Published in Hydrogeology Journal, this research explores how fluctuations in the water table influence nitrogen dynamics in Mediterranean riparian aquifers, a key process for understanding groundwater quality, nutrient transport and stream ecosystem functioning.

The study uses a 1-metre experimental soil column filled with riparian soil from Font del Regàs, Spain, to reproduce water table fluctuations under controlled conditions. Over 16 days, the researchers monitored hydrological and chemical changes using pressure, moisture and redox sensors, while analysing dissolved inorganic nitrogen, dissolved organic carbon and microbial communities.

Unlike studies based on homogeneous porous media, this work provides insights from a more natural soil profile, helping to better understand how Mediterranean riparian zones behave during wetting and drying cycles.

📈 Key insights from the paper:

🔹 Water table fluctuations play a critical role in controlling nitrogen transformation and mobilization in shallow riparian aquifers.
🔹 The upper riparian soils promoted aerobic conditions, allowing ammonium oxidation and nitrate accumulation in the variably saturated zone.
🔹 During water table rise, nitrate was rapidly consumed under oxygen-limited saturated conditions, especially in the presence of dissolved organic carbon.
🔹 When the water table fell, dissolved organic carbon moved downward, promoting denitrification processes in deeper soil layers.
🔹 Surface flooding generated pulses of nitrate and dissolved organic carbon to groundwater, helping explain post-storm increases observed in headwater streams.
🔹 The findings highlight the importance of considering groundwater level fluctuations to better understand nutrient cycling in Mediterranean catchments under changing climatic conditions.

This work contributes to advancing knowledge on groundwater–surface water interactions, nitrogen cycling and water quality management in Mediterranean riparian systems.

This research was supported by the National Science Foundation, MCIN/AEI and FEDER “Una manera de hacer Europa”, as well as the ConMimo project and the ERASMUS+ Internship Program.