Short-Term Groundwater Level Fluctuations Drive Subsurface Redox Variability.

Area of Science:

• Environmental Science
• Geochemistry
• Hydrology

Background:

• Terrestrial-aquatic interfaces are dynamic zones increasingly affected by global change.
• Understanding how fluctuating water levels influence groundwater biogeochemical cycling in these areas is crucial.

Purpose of the Study:

• To investigate the spatiotemporal patterns of groundwater redox potential (Eh) at terrestrial-aquatic interfaces under fluctuating water levels.
• To determine the influence of topography and water level dynamics on redox zonation.

Main Methods:

• High-temporal resolution data collection along wetland-upland gradients.
• Measurement of groundwater redox potential (Eh) and dissolved oxygen.
• Analysis of Eh-oxygen relationships and hysteresis patterns.

Main Results:

• Topography influences groundwater Eh, with higher values in uplands than wetlands.
• Fluctuating water levels cause significant Eh variability, with occasional oxygen influxes.
• Transitional areas and wetlands showed more frequent oxidizing states than uplands.
• Distinct hysteresis patterns in the Eh-oxygen relationship indicate redox buffering capacity.

Conclusions:

• Occasional oxygen ingress at wetland-upland boundaries acts as critical biogeochemical control points.
• High-resolution monitoring is essential to capture rare but significant biogeochemical events.
• Findings support redox-informed models for predicting climate change feedback.