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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACP</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACP</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7324</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/acp-5-2679-2005</article-id>
<title-group>
<article-title>The uptake of SO&lt;sub&gt;2&lt;/sub&gt; on Saharan dust: a flow tube study</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Adams</surname>
<given-names>J. W.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Rodriguez</surname>
<given-names>D.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Cox</surname>
<given-names>R. A.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Centre for Atmospheric Science, Chemistry Department, University of Cambridge, UK</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Facultad de Ciencias del Medio Ambiente, Departamento de Quimica Fisica, Universidad de Castilla-La Mancha, Avda. Carlos III s/n, Campus Tecnologico, 45071-Toledo, Spain</addr-line>
</aff>
<pub-date pub-type="epub">
<day>12</day>
<month>12</month>
<year>2005</year>
</pub-date>
<volume>5</volume>
<issue>10</issue>
<fpage>2679</fpage>
<lpage>2689</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>
<self-uri xlink:href="http://www.atmos-chem-phys.net/5/2679/2005/acp-5-2679-2005.html">This article is available from http://www.atmos-chem-phys.net/5/2679/2005/acp-5-2679-2005.html</self-uri>
<self-uri xlink:href="http://www.atmos-chem-phys.net/5/2679/2005/acp-5-2679-2005.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/5/2679/2005/acp-5-2679-2005.pdf</self-uri>
<abstract>
<p>The uptake of SO&lt;sub&gt;2&lt;/sub&gt; onto Saharan mineral dust from the Cape Verde Islands
was investigated using a coated wall flow tube coupled to a mass
spectrometer. The rate of loss of SO&lt;sub&gt;2&lt;/sub&gt; to the dust coating was measured
and uptake coefficients were determined using the measured BET surface area
of the sample. The uptake of SO&lt;sub&gt;2&lt;/sub&gt;, with an initial concentration between
(2-40)x10&lt;sup&gt;10&lt;/sup&gt;molecule cm&lt;sup&gt;-3&lt;/sup&gt; (0.62-12 &amp;micro;Torr), was found
to be strongly time dependent over the first few hundred seconds of an
experiment, with an initial uptake &amp;gamma;&lt;sub&gt;0,BET&lt;/sub&gt; of (6.6&amp;plusmn;0.8)x10&lt;sup&gt;-5&lt;/sup&gt; (298 K), declining at longer times. The amount of
SO&lt;sub&gt;2&lt;/sub&gt; adsorbed on the dust samples was measured over a range of SO&lt;sub&gt;2&lt;/sub&gt; concentrations and mineral dust loadings. The uptake of SO&lt;sub&gt;2&lt;/sub&gt;
was found to be up to 98% irreversible over the timescale of these
investigations. Experiments were also performed at 258 K, at a relative
humidity of 27% and at 298 K in the presence of ozone. The initial uptake
and the amount of SO&lt;sub&gt;2&lt;/sub&gt; taken up per unit area of BET dust surface was
the same within error, irrespective of the conditions used; however the
presence of ozone reduced the amount of SO&lt;sub&gt;2&lt;/sub&gt; released back into the
gas-phase per unit area once exposure of the surface ended. Multiple uptakes
to the same surface revealed a loss of surface reactivity, which did not
return if the samples were exposed to gas-phase water, or left under vacuum
overnight. A mechanism which accounts for the observed uptake behaviour is
proposed and numerically modelled, allowing quantitative estimates of the
rate and amount of SO&lt;sub&gt;2&lt;/sub&gt; removal in the atmosphere to be estimated.
Removal of SO&lt;sub&gt;2&lt;/sub&gt; by mineral dust is predicted to be significant at high
dust loadings.</p>
</abstract>
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