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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-9-721-2009</article-id>
<title-group>
<article-title>Analysis of the hygroscopic and volatile properties of ammonium sulphate seeded and unseeded SOA particles</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Meyer</surname>
<given-names>N. K.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Duplissy</surname>
<given-names>J.</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>Gysel</surname>
<given-names>M.</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>Metzger</surname>
<given-names>A.</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>Dommen</surname>
<given-names>J.</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>Weingartner</surname>
<given-names>E.</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>Alfarra</surname>
<given-names>M. R.</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>Prevot</surname>
<given-names>A. S. H.</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>Fletcher</surname>
<given-names>C.</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>Good</surname>
<given-names>N.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>McFiggans</surname>
<given-names>G.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Jonsson</surname>
<given-names>Å. M.</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Hallquist</surname>
<given-names>M.</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Baltensperger</surname>
<given-names>U.</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>Ristovski</surname>
<given-names>Z. D.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane QLD 4000, Australia</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Centre for Atmospheric Sciences, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M60 1QD, UK</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Department of Chemistry, Atmospheric Science, University of Gothenburg, 412 96 Gothenburg, Sweden</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>now at: IAST, FHNW University of Applied Sciences, Windisch 5210, Switzerland</addr-line>
</aff>
<pub-date pub-type="epub">
<day>28</day>
<month>01</month>
<year>2009</year>
</pub-date>
<volume>9</volume>
<issue>2</issue>
<fpage>721</fpage>
<lpage>732</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/9/721/2009/acp-9-721-2009.html">This article is available from http://www.atmos-chem-phys.net/9/721/2009/acp-9-721-2009.html</self-uri>
<self-uri xlink:href="http://www.atmos-chem-phys.net/9/721/2009/acp-9-721-2009.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/721/2009/acp-9-721-2009.pdf</self-uri>
<abstract>
<p>The volatile and hygroscopic properties of ammonium sulphate seeded and
unseeded secondary organic aerosol (SOA) derived from the photo-oxidation
of atmospherically relevant concentrations of α-pinene were studied.
The seed particles were electrospray generated ammonium sulphate
((NH4)&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;) having diameters of approximately 33 nm with a
quasi-mono-disperse size distribution (geometric standard deviation &amp;sigma;&lt;sub&gt;g&lt;/sub&gt;=1.3).
The volatile and hygroscopic properties of both seeded and
unseeded SOA were simultaneously measured with a VH-TDMA (volatility –
hygroscopicity tandem differential mobility analyzer). VH-TDMA
measurements of unseeded SOA show a decrease in the hygroscopic growth (HGF)
factor for increased volatilisation temperatures such that the more volatile
compounds appear to be more hygroscopic. This is opposite to the expected
preferential evaporation of more volatile but less hygroscopic material, but
could also be due to enhanced oligomerisation occurring at the higher
temperature in the thermodenuder. In addition, HGF measurements of seeded
SOA were measured as a function of time at two relative humidities, below
(RH 75%) and above (RH 85%) the deliquescence relative humidity (DRH)
of the pure ammonium sulphate seeds. As these measurements were conducted
during the onset phase of photo-oxidation, during particle growth, they
enabled us to find the dependence of the HGF as a function of the volume
fraction of the SOA coating. HGF&apos;s measured at RH of 85% showed a
continuous decrease as the SOA coating thickness increased. The measured
growth factors show good agreements with ZSR predictions indicating that, at
these RH values, there are only minor solute-solute interactions. At 75%
RH, as the SOA fraction increased, a rapid increase in the HGF was observed
indicating that an increasing fraction of the (NH&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt; is
subject to a phase transition, going into solution, with an increasing
volume fraction of SOA. To our knowledge this is the first time that SOA
derived from photo-oxidised α-pinene has been shown to affect the
equilibrium water content of inorganic aerosols below their DRH. For SOA
volume fractions above ~0.3 the measured growth factor followed
roughly parallel to the ZSR prediction based on fully dissolved
(NH&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt; although with a small difference that was just
larger than the error estimate. Both incomplete dissolution and negative
solute-solute interactions could be responsible for the lower HGF observed
compared to the ZSR predictions.</p>
</abstract>
<counts><page-count count="12"/></counts>
</article-meta>
</front>
<body/>
<back>
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