Nuclear Magnetic Resonance Based Investigations of Contaminant Interactions with Soil Organic Matter

Contaminant interactions with soil organic matter (SOM) are central to understanding the fate and transport of chemicals in soil environments. Elucidation of sorption processes will facilitate the efficiency of passive remedial methods and improve the accuracy of risk assessment models. Early studies in the 1960s identified a relationship between SOM and the sorption of chemicals and laid the foundation for an area of research which is still active today. The onset of analytical instrumentation assisted the characterization of SOM chemical fractions, namely the fulvic acid (FA) and humic acid (HA) fractions. The employment of SOM chemical fractions in contaminant sorption studies has produced many empirical relationships between contaminant sorption behavior and SOM structure. More recently, molecular‐level techniques such as nuclear magnetic resonance (NMR) spectroscopy have been applied to examine specific interactions between contaminants and SOM fractions. These methods enable direct studies and are likely to further improve the fundamental understanding of contaminant interactions with SOM in the near future. For instance, NMR techniques should produce mechanistic information that will enable the accurate explanation of sorption phenomena at the macroscopic and landscape level. In addition to SOM chemical structure, researchers must consider the organic matter physical conformation at the soil–water interface because chemical methods provide structural information of the whole sample but do not provide detail about their physical architecture within the soil. This manuscript highlights studies which have examined contaminant interactions at the macroscopic‐ and molecular‐level and demonstrates the common themes stemming from different levels of investigation.