Fig. 2
From: Fire-derived organic matter retains ammonia through covalent bond formation
Pyrogenic organic matter N content and H:N ratio following exposure to ammonium or ammonia. a Pyrogenic organic matter (PyOM) nitrogen (N) retention in mmol g−1 PyOM–carbon (C) measured by dry combustion is significantly associated with molar O:C ratios following exposure to NH3 and NH4+ (y = 18.25x – 0.0665, p < 0.001 and y = 3.045x − 0.008, p < 0.001, respectively). b H:N molar increases are significantly associated with O:C ratios following exposure to NH3 (y = 6.23x − 1.70, R2 = 0.59, p < 0.005, F1,10 = 14.45, RSE10 = 0.53), but not NH4+. PyOM samples retain <0.5 moles of NH3–H for every mole of NH3–N retained, compared to 2.13–23.60 moles of NH4+–H for every mole of NH4+–N retained. Green symbols represent original PyOM samples without N addition, orange symbols represent PyOM following exposure to NH4+, and blue symbols represent PyOM following exposure to NH3. Shaded bands represent the 95% confidence intervals
