Relationship of soil organic matter characteristics to organic contaminantsequestration and bioavailability

Sorption and desorption equilibria of phenanthrene with respect to three di fferent types of geosorbents were measured, as were the rates of desorption and biological mineralization of this representative hydrophobic organic c ontaminant. The chemical nature of the organic matter associated with each geosorbent was characterized using solid state C-13-NMR spectrometry. The r esults of these studies reveal that both the desorption behavior and the mi crobial bioavailability of the sorbed contaminant are influenced by the phy sicochemical character of the organic matter. The more reduced and condense d the organic matter, the greater the extent of sorption-desorption hystere sis, the slower the desorption rate, and the less readily bioavailable the sorbed contaminant. These observations are consistent with projections pred icated on a dual reactive domain model introduced earlier to describe the s orptive reactivities of different types of soil/sediment organic matter wit h hydrophobic organic contaminants.