Sequestration of organic contaminants in soil/sediment and its impact on contaminant fate

Adsorption and desorption are critical processes controlling the fate and transport of organic contaminants in natural environment. Numerous studies have shown that only a fraction of contaminants in soil or sediment can readily be desorbed to the aqueous phase, while desorption of the remaining fraction is very difficult and does not follow the conventional desorption models-a phenomenon typically referred to as ＂resistant desorption＂ or ＂sequestration＂ and is argued by many as the cause of reduced availability of contaminants in soil and sediment. While this reduced availability often reduces the effectiveness of soil and sediment remediation, the same effect can also greatly reduce risk of contaminated soil and sediment. The authors have conducted extensive lab and field studies to characterize the unique properties of sequestration of organic contaminants and to understand the mechanism（s） controlling sequestration. Thus far, over 50 different contaminant-soil/sediment combinations have been evaluated, using contaminants of varied physical-chemical properties （e.g., chlorinated benzenes, PAHs, PCBs, DDT, atrazine, hexachlorocyclohexane isomers, etc.）. Several unique characteristics of sequestration have been observed, and the most striking one is that despite the significant differences in chemical and soil properties, desorption of sequestered contaminants for all the contaminant-soil/sediment combinations exhibited very similar KOC （organic-carbon normalized partition coefficient） and very similar desorption kinetics.

Sequestration of organic contaminants in soil/sediment and its impact on contaminant fate