Pollutant Aging Studies in Soils

The bioavailability of pollutants is significantly influenced by its interactions with sedimentary organic matter. Natural organic matter (OM) is heterogeneous and exists as a multiphase macromolecular organic matrix formed from remnants of plant biobiopolymers degraded to varying degrees, dissolved and solid humic materials from plant degradation, refractory cross-linked organic matter derived from geologic processes, and deposited atmospheric combustion particles. Recent models have qualitatively described pollutant interactions with OM in soils but they often fail to adequately predict biological responses to aged contaminants. Our ability to predict pollutant behavior and bioavailability is limited by the lack of established techniques capable of probing the relevant molecular interactions of OM and our ignorance concerning the chemical composition of OM. Current models do not include chemical processes that transform plant materials to OM, nor do they include analytical methods for characterizing OM at the molecular level of detail. Thus, there is a gap in our knowledge about OM structure, maturation, and their subsequent effects on pollutant bioavailability and aging mechanisms.