SITE-ENERGY DISTRIBUTION ANALYSIS OF ORGANIC CHEMICAL SORPTION BY SOIL ORGANIC MATTER

Sorption of several hydrophobic organic compounds by selected soils, and their humic substance fractions as well, was examined using batch equilibration methods. The results could not be explained by the well known partitioning mechanism alone, but were consistent with the dual-mode sorption model for soil organic matter (SOM) in which both solid-phase dissolution and hole-filling mechanisms take place. The heterogeneous nature of the natural sorbents was demonstrated by site-energy distributions derived from the common Freundlich model. The site-energy distribution analysis is useful for examining and understanding the energetic characteristics of a sorbent. This analysis lends further support for the dual-mode model of sorption to SOM.