Ice nucleation abilities of soot particles determined with the Horizontal Ice Nucleation Chamber

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Date
2018Type
- Journal Article
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Cited 49 times in
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Cited 57 times in
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Abstract
Ice nucleation by different types of soot particles is systematically investigated over the temperature range from 218 to 253K relevant for both mixed-phase (MPCs) and cirrus clouds. Soot types were selected to represent a range of physicochemical properties associated with combustion particles. Their ice nucleation ability was determined as a function of particle size using relative humidity (RH) scans in the Horizontal Ice Nucleation Chamber (HINC). We complement our ice nucleation results by a suite of particle characterization measurements, including determination of particle surface area, fractal dimension, temperature-dependent mass loss (ML), water vapor sorption and inferred porosity measurements. Independent of particle size, all soot types reveal absence of ice nucleation below and at water saturation in the MPC regime (T > 235K). In the cirrus regime (T ≤ 235K), soot types show different freezing behavior depending on particle size and soot type, but the freezing is closely linked to the soot particle properties. Specifically, our results suggest that if soot aggregates contain mesopores (pore diameters of 2–50nm) and have sufficiently low water–soot contact angles, they show ice nucleation activity and can contribute to ice formation in the cirrus regime at RH well below homogeneous freezing of solution droplets. We attribute the observed ice nucleation to a pore condensation and freezing (PCF) mechanism. Nevertheless, soot particles without cavities of the right size and/or too-high contact angles nucleate ice only at or well above the RH required for homogeneous freezing conditions of solution droplets. Thus, our results imply that soot particles able to nucleate ice via PCF could impact the microphysical properties of ice clouds. Show more
Permanent link
https://doi.org/10.3929/ethz-b-000293175Publication status
publishedExternal links
Journal / series
Atmospheric Chemistry and PhysicsVolume
Pages / Article No.
Publisher
CopernicusOrganisational unit
03690 - Lohmann, Ulrike / Lohmann, Ulrike
03917 - Burgert, Ingo / Burgert, Ingo
02891 - ScopeM / ScopeM
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Show all metadata
Citations
Cited 49 times in
Web of Science
Cited 57 times in
Scopus
ETH Bibliography
yes
Altmetrics