Theoretical Considerations of the Partition Uptake of Nonionic Organic Compounds by Soil Organic Matter

The sorption data in aqueous systems displaya set of unique features. Most notably, as stated, the extent of soil uptake for given compounds is closely related to the organic-matter content of the soil. This chapter considers the partition equilibrium between a macromolecular organic medium and water, a system that provides a close analogy to the partition uptake by soil organic matter. It discusses the vapor uptake of some organic compounds by purified soil humic acids in comparison with uptake by soil organic matter as deduced from soil-water systems. The chapter also considers many partition characteristics of nonionic organic compounds in a solvent-water system. In keeping with the hypothesis of solute partitioning into the organic matter as the dominant mechanism of soil uptake, solutes with lower water solubilities as liquids or supercooled liquids show higher equilibrium sorption coefficients but lower limiting sorption capacities.