Unravelling spatiotemporal N2O dynamics in an urbanized estuary system using natural abundance isotopes
Ho, L.; Barthel, M.; Harris, S.; Vermeulen, K.; Six, J.; Bodé, S.; Boeckx, P.; Goethals, P. (2023). Unravelling spatiotemporal N2O dynamics in an urbanized estuary system using natural abundance isotopes. Wat. Res. 247: 120771. https://dx.doi.org/10.1016/j.watres.2023.120771
|  |
| Keywords |
Chemical compounds > Oxygen compounds > Oxides > Nitrogen compounds > Nitrous oxide
Cycles > Chemical cycles > Geochemical cycle > Biogeochemical cycle > Nutrient cycles > Nitrogen cycle
Brackish water |
| Author keywords |
greenhouse gas; urban river; estuary; nitrate; isotope |
| Authors | | Top |
- Ho, L., more
- Barthel, M.
- Harris, S.
- Vermeulen, K.
|
|
|
| Abstract |
Estuaries are strong sources of N2O to the atmosphere; yet we still lack insights into the impact of their biogeochemical dynamics on the emissions of this powerful greenhouse gas. Here, we investigated the spatiotemporal dynamics of the N cycle in an estuary with a focus on the emission mechanisms and pathways of N2O. By coupling N2O isotopocule analysis and substrate NO3− isotope analysis, we found that nutrient availability, oxygen level, salinity gradient and temperature variation were major drivers of the N2O emissions from the Scheldt Estuary. In winter, lower temperature and higher O2 concentration diminished denitrification rates and reduction of N2O to N2, while both were enhanced in warmer summer, causing higher fraction of reduced N2O. As a result, we found comparable N2O fluxes and dissolved concentrations between the two seasons. Decrease in salinity level and increase in NO3− concentration accelerated N2O production when moving upstream of the estuary where more urbanization and higher NO3− from wastewater discharges were found. However, these drivers had no significant effect on the fraction of N2O derived by either denitrification or nitrification and/or fungal denitrification since the fractional proportion of these pathways showed no spatiotemporal variations, remaining around 89% and 11%, respectively. These findings challenge the conventional notion that N2O fluxes are generally higher in summer because of higher denitrification rates while confirming that denitrification is the most important pathway of N2O production in the estuaries. Furthermore, our study highlight the importance of combining various isotope analyses to gain in-depth understanding about N2O emission pathways and N cycling in dynamic systems like estuaries. |
|
