Figure 3. (a) δ¹⁵N_NH4 (log scale) of 5 µmol L⁻¹ ammonium solutions after equilibration with 0.1 mL ¹⁵N₂ gas from respective Sigma-Aldrich and Cambridge Isotopes lecture bottles vs. control solutions.

Sigma-Aldrich treatments utilized 40 mL ammonium solutions, whereas Cambridge Isotopes treatments utilized 100 mL ammonium solutions. (b) δ¹⁵N_NH4 of higher sensitivity equilibrations of 5 µmol L⁻¹ ammonium solutions (10 mL) with 2.0 mL ¹⁵N₂ gas from Cambridge Isotopes lecture bottles vs. control solutions. n = the number of experimental replicates.