PCB partitioning and availability in land biotreatment systems

A multi-year investigation was conducted to delineate factors affecting the aqueous phase availability and bioremediation potential of PCBs derived from oily industrial wastes in land biotreatment systems. Research was focused on the development of sampling techniques and the assessment of field and lab measures applied to equilibrium partitioning models.; A new sorbent-wick sampling device was developed to provide in situ measurements of trace quantities of PCBs in the pore water of unsaturated soils in the biotreatment beds. The hydraulic characteristics of the new samplers were evaluated through laboratory tests in unsaturated soil columns. The chemical capture and quantification potential of these devices were tested in the field and in laboratory soil column leaching experiments. The results indicate that these sampling devices are suitable for quantifying the average pore-water concentrations of chlorinated hydrophobic chemicals down to several parts per billion levels.; Equilibrium partition models were used to determine factors affecting the aqueous-phase availability of PCBs in land treatment systems. The results indicate that residual oil and grease largely controls the partitioning process. Because the oil and grease is more readily degradable, equilibrium aqueous phase concentrations of PCBs were predicted and observed to increase over the treatment period. This result has considerable implications. In general, active land biotreatment was effective in reducing di- and trichlorobiphenyls, but little reduction was seen in higher chlorinated congeners. Successive years of passive biotreatment showed little if any further reductions in PCBs.