Microbial PCB degradation and binding to soil components

Interactions of polychlorinated biphenyls (PCB) with soil constituents, microbial biomass, and hydrophobic media were examined with the aim to obtain data for risk assessment of PCBs in the environment. Interactions of PCBs with dissolved organic carbon (DOC) are probably hydrophobicity-dependent in nature. There were differences between PCB interactions with swelling and non-swelling clay minerals. Non-swelling minerals were shown to play a marginal role in the environmental fate of PCB molecules. For swelling clay minerals, illite and bentonite were used as model matrices. Self-assisted formation of water-immiscible layers at specific niches of internal surfaces is suggested to facilitate the interaction of PCBs with swelling clay minerals. Pseudomonas stutzeri was found to uptake and utilize PCBs from their pure crystals and/or when sorbed to inorganic matrices or dissolved in the extracellular medium. The influence of physical processes, i.e., biosorption and evaporation, on PCB biodegradation in liquid media was quantified and used to correct observed degradation rate constants. Measured values of the 1-octanol/water partition coefficients (P) of individual PCB congeners were found to depend on the presence of other PCB congener molecules. Results from the experiments with biphenyl and 2-chlorobiphenyl (2-PCB) demonstrated that the value of P also depends on the total amount of the tested compound present in the system. The observed data were explained through the presence of monomers and dimers of biphenyl/2-PCB in the 1-octanol and the aqueous phases of the experimental system.