Summary
This methodological study demonstrates that closed-system isotope fractionation models significantly overestimate the reduction effect on N₂O site preference values, particularly when reduction rates are high, leading to underestimation of nitrification-derived N₂O (18.7% vs 28–31%). The authors propose that a dynamic apparent net isotope effect function, which accounts for variable reduction rates across soil micropores, provides a more robust correction and substantially improves the accuracy of N₂O source partitioning in soil denitrification studies.
UK applicability
This methodological refinement is directly applicable to UK soil science research, particularly for studies quantifying agricultural N₂O emissions under diverse soil conditions. Adoption of the dynamic apparent NIE approach would improve the reliability of isotope-based source attribution in UK field studies of denitrification in arable and grassland soils.
Key measures
N₂O site preference (SP) values in ‰; N₂O and N₂ concentrations; net isotope effects (NIE) during N₂O reduction; source contribution percentages from nitrification/fungal denitrification vs bacterial denitrification
Outcomes reported
The study quantified how N₂O reduction during soil denitrification affects nitrogen isotope site preference (SP) values used to partition N₂O sources between nitrification and bacterial denitrification. Three mathematical approaches (closed-system, open-system, and dynamic apparent net isotope effect models) were compared for correcting reduction artefacts across 431 N₂O measurements from six soil incubations.
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