Use of Isotope Abundance of <sup>15</sup>NO<sub>3</sub>-N in a Nitrate Rich Stream Below a Wastewater Treatment Plant to Evaluate Denitrification <p> HR: <span class="hr"> 1330h<br></span> AN: <span class="an"> NB33L-09 <a href="../absbook/sm05_NB33L.html">[Abstracts]</a><br></span> TI: <span class="ti"> Use of Isotope Abundance of <sup>15</sup>NO<sub>3</sub>-N in a Nitrate Rich Stream Below a Wastewater Treatment Plant to Evaluate Denitrification <br></span> AU: <span class="au"> * Lofton, D <br></span> EM: <span class="em"> ddlofton@uncg.edu<br></span> AF: <span class="af"> University of North Carolina-Greensboro, 343 Eberhart Building, Greensboro, NC 27402 United States <br></span> AU: <span class="au"> Hershey, A E<br></span> EM: <span class="em"> aehershe@uncg.edu<br></span> AF: <span class="af"> University of North Carolina-Greensboro, 343 Eberhart Building, Greensboro, NC 27402 United States <br></span> AB: <span class="ab"> Using natural isotope abundances of nitrate-nitrogen, in conjunction with nitrate concentrations along a stream transect, can provide information about nitrate input versus downstream export and losses due to denitrification. Given that denitrifying microbes prefer the lighter isotope, isotopic fractionation should occur in nitrate rich streams resulting in enrichment of <sup>15</sup>NO<sub>3</sub>-N if denitrification is an important process resulting in an inverse relationship between nitrate and δ <sup>15</sup>NO<sub>3</sub>-N. Conversely, if the relationship between <sup>15</sup>NO<sub>3</sub>-N and δ <sup>15</sup>N is not inversely proportional, denitrification is likely of minor importance in the reach. Variable nonlinear patterns could be indicative of <sup>15</sup>NO<sub>3</sub>-N rich input from groundwater, tributaries or concentrations in excess of microbial demand leading to massive downstream export. We measured stream <sup>15</sup>NO<sub>3</sub>-N concentrations in an urban stream receiving high nitrogen inputs from a wastewater treatment plant. Although observed NO<sub>3</sub>-N concentrations varied from 3-6 mg L<sup>-1</sup> in the stream reach, the relationship between ln NO<sub>3</sub> and δ <sup>15</sup>NO<sub>3</sub>-N was very weak, suggesting limited importance of denitrification. <br></span> DE: <span class="de"> 1615 Biogeochemical processes (4805)<br></span> DE: <span class="de"> 1803 Anthropogenic effects<br></span> DE: <span class="de"> 1806 Chemistry of fresh water<br></span> DE: <span class="de"> 1871 Surface water quality<br></span> DE: <span class="de"> 4239 Limnology<br></span> SC: <span class="sc"> North American Benthological Society [NB]<br></span> MN: <span class="mn"> 2005 Joint Assembly<br></span></p></body></html>