<?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:creator>W. G. Wright</dc:creator>
  <dc:date>1999</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;Selenium (Se) can be oxidized by nitrate (NO&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;) from irrigation on Cretaceous marine shale in western Colorado. Dissolved Se concentrations are positively correlated with dissolved NO&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;concentrations in surface water and ground water samples from irrigated areas. Redox conditions dominate in the mobilization of Se in marine shale hydrogeologic settings; dissolved Se concentrations increase with increasing platinum-electrode potentials. Theoretical calculations for the oxidation of Se by NO&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;and oxygen show favorable Gibbs free energies for the oxidation of Se by NO&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;, indicating NO&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;can act as an electron acceptor for the oxidation of Se. Laboratory batch experiments were performed by adding Mancos Shale samples to zero-dissolved-oxygen water containing 0, 5, 50, and 100 mg/L NO&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;as N (mg N/L). Samples were incubated in airtight bottles at 25°C for 188 d; samples collected from the batch experiment bottles show increased Se concentrations over time with increased NO&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;concentrations. Pseudo first-order rate constants for NO&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;oxidation of Se ranged from 0.0007 to 0.0048/d for 0 to 100 mg N/L NO&lt;/span&gt;&lt;sup&gt;−&lt;/sup&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;concentrations, respectively. Management of N fertilizer applications in Cretaceous shale settings might help to control the oxidation and mobilization of Se and other trace constituents into the environment.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.2134/jeq1999.00472425002800040019x</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>ACSESS</dc:publisher>
  <dc:title>Oxidation and mobilization of selenium by nitrate in irrigation drainage</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>