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<article language="en">
	<journal>
		<journal_title>Atmospheric Chemistry and Physics Discussions</journal_title>
		<journal_url>www.atmos-chem-phys-discuss.net</journal_url>
		<issn>1680-7367</issn>
		<eissn>1680-7375</eissn>
		<volume_number>10</volume_number>
		<issue_number>2</issue_number>
		<publication_year>2010</publication_year>
	</journal>
	<doi>10.5194/acpd-10-3129-2010</doi>
	<article_url>http://www.atmos-chem-phys-discuss.net/10/3129/2010/</article_url>
	<abstract_html>http://www.atmos-chem-phys-discuss.net/10/3129/2010/acpd-10-3129-2010.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys-discuss.net/10/3129/2010/acpd-10-3129-2010.pdf</fulltext_pdf>
	<start_page>3129</start_page>
	<end_page>3172</end_page>
	<publication_date>2010-02-05</publication_date>
	<article_title content_type="html">Influence of relative humidity and temperature on the production of  pinonaldehyde and OH radicals from the ozonolysis of &amp;alpha;-pinene</article_title>
	<authors>
		<author numeration="1" affiliations="1">
			<name>R. Tillmann</name>
		</author>
		<author numeration="2" affiliations="2">
			<name>M. Hallquist</name>
		</author>
		<author numeration="3" affiliations="2,5">
			<name>Å. M. Jonsson</name>
		</author>
		<author numeration="4" affiliations="1">
			<name>A. Kiendler-Scharr</name>
		</author>
		<author numeration="5" affiliations="3">
			<name>H. Saathoff</name>
		</author>
		<author numeration="6" affiliations="4">
			<name>Y. Iinuma</name>
		</author>
		<author numeration="7" affiliations="1">
			<name>Th. F. Mentel</name>
			<email>t.mentel@fz-juelich.de</email>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Institut für Chemie und Dynamik der Geosphäre 2,  Forschungszentrum Jülich, 52425 Jülich, Germany</affiliation>
		<affiliation numeration="2" content_type="html">Department of Chemistry, Atmospheric Science, University of  Gothenburg, 41296 Gothenburg, Sweden</affiliation>
		<affiliation numeration="3" content_type="html">Institute for Meteorology and Climate Research, Forschungszentrum Karlsruhe,  Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany</affiliation>
		<affiliation numeration="4" content_type="html">Leibnitz Institute for Tropospheric Research, Permoserstr. 15, 04318 Leipzig,  Germany</affiliation>
		<affiliation numeration="5" content_type="html">present address: IVL Swedish Environmental Research Institute Ltd,  Aschebergsgatan 44, 41133 Gothenburg, Sweden</affiliation>
	</affiliations>
	<abstract content_type="html">The ozonolysis of &amp;alpha;-pinene has been investigated under dry and
      humid conditions in the temperature range of 243–303 K. The results
      provided new insight into the role of water and temperature in the
      degradation mechanism of α-pinene and in the formation of
      secondary organic aerosols (SOA). The SOA yields were higher at humid
      conditions than at dry conditions. The water induced gain was largest
      for the lowest temperatures investigated (243 and 253 K). The
      increase in the SOA yields was dominated by water (and temperature)
      effects on the organic product distribution, whilst physical uptake of
      water was negligible. This will be demonstrated for the example of
      pinonaldehyde (PA) which was formed as a~major product in the humid
      experiments with total molar yields of 0.30&amp;plusmn;0.06 at 303 K and
      0.15&amp;plusmn;0.03 at 243 K. In the dry experiments the molar yields of PA
      were only 0.07&amp;plusmn;0.02 at 303 K and 0.02&amp;plusmn;0.02 at 253 K. The
      observed partitioning of PA as a function of the SOA mass present at
      303 K limited the effective vapour pressure of pure PA &lt;i&gt;p&lt;/i&gt;&lt;sub&gt;PA&lt;/sub&gt;&lt;sup&gt;0&lt;/sup&gt;
      to the range of 0.01–0.001 Pa, 3–4 orders of magnitude lower than
      literature values. The corresponding mass partitioning coefficient was
      determined to &lt;i&gt;K&lt;/i&gt;&lt;sub&gt;PA&lt;/sub&gt;=0.005&amp;plusmn;0.004 m&lt;sup&gt;3&lt;/sup&gt;/&amp;mu;g and
      the total mass yield &amp;alpha;&lt;sub&gt;PA.total&lt;/sub&gt;=0.37&amp;plusmn;0.08. At
      303 K PA preferably stayed in the gas-phase, whereas at 253 K and
      243 K it exclusively partitioned into the particulate phase. PA could
      thus account at least for half of the water induced gain in SOA mass
      at 253 K. The corresponding effect was negligible at 303 K because
      the PA preferably remained in the gas-phase.
&lt;br&gt;&lt;br&gt;
      The yield of OH radicals, which were produced in the ozonolysis, was
      indirectly determined by means of the yield of cyclohexanone formed in
      the reaction of OH radicals with cyclohexane. OH yields of the
      α-pinene ozonolysis were determined to 0.67&amp;plusmn;0.17 for humid
      and 0.54&amp;plusmn;0.13 for dry conditions at 303 K, indicating a water
      dependent path of OH radical formation. For 253 and 243 K OH yields
      could be estimated to 0.5 with no significant difference between the
      dry and humid experiments. This is the first clear indication for OH
      radical formation by α-pinene ozonolysis at such low
      temperatures.</abstract>
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