Influence of pcb desorption kinetics on bioremediation and mobility risk

摘要

Historically, estimates of contaminant leaching from contaminated soil and sediment have been based on assuming equilibrium between dissolved and sorbed contaminants. Recent research has shown that equilibrium assumptions may not be valid for more hydrophobic compounds and that desorption kinetics may limit the contaminant flux from soils and sediments to the dissolved phase. For example, the desorption rate was found to limit the PCB flux from sorbed to dissolved phase for clays (Anderson, 1986; DiToro and Horzempa, 1982), sediments (Carroll et al. 1994; Gong, 1995), and diatomaceous earth (Sedlak and Andren, 1994; McLaughlin et al., 1994). Carroll et al. (1994) observed that desorption of PCBs from Hudson River sediments was a two-step process. A period of rapid desorption was complete in about 24 hours, while slow desorption step was incomplete after one year. A similar observation was reported by Witkowski et al. (1988), where Aroclor 1242 was found to desorbrapidly from sediments in the beginning, followed by a very slow rate for 6 months.