Investigating Soil Organic Matter Complexation in Natural Analog Systems Using Geoelectrical Methods

Area of Science:

• Geochemistry
• Environmental Science
• Geophysics

Background:

• Soil organic matter (SOM) interactions with minerals are crucial for soil health, carbon sequestration, and nutrient cycling.
• Understanding these interactions is key to managing soil ecosystems effectively.
• Ferrihydrite and SOM components like pentaglycine are common in soils, influencing these processes.

Purpose of the Study:

• To investigate the sensitivity of geoelectrical methods, specifically induced polarization (IP), to organo-mineral complex formation.
• To assess the potential of IP as a noninvasive tool for monitoring mineral-fluid interactions in soils.
• To understand the dynamics of SOM adsorption onto mineral surfaces.

Main Methods:

• Multiscale experiments were conducted using millifluidic and column systems.
• Ferrihydrite-coated materials (sand, ceramic beads, PDMS) were used to simulate soil conditions.
• Induced polarization (IP) measurements and scanning electron microscopy (SEM) were employed.

Main Results:

• A significant increase in imaginary conductivity (IP parameter) was observed after pentaglycine injection, indicating surface complexation.
• Subsequent decreases in imaginary conductivity suggested surface saturation or reduced adsorption.
• SEM imaging confirmed morphological changes on ferrihydrite surfaces, supporting IP data.
• Consistent IP responses across different experimental setups validated measurement reproducibility.

Conclusions:

• Geoelectrical methods, particularly IP, show high sensitivity to organo-mineral complex formation.
• IP can serve as a noninvasive technique for real-time monitoring of mineral-fluid interfaces and SOM dynamics.
• These findings highlight the potential for applying IP in soil science and environmental monitoring.