Relationship between nitrogen isotope ratios of NO3- and N2O in vertical porewater profiles through a polluted rain-fed peat bog
Abstract
We report a combination of delta N-15-NO3 and delta N-15-N2O values along vertical porewater profiles through a Sphagnum-dominated, high-elevation peat bog. Our objective was to distinguish between N2O production from NO3- via denitrification and N2O consumption via reduction to N-2.
Nitrate-N in runoff was isotopically heavier than NO3--N in atmospheric deposition, indicating export of organically-cycled N. Constant N2O concentrations in porewater profiles contrasted with a shift toward higher delta N-15-N2O values upward.
In the 60-30 cm depth interval, a significant negative correlation between delta N-15-NO3- and delta N-15-N2O values was observed. Higher delta N-15 values of residual NO3- in the deepest peat layer reflected higher rates of NO3- reduction.
Isotopically heavier N2O-N at shallower depths corresponded to residual N2O following partial reduction to N-2.