Attenuating Organic Contaminant Mobility by Soil Modification: Towards a Biologically Integrated Technology.

Coupling the enhanced retention of nonionic organic contaminants NOCs in quaternary ammonium QUAT-amended subsoils with bioremediation of the immobilized NOcs is being studied as a comprehensive soil restoration technology. Four areas were investigated 1 QUAT binding to soils and subsoils, 2 QUAT biocompatibility with NoC-degrading microorganisms, 3 biostability of QUATs exchanged onto natural soils and clays, and 4 NOC bioavailability to indigenous microorganisms. HDTMA-clay complexes are chemically stable when hydrophobic HDTMA bonding is limited by lowering the ionic strength and controlling companion ions. HDTMA biostability can be increased by 1 binding to clay exchange sites, 2 introduction to subsoils rather than surface soils and 3 maintaining saturated soil conditions. Although HDTMA is toxic to axenic cultures of bacteria, its toxicity is virtually eliminated by binding to clay minerals. Repopulation of the treated zone should occur once HDTNA is bound to soil.