<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>D. Kip Solomon</dc:contributor>
  <dc:contributor>Robert J. Poreda</dc:contributor>
  <dc:contributor>Andrew G. Hunt</dc:contributor>
  <dc:creator>Amy L. Sheldon</dc:creator>
  <dc:date>2003</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;Profiles of&amp;nbsp;&lt;/span&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;span&gt;He in pore water were measured in clay aquitards in SW Ontario. The&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;span&gt;He distributions are consistent with groundwater velocities that are &amp;lt;6 mm yr&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;, and thus diffusion is the dominant transport mechanism for&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;span&gt;He. Modeling indicates that the effective diffusion coefficient for&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;span&gt;He is 6.3 ± 1.6 × 10&lt;/span&gt;&lt;sup&gt;−6&lt;/sup&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;cm&lt;/span&gt;&lt;sup&gt;2&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;s&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;. Furthermore, the profiles are consistent with the internal release of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;span&gt;He from aquitard sediments at a rate of 0.03–0.13 μcc(STP) kg&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;yr&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;. These rates are also consistent with laboratory release experiments and, on average, are 600 times greater than the production of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;span&gt;He from U/Th decay. Modeling and the ratio of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;21&lt;/sup&gt;&lt;span&gt;Ne to&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;span&gt;He within the sediments indicate that although the aquitards were deposited about 13 kA BP, the sediments released &amp;gt;70% of initial&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;span&gt;He for 50 to 60 kA prior to incorporation into the till.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1029/2002WR001797</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>American Geophysical Union</dc:publisher>
  <dc:title>Radiogenic helium in shallow groundwater within a clay till, southwestern Ontario</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>