N₂O emissions fueled by eutrophication in a shallow lake

Area of Science:

• Environmental Science
• Limnology
• Atmospheric Chemistry

Background:

• Lakes are significant sources of nitrous oxide (N₂O), a potent greenhouse gas.
• The impact of eutrophication on lake N₂O emissions is not well understood.
• Accurate quantification of N₂O emissions is crucial for climate change mitigation.

Purpose of the Study:

• To investigate the spatiotemporal variations of N₂O concentrations, fluxes, and indirect emission factors (EF_5r) in a shallow eutrophic lake.
• To identify the drivers of N₂O emissions, particularly the role of eutrophication.
• To compare estimated emission factors with Intergovernmental Panel on Climate Change (IPCC) default values.

Main Methods:

• Field measurements of N₂O concentrations in water and diffusive fluxes over 2019-2020.
• Calculation of indirect emission factors (EF_5r).
• Statistical analysis to correlate N₂O dynamics with trophic status and nutrient concentrations.

Main Results:

• Ulansuhai lake is a persistent source of atmospheric N₂O, with mean concentrations of 20.0 ± 6.7 nmol/L and fluxes of 16.50 ± 21.52 µmol/(m²·day).
• Estimated indirect emission factors (EF_5r) were higher (0.0037 ± 0.0060) than IPCC default values (0.0026).
• N₂O emissions showed significant seasonal variation and were positively correlated with lake trophic status and nutrient levels.

Conclusions:

• Eutrophication plays a critical role in enhancing N₂O emissions from lakes.
• The findings suggest that current IPCC emission inventories may underestimate N₂O emissions from eutrophic lakes.
• Management strategies to reduce lake eutrophication are essential for mitigating N₂O emissions.