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Updated: May 14, 2026

The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations
Published on: August 3, 2016
Diurnal pattern in nitrous oxide emissions from a sewage-enriched river
Yongqiu Xia1, Yuefei Li, Xiaobo Li
1State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. yqxia@issas.ac.cn
Diurnal variations in nutrient transformation and dissolved oxygen (DO) can impact nitrous oxide (N2O) emission estimates. Hourly measurements revealed no significant diurnal patterns in N2O flux, but daytime emissions were higher than nighttime.
Area of Science:
- Environmental Science
- Water Chemistry
- Atmospheric Chemistry
Background:
- Nitrous oxide (N2O) emissions from rivers are a significant environmental concern.
- Inaccurate N2O emission estimates can result from diurnal variations in nutrient cycling and dissolved oxygen (DO).
- Sewage-enriched rivers present unique challenges for accurately quantifying N2O fluxes.
Purpose of the Study:
- To investigate the diurnal patterns of N2O fluxes and dissolved N2O concentrations in a sewage-enriched river.
- To identify key environmental factors controlling N2O emissions in this aquatic system.
- To determine optimal sampling times for representative N2O flux measurements.
Main Methods:
- Hourly measurements of N2O fluxes, dissolved N2O concentrations, and controlling variables (pH, DO, nutrients, temperature) over 3-day and night cycles.
- Sampling conducted at five sites along a sewage-enriched river in the Taihu region.
- Statistical analysis to assess diurnal patterns and identify controlling factors.
Main Results:
- No significant diurnal patterns were observed in overall N2O emissions or dissolved N2O saturation.
- Mean N2O emissions and dissolved N2O saturation were significantly higher during the day compared to the night.
- Key factors controlling N2O flux included pH, DO, ammonium (NH4+), sulfate (SO42-), and air and water temperatures.
- Sampling at 19:00h was found to be representative of the daily average N2O flux.
Conclusions:
- Diurnal variations in nutrient transformation and DO do not necessarily lead to significant diurnal patterns in N2O flux in sewage-enriched rivers.
- Daytime conditions favor higher N2O emissions compared to nighttime.
- A single sampling event at 19:00h can provide a reliable estimate of the daily average N2O flux in such environments, simplifying monitoring efforts.
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