The extent to which soil hydraulics can explain ecohydrological separation

Area of Science:

• Hydrology
• Geochemistry
• Soil Science

Background:

• Field measurements show varying geochemical separation between subsurface pore waters.
• The ability of soil physics to explain isotopic differences between water types is unclear.

Purpose of the Study:

• To investigate the physical drivers of isotopic separations in soil water.
• To determine if conventional soil physics can account for observed geochemical differences.

Main Methods:

• Utilized 650 model configurations varying soil, climate, and water domain characteristics.
• Excluded confounding factors like fractionation and plant uptake.
• Simulated isotopic differences (δ²H) between mobile and immobile water domains.

Main Results:

• Coarser soils and less precipitation reduced separation between pore spaces.
• Larger immobile water domains amplified separations.
• Isotopic separations remained small (<4‰ for δ²H) across all simulations.

Conclusions:

• Conventional soil physics alone generates limited geochemical differences in pore water.
• These findings suggest soil physics is insufficient to explain large ecohydrological separations.
• Further research is needed on fractionation, artifacts, and new physiochemical mechanisms.