Complex thermal desorption of PCBs from soil

PCBs desorb from heated soil in a complex fashion with a fast phase and a much slower desorbing recalcitrant fraction. This recalcitrance is associated with clay layers of the montmorillonite type, the expandable clays. The recalcitrance arises from the fraction of the PCBs binding in the intercrystalline water layers of these clays. These sites provide kinetic traps rather than deep energy barriers to desorption. Such sites may play a role in the bioavailability of the PCBs for biodegradation or in ambient desorption and dispersal.