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Updated: May 29, 2026

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Published on: August 3, 2016
Nitrous oxide dynamics in a braided river system, New Zealand
T J Clough1, L E Buckthought, K L Casciotti
1Agricultural & Life Sciences Division, Lincoln Univ., New Zealand. clought@lincoln.ac.nz
River nitrous oxide (N₂O) emissions are uncertain. This study measured N₂O fluxes in a river, finding fluxes were 39-81% of IPCC estimates, suggesting current emission factors may be too low.
Area of Science:
- Environmental Science
- Geochemistry
- Climate Science
Background:
- The Intergovernmental Panel on Climate Change (IPCC) emission factor EF5-r for nitrous oxide (N₂O) from rivers was recently revised downward.
- Further reduction was limited by uncertainty in riverine N₂O dynamics and a lack of in situ measurements.
- Nitrate (NO₃-N) leaching from agricultural or sewage sources is a key input to river systems.
Purpose of the Study:
- To investigate the relationship between nitrate (NO₃-N) and nitrous oxide (N₂O-N) fluxes in a river system.
- To quantify N₂O yields and fluxes in a braided river environment.
- To assess the validity of the current IPCC emission factor (EF5-r) for riverine N₂O.
Main Methods:
- Monitoring of NO₃-N and N₂O-N concentrations at 10 sites over 397 days.
- Isotopic analysis of river water samples to trace nitrogen sources.
- Modeling of N₂O fluxes based on measured NO₃-N concentrations and N₂O saturation.
Main Results:
- Nitrate (NO₃-N) in the river originated from agricultural or sewage sources.
- Percent saturation of N₂O averaged 114%, correlating with N₂O-N concentrations.
- Modeled N₂O fluxes were strongly related to river NO₃-N concentrations (r² = 0.86).
Conclusions:
- Modeled N₂O-N fluxes were 39-81% of IPCC-derived emissions, indicating the EF5-r may not require further reduction.
- Findings do not support a further downward revision of the IPCC EF5-r.
- In situ studies are needed to confirm N₂O-N fluxes and gas transfer velocities in braided rivers.
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