Dynamics of greenhouse gases in the river–groundwater interface in a gaining river stretch (Triffoy catchment, Belgium)

Jurado, Anna; Borges, Alberto V.; Pujades, Estanislao; Briers, Pierre; Nikolenko, Olha; Dassargues, Alain; Brouyère, Serge

Dynamics of greenhouse gases in the river–groundwater interface in a gaining river stretch (Triffoy catchment, Belgium) | Dynamique des gaz à effet de serre à l’interface rivière–eau souterraine dans un tronçon drainant de la rivière (bassin versant du Triffoy, Belgique) Dinámica de los gases de efecto invernadero en la interfaz río–agua subterránea en un tramo de río ganador (Cuenca Triffoy, Bélgica) (比利时Triffoy流域)一个袭夺河段中河水–地下水界面温室气体动力学 Dinâmica de gases de efeito estufa na interface rio - água subterrânea em um trecho de ganho fluvial (bacia de Triffoy, Bélgica)

2018

This study investigates the occurrence of greenhouse gases (GHGs) and the role of groundwater as an indirect pathway of GHG emissions into surface waters in a gaining stretch of the Triffoy River agricultural catchment (Belgium). To this end, nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂) concentrations, the stable isotopes of nitrate, and major ions were monitored in river and groundwater over 8 months. Results indicated that groundwater was strongly oversaturated in N₂O and CO₂ with respect to atmospheric equilibrium (50.1 vs. 0.55 μg L⁻¹ for N₂O and 14,569 vs. 400 ppm for CO₂), but only marginally for CH₄ (0.45 vs. 0.056 μg L⁻¹), suggesting that groundwater can be a source of these GHGs to the atmosphere. Nitrification seemed to be the main process for the accumulation of N₂O in groundwater. Oxic conditions prevailing in the aquifer were not prone for the accumulation of CH₄. In fact, the emissions of CH₄ from the river were one to two orders of magnitude higher than the inputs from groundwater, meaning that CH₄ emissions from the river were due to CH₄ in-situ production in riverbed or riparian zone sediments. For CO₂ and N₂O, average emissions from groundwater were 1.5 × 10⁵ kg CO₂ ha⁻¹ year⁻¹ and 207 kg N₂O ha⁻¹ year⁻¹, respectively. Groundwater is probably an important source of N₂O and CO₂ in gaining streams but when the measures are scaled at catchment scale, these fluxes are probably relatively modest. Nevertheless, their quantification would better constrain nitrogen and carbon budgets in natural systems.

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