<?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>C. Kendall</dc:contributor>
  <dc:contributor>D.H. Wilkison</dc:contributor>
  <dc:contributor>A.C. Ziegler</dc:contributor>
  <dc:contributor>Cecily C.Y. Chang</dc:contributor>
  <dc:contributor>R.J. Avanzino</dc:contributor>
  <dc:creator>S. R. Silva</dc:creator>
  <dc:date>2000</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;A new method for concentrating&amp;nbsp;nitrate&amp;nbsp;from fresh waters for&amp;nbsp;&lt;/span&gt;&lt;i&gt;δ&lt;/i&gt;&lt;sup&gt;15&lt;/sup&gt;N and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;δ&lt;/i&gt;&lt;sup&gt;18&lt;/sup&gt;&lt;span&gt;O analysis has been developed and field-tested for four years. The benefits of the method are: (1) elimination of the need to transport large volumes of water to the laboratory for processing; (2) elimination of the need for hazardous&amp;nbsp;preservatives; and (3) the ability to concentrate nitrate from fresh waters. Nitrate is collected by, passing the water-sample through pre-filled, disposable,&amp;nbsp;anion&amp;nbsp;exchanging&amp;nbsp;resin&amp;nbsp;columns in the field. The columns are subsequently transported to the laboratory where the nitrate is extracted, converted to AgNO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and analyzed for its isotope composition. Nitrate is eluted from the anion exchange columns with 15&amp;nbsp;ml of 3&amp;nbsp;M HCl. The nitrate-bearing acid eluant is neutralized with Ag&lt;sub&gt;2&lt;/sub&gt;O, filtered to remove the AgCl precipitate, then freeze-dried to obtain solid AgNO&lt;sub&gt;3&lt;/sub&gt;, which is then combusted to N&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;in sealed&amp;nbsp;quartz&amp;nbsp;tubes for&amp;nbsp;&lt;/span&gt;&lt;i&gt;δ&lt;/i&gt;&lt;sup&gt;15&lt;/sup&gt;N analysis. For&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;δ&lt;/i&gt;&lt;sup&gt;18&lt;/sup&gt;&lt;span&gt;O analysis, aliquots of the neutralized eluant are processed further to remove non-nitrate oxygen-bearing anions and dissolved organic matter.&amp;nbsp;Barium&amp;nbsp;chloride is added to precipitate&amp;nbsp;sulfate&amp;nbsp;and phosphate; the solution is then filtered, passed through a cation exchange column to remove excess Ba&lt;/span&gt;&lt;sup&gt;2+&lt;/sup&gt;, re-neutralized with Ag&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O, filtered, agitated with&amp;nbsp;activated carbon&amp;nbsp;to remove dissolved organic matter and freeze-dried. The resulting AgNO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;is combusted with&amp;nbsp;graphite&amp;nbsp;in a closed tube to produce CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;, which is cryogenically purified and analyzed for its&amp;nbsp;oxygen isotope&amp;nbsp;composition. The 1&lt;/span&gt;&lt;i&gt;σ&lt;/i&gt;analytical precisions for&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;δ&lt;/i&gt;&lt;sup&gt;15&lt;/sup&gt;N and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;δ&lt;/i&gt;&lt;sup&gt;18&lt;/sup&gt;O are ±0.05‰ and ±0.5‰, respectively, for solutions of KNO&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;standard processed through the entire column procedure.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/S0022-1694(99)00205-X</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Elsevier</dc:publisher>
  <dc:title>A new method for collection of nitrate from fresh water and the analysis of nitrogen and oxygen isotope ratios</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>