Organic matter matters for ice nuclei of agricultural soil origin
Heterogeneous ice nucleation is a crucial process for forming ice-containing clouds and subsequent ice-induced precipitation. The importance for ice nucleation by airborne desert soil dusts composed predominantly of minerals is widely acknowledged. However, the potential influence of agricultural so...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/14/8521/2014/acp-14-8521-2014.pdf |
| Summary: | Heterogeneous ice nucleation is a crucial process for forming ice-containing
clouds and subsequent ice-induced precipitation. The importance for ice
nucleation by airborne desert soil dusts composed predominantly of minerals
is widely acknowledged. However, the potential influence of
agricultural soil dusts on ice nucleation has been poorly recognized,
despite recent estimates that they may account for up to 20–25% of the global atmospheric dust load. We have conducted freezing
experiments with various dusts, including agricultural soil dusts derived
from the largest dust-source region in North America. Here we show evidence
for the significant role of soil organic matter (SOM) in particles acting as
ice nuclei (IN) under mixed-phase cloud conditions. We find that the ice-nucleating ability of the agricultural soil dusts is similar to that of
desert soil dusts, but is clearly reduced after either H<sub>2</sub>O<sub>2</sub>
digestion or dry heating to 300 °C. In addition, based on chemical
composition analysis, we demonstrate that organic-rich particles are more
important than mineral particles for the ice-nucleating ability of the
agricultural soil dusts at temperatures warmer than about −36 °C.
Finally, we suggest that such organic-rich particles of agricultural origin
(namely, SOM particles) may contribute significantly to the ubiquity of
organic-rich IN in the global atmosphere. |
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| ISSN: | 1680-7316 1680-7324 |