Not all feldspars are equal: a survey of ice nucleating properties across the feldspar group of minerals
Mineral dust particles from wind-blown soils are known to act as effective ice nucleating particles in the atmosphere and are thought to play an important role in the glaciation of mixed phase clouds. Recent work suggests that feldspars are the most efficient nucleators of the minerals commonly...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/10927/2016/acp-16-10927-2016.pdf |
| Summary: | Mineral dust particles from wind-blown soils are known to act as effective
ice nucleating particles in the atmosphere and are thought to play an
important role in the glaciation of mixed phase clouds. Recent work suggests
that feldspars are the most efficient nucleators of the minerals commonly
present in atmospheric mineral dust. However, the feldspar group of minerals
is complex, encompassing a range of chemical compositions and crystal
structures. To further investigate the ice-nucleating properties of the
feldspar group we measured the ice nucleation activities of 15 characterized
feldspar samples. We show that alkali feldspars, in particular the potassium
feldspars, generally nucleate ice more efficiently than feldspars in the
plagioclase series which contain significant amounts of calcium. We also
find that there is variability in ice nucleating ability within these
groups. While five out of six potassium-rich feldspars have a similar ice
nucleating ability, one potassium rich feldspar sample and one sodium-rich
feldspar sample were significantly more active. The hyper-active Na-feldspar
was found to lose activity with time suspended in water with a decrease in
mean freezing temperature of about 16 °C over 16 months; the mean
freezing temperature of the hyper-active K-feldspar decreased by
2 °C over 16 months, whereas the "standard" K-feldspar did not
change activity within the uncertainty of the experiment. These results, in
combination with a review of the available literature data, are consistent
with the previous findings that potassium feldspars are important components
of arid or fertile soil dusts for ice nucleation. However, we also show that
there is the possibility that some alkali feldspars may have enhanced ice
nucleating abilities, which could have implications for prediction of ice
nucleating particle concentrations in the atmosphere. |
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| ISSN: | 1680-7316 1680-7324 |