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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>7</volume_number>
		<issue_number>3</issue_number>
		<publication_year>2007</publication_year>
	</journal>
	<doi>10.5194/acpd-7-6999-2007</doi>
	<article_url>http://www.atmos-chem-phys-discuss.net/7/6999/2007/</article_url>
	<abstract_html>http://www.atmos-chem-phys-discuss.net/7/6999/2007/acpd-7-6999-2007.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys-discuss.net/7/6999/2007/acpd-7-6999-2007.pdf</fulltext_pdf>
	<start_page>6999</start_page>
	<end_page>7034</end_page>
	<publication_date>2007-05-24</publication_date>
	<article_title content_type="html">Heterogeneous uptake of the C&lt;sub&gt;1&lt;/sub&gt; to C&lt;sub&gt;4&lt;/sub&gt; organic acids on a swelling clay mineral</article_title>
	<authors>
		<author numeration="1" affiliations="1">
			<name>C. D. Hatch</name>
		</author>
		<author numeration="2" affiliations="1">
			<name>R. V. Gough</name>
		</author>
		<author numeration="3" affiliations="1">
			<name>M. A. Tolbert</name>
			<email>margaret.tolbert@colorado.edu</email>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">University of Colorado, Department of Chemistry and Biochemistry and the Cooperative Institute for Research in Environmental Sciences, CIRES Room 318, Boulder, Colorado 80309, USA</affiliation>
	</affiliations>
	<abstract content_type="html">Mineral aerosol is of interest due to its physiochemical impacts on the
Earth&apos;s atmosphere. However, adsorbed organics could influence the chemical
and physical properties of atmospheric mineral particles and alter their
impact on the biosphere and climate. In this work, the heterogeneous uptake
of a series of small organic acids on the swelling clay, Na-montmorillonite,
was studied at 212 K as a function of relative humidity (RH), organic acid
pressure and clay mass. A high vacuum chamber equipped with a quadrupole
mass spectrometer and a transmission Fourier transform infrared spectrometer
was used to detect the gas and condensed phases, respectively. Sub-monolayer
coverage of organic acid on montmorillonite was observed under dry
conditions and relevant organic acid pressures. However, the organic acid
content increased significantly with increasing humidity. Additionally,
while the initial uptake efficiency was found to be independent of organic
acid pressure, it increased linearly with increasing clay mass. Thus, the
small masses studied allow access to the entire surface area of the clay
sample with minimal effects due to surface saturation. Results from this
study show that the initial uptake efficiency for n-butyric acid on the clay
increases by an order of magnitude as the RH is raised from 0% to 45%
RH at 212 K while the uptake of formic, acetic and propionic acids increase
only slightly at higher humidities. Additionally, the presence of organic
acids was found to slightly enhance the water content of the clay above
45% RH. Our results indicate that heterogeneous uptake of organic acids
on swelling clay minerals provides an important heterogeneous sink for these
species and may modify the cloud forming potential of the clay particles.</abstract>
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</article>

