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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>M.A. Mikita</dc:contributor>
  <dc:creator>K. A. Thorn</dc:creator>
  <dc:date>2000</dc:date>
  <dc:description>&lt;p&gt;Studies have suggested that NO&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;, produced during nitrification and denitrification, can become incorporated into soil organic matter and, in one of the processes associated with chemodenitrification, react with organic matter to form trace N gases, including N&lt;sub&gt;2&lt;/sub&gt;O. To gain an understanding of the nitrosation chemistry on a molecular level, soil and aquatic humic substances were reacted with&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;N-labeled NaNO&lt;sub&gt;2&lt;/sub&gt;, and analyzed by liquid phase&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;N and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;13&lt;/sup&gt;C nuclear magnetic resonance (NMR). The International Humic Substances Society (IHSS) Pahokee peat and peat humic acid were also reacted with Na&lt;sup&gt;15&lt;/sup&gt;NO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and analyzed by solid-state&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;N NMR. In Suwannee River, Armadale, and Laurentian fulvic acids, phenolic rings and activated methylene groups underwent nitrosation to form nitrosophenols (quinone monoximes) and ketoximes, respectively. The oximes underwent Beckmann rearrangements to 2° amides, and Beckmann fragmentations to nitriles. The nitriles in turn underwent hydrolysis to 1° amides. Peaks tentatively identified as imine, indophenol, or azoxybenzene nitrogens were clearly present in spectra of samples nitrosated at pH 6 but diminished at pH 3. The&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;N NMR spectrum of the peat humic acid exhibited peaks corresponding with N-nitroso groups in addition to nitrosophenols, ketoximes, and secondary Beckmann reaction products. Formation of N-nitroso groups was more significant in the whole peat compared with the peat humic acid. Carbon-13 NMR analyses also indicated the occurrence of nitrosative demethoxylation in peat and soil humic acids. Reaction of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;N-NH&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;fixated fulvic acid with unlabeled NO&lt;sup&gt;−&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;resulted in nitrosative deamination of aminohydroquinone N, suggesting a previously unrecognized pathway for production of N&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;gas in soils fertilized with NH&lt;sub&gt;3&lt;/sub&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.2136/sssaj2000.642568x</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Soil Science Society of America</dc:publisher>
  <dc:title>Nitrite fixation by humic substances: Nitrogen-15 nuclear magnetic resonance evidence for potential intermediates in chemodenitrification</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>