[Research advances in sequestration mechanisms of hardly biodegradable organic contaminants in soil]

After entering into soil, organic contaminants often become increasingly less available to a variety of organisms and to non-vigorous extraction by organic solvents. This time-dependent reduction in availability results from the molecules sequestration by soil. Because of the sequestration, the exposure risk of hard biodegradable organic contaminants in soil may be overestimated, and the available remediation technologies are assessed incorrectly. The inherent mechanisms of the sequestration are the irreversible adsorption by clay minerals, organic matters and nonaqueous-phase liquids and the entrapment by micropores, while the key factors affecting the sequestration are the physicochemical characteristics of soil, properties of hardly biodegradable organic contaminants, and environmental conditions, e.g., moisture, temperature, pH and so on. Some critical problems in sequestration mechanisms study were pointed out, and the developing trend in this research field was prospected.