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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACPD</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics Discussions</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACPD</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7375</issn>
<publisher><publisher-name>Copernicus GmbH</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acpd-7-383-2007</article-id>
<title-group>
<article-title>Ice nucleation of ammonia gas exposed montmorillonite mineral dust particles</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Salam</surname>
<given-names>A.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Lohmann</surname>
<given-names>U.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Lesins</surname>
<given-names>G.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Department of Chemistry, University of Dhaka, Dhaka &amp;ndash; 1000, Bangladesh</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Institute of Atmospheric and Climate Science, ETH Zurich, Switzerland</addr-line>
</aff>
<pub-date pub-type="epub">
<day>10</day>
<month>01</month>
<year>2007</year>
</pub-date>
<volume>7</volume>
<issue>1</issue>
<fpage>383</fpage>
<lpage>403</lpage>
<permissions>
<license xlink:type="simple">
<license-p>This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
</license>
</permissions>
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<self-uri xlink:href="http://www.atmos-chem-phys-discuss.net/7/383/2007/acpd-7-383-2007.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/7/383/2007/acpd-7-383-2007.pdf</self-uri>
<abstract>
<p>The ice nucleation characteristics of montmorillonite
mineral dust aerosols with and without exposure to ammonia gas were measured
at different atmospheric temperatures and relative humidities with a
continuous flow diffusion chamber. The montmorillonite particles were
exposed to pure (100%) and diluted ammonia gas (25 ppm) at room
temperature in a stainless steel chamber. There was no significant change in
the mineral dust particle size distribution due to the ammonia gas exposure.
100% pure ammonia gas exposure enhanced the ice nucleating fraction of
montmorillonite mineral dust particles 3 to 8 times at 90% relative
humidity with respect to water (RHw) and 5 to 8 times at 100% RHw for 120 min
exposure time within our experimental conditions. The percentages of
active ice nuclei were 2 to 9 times higher at 90% RHw and 2 to 13 times
higher at 100% RHw in 25 ppm ammonia exposed montmorillonite compared to
unexposed montmorillonite. All montmorillonite particles are more efficient
as ice nuclei with increasing relative humidities and decreasing
temperatures. The activation temperature of montmorillonite exposed to
100% pure ammonia was 12&amp;deg;C higher than for unexposed montmorillonite
particles at 90% RHw and 10&amp;deg;C higher at 100% RHw. In the 25 ppm
ammonia exposed montmorillonite experiments, the activation temperature was
7&amp;deg;C warmer than unexposed montmorillonite at 100% RHw. Degassing
does not reverse the ice nucleating ability of ammonia exposed
montmorillonite mineral dust particles. This is the first experimental
evidence that ammonia gas exposed montmorillonite mineral dust particles can
enhance its activation as ice nuclei and that the activation can occur at
temperatures warmer than &amp;ndash;10&amp;deg;C where natural atmospheric ice nuclei are
very scarce.</p>
</abstract>
<counts><page-count count="21"/></counts>
</article-meta>
</front>
<body/>
<back>
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</article>