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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>A. J. Tesoriero</dc:contributor>
  <dc:contributor>W. B. Richardson</dc:contributor>
  <dc:contributor>E.A. Strauss</dc:contributor>
  <dc:contributor>M.D. Munn</dc:contributor>
  <dc:creator>J.H. Duff</dc:creator>
  <dc:date>2008</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;Physical, chemical, hydrologic, and biologic factors affecting nitrate (NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;) removal were evaluated in three agricultural streams draining orchard/dairy and row crop settings. Using 3-d &amp;ldquo;snapshots&amp;rdquo; during biotically active periods, we estimated reach-level NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;sources, NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;mass balance, in-stream processing (nitrification, denitrification, and NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;uptake), and NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;retention potential associated with surface water transport and ground water discharge. Ground water contributed 5 to 11% to stream discharge along the study reaches and 8 to 42% of gross NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;input. Streambed processes potentially reduced 45 to 75% of ground water NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;before discharge to surface water. In all streams, transient storage was of little importance for surface water NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;retention. Estimated nitrification (1.6&amp;ndash;4.4 mg N m&lt;/span&gt;&lt;sup&gt;&amp;minus;2&lt;/sup&gt;&lt;span&gt;&amp;nbsp;h&lt;/span&gt;&lt;sup&gt;&amp;minus;1&lt;/sup&gt;&lt;span&gt;) and unamended denitrification rates (2.0&amp;ndash;16.3 mg N m&lt;/span&gt;&lt;sup&gt;&amp;minus;2&lt;/sup&gt;&lt;span&gt;&amp;nbsp;h&lt;/span&gt;&lt;sup&gt;&amp;minus;1&lt;/sup&gt;&lt;span&gt;) in sediment slurries were high relative to pristine streams. Denitrification of NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;was largely independent of nitrification because both stream and ground water were sources of NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;Unamended denitrification rates extrapolated to the reach-scale accounted for &amp;lt;5% of NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;exported from the reaches minimally reducing downstream loads. Nitrate retention as a percentage of gross NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;inputs was &amp;gt;30% in an organic-poor, autotrophic stream with the lowest denitrification potentials and highest benthic chlorophyll&amp;nbsp;&lt;/span&gt;&lt;i&gt;a&lt;/i&gt;&lt;span&gt;, photosynthesis/respiration ratio, pH, dissolved oxygen, and diurnal NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;variation. Biotic processing potentially removed 75% of ground water NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;at this site, suggesting an important role for photosynthetic assimilation of ground water NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;relative to subsurface denitrification as water passed directly through benthic diatom beds.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.2134/jeq2007.0187</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>ACSESS</dc:publisher>
  <dc:title>Whole-stream response to nitrate loading in three streams draining agricultural landscapes</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>