-09-29 09:02:45
date last changed
2023-11-08 19:58:36
@article{bcafd3da-6353-4959-8f44-efc79b130da2,
  abstract     = {{<p>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 −32<sup>◦</sup>C, 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<sup>−3</sup> and 10<sup>−4</sup> 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.</p>}},
  author       = {{Falk, John and Korhonen, Kimmo and Malmborg, Vilhelm B. and Gren, Louise and Eriksson, Axel C. and Karjalainen, Panu and Markkula, Lassi and Bengtsson, Per Erik and Virtanen, Annele and Svenningsson, Birgitta and Pagels, Joakim and Kristensen, Thomas B.}},
  issn         = {{2073-4433}},
  keywords     = {{Aerosol; Black carbon; Brown carbon; Ice nucleation; Immersion freezing; MiniCAST; Soot; SPIN}},
  language     = {{eng}},
  number       = {{9}},
  publisher    = {{MDPI AG}},
  series       = {{Atmosphere}},
  title        = {{Immersion freezing ability of freshly emitted soot with various physico-chemical characteristics}},
  url          = {{http://dx.doi.org/10.3390/atmos12091173}},
  doi          = {{10.3390/atmos12091173}},
  volume       = {{12}},
  year         = {{2021}},
}