COMPLEX THERMAL-DESORPTION OF PCBS FROM SOIL

PCBs desorb from heated soil in a complex fashion with a fast phase an d a much slower desorbing recalcitrant fraction. This recalcitrance is associated with clay layers of the montmorillonite type, the expandab le clays. The recalcitrance arises from the fraction of the PCBs bindi ng in the intercrystalline water layers of these clays. These sites pr ovide kinetic traps rather than deep energy barriers to desorption. Su ch sites may play a role in the bioavailability of the PCBs for biodeg radation or in ambient desorption and dispersal.