Analysis of soil organic matter at the solid-water interface by nuclear magnetic resonance spectroscopy

作者：Genest Stephanie C; Simpson Myrna J^*; Simpson Andre J; Soong Ronald; McNally David J

来源：Environmental Chemistry, 2014, 11(4): 472-482.

DOI：10.1071/EN14060

• H-1 high-resolution magic angle spinning nuclear magnetic resonance spectroscopy
• humin
• kaolinite
• montmorillonite
• organic matter preservation
• organic matter sorption
• solid-state C-13 nuclear magnetic resonance spectroscopy
• solution-state H-1 nuclear magnetic resonance spectroscopy

Organic matter (OM)-mineral interactions play an important role in OM preservation, global carbon cycling and contaminant transport. Studies have indicated that preferential sorption of OM is dependent on mineral type and solution conditions. In this study, H-1 high resolution-magic angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy was employed to examine OM chemistry in organo-clay complexes. Dissolved OM from a forest soil, Leonardite humic acid and Peat humic acid were sorbed to Ca2+ enriched kaolinite and montmorillonite. As observed using H-1 HR-MAS NMR spectroscopy, kaolinite sorbed mainly long-chain aliphatic compounds such as those from plant cuticles whereas montmorillonite sorbed a mixture of aliphatic components and proteins. These results show the preferential sorption of specific dissolved OM components on clay surfaces. This was tested further using solid-state C-13 and H-1 HR-MAS NMR analysis of whole soils containing kaolinite and montmorillonite as well as a Peat soil for contrast. The species present at the soil-water interface were mainly aliphatic components, carbohydrates and amino acids. Aromatic constituents were present in the soils (observed by solid-state C-13 NMR and by H-1 HR-MAS NMR spectroscopy when a more penetrating solvent was used) which signifies that these compounds likely exist in more hydrophobic domains that are buried and surface inaccessible. This study highlights the important role of OM interactions with clay minerals in the preservation of OM in soils and suggests that OM-OM associations may also play a role in the protection of specific OM components in soil.

• 出版日期2014