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<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>H.D. Easter</dc:contributor>
  <dc:contributor>Bettina M. Voelker</dc:contributor>
  <dc:creator>S.P. Hansard</dc:creator>
  <dc:date>2011</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;Superoxide radical (O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;) has been proposed to be an important participant in oxidation−reduction reactions of metal ions in natural waters. Here, we studied the reaction of nanomolar Mn(II) with O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;in seawater and simulated freshwater, using chemiluminescence detection of O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;to quantify the effect of Mn(II) on the decay kinetics of O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;. With 3−24 nM added [Mn(II)] and &amp;lt;0.7 nM [O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;], we observed effective second-order rate constants for the reaction of Mn(II) with O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;of 6 × 10&lt;/span&gt;&lt;sup&gt;6&lt;/sup&gt;&lt;span&gt;&amp;nbsp;to 1 × 10&lt;/span&gt;&lt;sup&gt;7&lt;/sup&gt;&lt;span&gt;&amp;nbsp;M&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;·s&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;&amp;nbsp;in various seawater samples. In simulated freshwater (pH 8.6), the effective rate constant of Mn(II) reaction with O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;was somewhat lower, 1.6 × 10&lt;/span&gt;&lt;sup&gt;6&lt;/sup&gt;&lt;span&gt;&amp;nbsp;M&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;·s&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;. With higher initial [O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;], in excess of added [Mn(II)], catalytic decay of O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;by Mn was observed, implying that a Mn(II/III) redox cycle occurred. Our results show that reactions with nanomolar Mn(II) could be an important sink of O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;in natural waters. In addition, reaction of Mn(II) with superoxide could maintain a significant fraction of dissolved Mn in the +III oxidation state.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1021/es104014s</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>American Chemical Society</dc:publisher>
  <dc:title>Rapid reaction of nanomolar Mn(II) with superoxide radical in seawater and simulated freshwater</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>