Synergetic Effects of Soil Organic Matter Components During Interactions with Minerals

Area of Science:

• Soil Science
• Environmental Chemistry
• Biogeochemistry

Background:

• Mineral-associated soil organic matter (SOM) is crucial for soil carbon sequestration and climate change mitigation.
• Molecular-level understanding of mineral-SOM interactions, especially organic multilayering, is limited.
• Organic multilayering involves synergistic adsorption of organic compounds on mineral surfaces.

Purpose of the Study:

• To investigate the impact of organic multilayering on mineral-SOM interactions.
• To assess the adsorption of major SOM compounds (lauric acid, pentaglycine, trehalose, lignin) on soil minerals.
• To elucidate the molecular mechanisms governing SOM stabilization.

Main Methods:

• Integrated macroscale experiments and molecular-scale simulations.
• Assessed individual and sequential adsorption of SOM compounds on ferrihydrite, Al-hydroxide, and calcite.
• Determined adsorption affinities (Kd) and binding energies.

Main Results:

• Lauric acid exhibited significantly higher adsorption (20-40x Kd) than pentaglycine, with adsorption order: ferrihydrite > Al-hydroxide >> calcite.
• Molecular simulations revealed higher binding energy for lauric acid (30.8 kcal/mol) vs. pentaglycine (6.0 kcal/mol) on ferrihydrite, due to hydrophobicity.
• Initial adsorption of lipids/amino acids enhanced subsequent adsorption of carbohydrates/lignin via organic multilayering and particle repulsion.

Conclusions:

• Organic multilayering, driven by lipid hydrophobicity and amino acid H-bonding, significantly enhances SOM-mineral interactions.
• These molecular mechanisms are critical for understanding and improving soil carbon stabilization.
• Findings provide insights into enhancing soil organic carbon storage for climate change mitigation.