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Effects of sulfate coatings on the ice nucleation properties of a biological ice nucleus and several types of minerals. Bertram, Allan K.; Chernoff, Donna I.

Abstract

An optical microscope coupled to a flow cell was used to study the ice nucleation properties of uncoated and coated mineral dust and SNOMAX (a proxy for biological ice nucleators made from cells of Pseudomonas syringae) at temperatures ranging from 234 to 247 K. We define the onset conditions as the relative humidity (RH) and temperature at which the first ice nucleation event was observed. The results show that H2SO4 coatings modified the ice nucleation properties of all the minerals studied. For kaolinite and illite, the acid coatings increased the RH over ice (RHi) required for ice nucleation by ~30% RHi; for montmorillonite and quartz, the acid coatings increased the RHi by ~20% RHi. NH4HSO4 coatings also influenced the ice nucleation properties of kaolinite particles. In addition, our results indicate that SNOMAX is a reasonably good ice nucleus, having onset values between 110 to 120% RHi. In contrast to the mineral studies, sulfuric acid coatings did not hinder the ice nucleating ability of SNOMAX particles. Combined, our results support the idea that anthropogenic emissions of SO2 and NH3 may influence the ice-nucleating properties of mineral dust particles. From our laboratory data, we also determined contact angles (θ) between the heterogeneous nuclei and ice embryos according to classical nucleation theory to parameterize the laboratory data for inclusion in atmospheric models. The data show that for uncoated ice nuclei the contact angles are small (below ~20°), but for mineral particles coated with sulfuric acid, the contact angles are larger (above ~60°). An edited version of this paper was published by AGU. Copyright 2010 American Geophysical Union.

Item Metadata

Title
Effects of sulfate coatings on the ice nucleation properties of a biological ice nucleus and several types of minerals.
Creator
Bertram, Allan K.; Chernoff, Donna I.
Publisher
American Geophysical Union
Date Issued
2010-10
Description
An optical microscope coupled to a flow cell was used to study the ice nucleation properties of uncoated and coated mineral dust and SNOMAX (a proxy for biological ice nucleators made from cells of Pseudomonas syringae) at temperatures ranging from 234 to 247 K. We define the onset conditions as the relative humidity (RH) and temperature at which the first ice nucleation event was observed. The results show that H2SO4 coatings modified the ice nucleation properties of all the minerals studied. For kaolinite and illite, the acid coatings increased the RH over ice (RHi) required for ice nucleation by ~30% RHi; for montmorillonite and quartz, the acid coatings increased the RHi by ~20% RHi. NH4HSO4 coatings also influenced the ice nucleation properties of kaolinite particles. In addition, our results indicate that SNOMAX is a reasonably good ice nucleus, having onset values between 110 to 120% RHi. In contrast to the mineral studies, sulfuric acid coatings did not hinder the ice nucleating ability of SNOMAX particles. Combined, our results support the idea that anthropogenic emissions of SO2 and NH3 may influence the ice-nucleating properties of mineral dust particles. From our laboratory data, we also determined contact angles (θ) between the heterogeneous nuclei and ice embryos according to classical nucleation theory to parameterize the laboratory data for inclusion in atmospheric models. The data show that for uncoated ice nuclei the contact angles are small (below ~20°), but for mineral particles coated with sulfuric acid, the contact angles are larger (above ~60°). An edited version of this paper was published by AGU. Copyright 2010 American Geophysical Union.
Genre
Article
Type
Text
Language
eng
Date Available
2016-11-07
Provider
Vancouver : University of British Columbia Library
Rights
Attribution-NonCommercial-NoDerivatives 4.0 International
DOI
10.14288/1.0041865
URI
http://hdl.handle.net/2429/33690
Affiliation
Science, Faculty of; Chemistry, Department of
Citation
Effects of sulfate coatings on the ice nucleation properties of a biological ice nucleus and several types of minerals. 2010. Chernoff, Donna I., Bertram, Allan K. Journal of Geophysical Research Atmospheres 115(D20) D20205/1-D20205/12.
Publisher DOI
10.1029/2010JD014254
Peer Review Status
Reviewed
Scholarly Level
Faculty
Copyright Holder
Bertram, Allan K.
Rights URI
http://creativecommons.org/licenses/by-nc-nd/4.0/
Aggregated Source Repository
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Attribution-NonCommercial-NoDerivatives 4.0 International