5 research outputs found
The contamination of commercial 15N2 gas with 15N-labeled nitrate/nitrite and ammonium and consequences for nitrogen fixation measurements
<p>The data contained herein are associated with the manuscript, "The contamination of commercial 15N2 gas stocks with 15N-labeled nitrate and ammonium and consequences for nitrogen fixation measurements", which is available at PLOS ONE.</p>
<p>We report on the presence of 15N-labeled nitrate/nitrite, ammonium, and nitrous oxide in commercial 15N2 gas and the enrichment of particulate nitrogen as a result of the biological assimilation of 15N labeled contaminants.</p
(a) δ<sup>15</sup>N<sub>NH4</sub> (log scale) of 5 µmol L<sup>−1</sup> ammonium solutions after equilibration with 0.1 mL <sup>15</sup>N<sub>2</sub> gas from respective Sigma-Aldrich and Cambridge Isotopes lecture bottles <i>vs.</i> control solutions.
<p>Sigma-Aldrich treatments utilized 40 mL ammonium solutions, whereas Cambridge Isotopes treatments utilized 100 mL ammonium solutions. (<b>b</b>) δ<sup>15</sup>N<sub>NH4</sub> of higher sensitivity equilibrations of 5 µmol L<sup>−1</sup> ammonium solutions (10 mL) with 2.0 mL <sup>15</sup>N<sub>2</sub> gas from Cambridge Isotopes lecture bottles <i>vs.</i> control solutions. n = the number of experimental replicates.</p
(<b>a</b>) δ<sup>15</sup>N<sub>NO3+NO2</sub> (log scale) of nitrate solutions (10–300 µmol L<sup>−1</sup>) following equilibration with 0.1 mL <sup>15</sup>N<sub>2</sub> gas from lecture bottles procured from three distributors.
<p>Solutions were 40 mL for Sigma-Aldrich and Campro Scientific equilibrations, and 100 mL for Cambridge Isotopes equilibrations. The solid line corresponds to the δ<sup>15</sup>N<sub>NO3</sub> of the control solutions for Sigma-Aldrich and Cambridge Isotopes experiments (δ<sup>15</sup>N<sub>NO3</sub> = 23.5±0.5‰); the dashed line corresponds to controls for Campro Scientific experiments (δ<sup>15</sup>N<sub>NO3</sub> = 14.15±0.1‰). Paired symbols identify replicate experimental treatments. (<b>b</b>) Corresponding apparent δ<sup>18</sup>O<sub>NO3+NO2</sub> of the experimental nitrate solutions. The solid line corresponds to the δ<sup>18</sup>O<sub>NO3</sub> of control solutions for the Sigma-Aldrich and Cambridge Isotope experiments (δ<sup>18</sup>O<sub>NO3</sub> = 18.9±0.3‰); the dashed line corresponds to controls for Campro Scientific experiments (25.4±0.3‰).</p
The δ<sup>15</sup>N of particulate nitrogen (δ<sup>15</sup>N<sub>PN</sub>) of <i>D. tertiolecta</i> harvested in stationary phase following growth in media containing sodium nitrate (and no ammonium) and equilibrated with <sup>15</sup>N<sub>2</sub> gas from Sigma Aldrich or Cambridge Isotopes.
<p>n = the number of experimental replicates.</p
(a) δ<sup>15</sup>N<sub>NO3+NO2</sub> (log scale) of higher sensitivity equilibrations of 10 µmol L<sup>−1</sup> nitrate solutions (10 mL) with 2 mL of <sup>15</sup>N<sub>2</sub> gas from a Cambridge Isotopes or a Sigma-Aldrich bottle.
<p>(<b>b</b>) Corresponding apparent δ<sup>18</sup>O<sub>NO3</sub> (log scale) of higher sensitivity equilibrations of the two stocks. n = the number of experimental replicates.</p