Overview of partitioning and fate of contaminants: retention, retardation and regulatory requirements

Abstract

Abstract This overview study examines the principal interactions between contaminants and soil fractions responsible for contaminant partitioning, with the aim of developing a further understanding of retardation and retention processes during contaminant transport. The defining mechanisms for sorption and desorption of contaminants are generally known for many types of contaminants in interaction with specific soil fractions. However, contaminant accumulation in soil-engineered barriers or soil substrate material needs to be addressed in terms of contaminant retention or contaminant retardation as a contaminant attenuation process. This is necessary if regulatory requirements regarding natural attenuation capabilities are to be fulfilled. The combined processes leading to partitioning of contaminants in complex mixtures of contaminants and soil fractions have yet to be fully defined and understood. However, sufficient information exists concerning chemical and biologically mediated mass transfer to permit one to appreciate the need for distinguishing between irreversible sorption and temporary sorption processes. Failure to properly realize this can make the natural attenuation concept for clay barriers a ‘disaster waiting to happen’.