Physical factors negatively affecting evaluation of long-term biodegradation experiments of polychlorinated biphenyls

Critical factors in chemical characterization for the evaluation of decontamination in solids using advanced oxidation

Advanced oxidation technologies (AOT) have been applied to the treatment of numerous organic pollutants embedded in solid matrices (e.g., soil, sediments, sludge, etc.). Given potentially strong matrix-analyte interactions in solids, chemical characterization of both the target contaminants and their oxidation products is critical for the evaluation of any decontamination method. The success of AOT applications has been evaluated either directly (based on the removal of original contaminants, extent of mineralization, and/or formation of by-products), or indirectly, e.g., based on toxicity or chemical oxygen demand. Since indirect methods do not provide comprehensive understanding of the pollutants' fate, direct analytical approaches are covered in this review while focusing on sample preparation and detailed chromatographic characterization, assessing the strengths and weaknesses of these methods. The significance of sample preparation, in particular extraction, is discussed with respect to the nature of matrix-analyte interactions, as those may also affect the selection of the remediation method. The ultimate goal of this review is the presentation of methods employed to achieve mass balance closure, which is essential to ensure the full understanding of degradation pathways.

Degradation of polychlorinated biphenyl mixtures by the lignin-degrading fungus Phanerochaete chrysosporium

Degradation of lower-chlorinated and higher-chlorinated PCB congeners (Delor 103 and Delor 105 as equivalents of Aroclor 1242 and Aroclor 1254, respectively) by the white-rot fungus Phanerochoete chrysosporium was investigated in N-limited and non-limited media. No degradation of either Delor 103 or Delor 105 was found in a N-limited medium 9 d after their addition whereas in the non-limited medium during the same period their levels dropped by 55 and 58%, respectively. The degradation was non-specific and no significant differences in the degradation of di-, tri-, tetra-, penta-, hexa-, and hepta-congeners were found. No activity of Mn-dependent peroxidase (MnP) or lignin peroxidase (LiP) was detectable in the non-limited medium. We assume that the degradation of PCBs by P. chrysosporium is relatively non-specific, takes place under non-limited conditions and is independent of the activities of MnP or LiP.

Investigation into PCB biodegradation using uniformly 14C-labelled dichlorobiphenyl

Biodegradation of polychlorinated biphenyls (PCBs) in soil is considered to be very complex due to various physico-chemical factors involved. Isotope labelling technique is the best to trace fate of the xenobiotic in the environment. In this work, the uniformly 14C-labelled PCB congener 11 (3,3'-chlorobiphenyl) was chosen as a low chlorinated coplanar biphenyl which was assumed to be readily degraded by microorganisms. Pleurotus ostreatus and two Pseudomonas species, representing white rot fungi and soil bacteria were used separately or in a consortium. The amount of liberated 14CO2 and radio-HPLC, HPLC, GC-MS, and radio-TLC analyses of extracts at the end of a two-month experiment showed that the mineralization of PCB 11 was < 0.4%, volatilization < 3.1%, and 30% of radioactivity was irreversibly bound to the soil matrix. The respective contents of all intermediate metabolites were 4.7 to 10.5 and 2.5 to 2.7% where Pseudomonas alcaligenes alone or in combination with P. putida was applied. 3-Chlorobenzoic acid was the major biodegradation product.

Removal of PCBs by various white rot fungi in liquid cultures

The ability of Phanerochaete chrysosporium, Trametes versicolor, Coriolopsis polyzona, and Pleurotus ostreatus growing in a mitogen-limited mineral medium (NMM) to degrade PCBs in a commercial, Delor 106 mixture at a concentration of 0.9 ppm was compared. The respective amount of PCBs removed from the fungal cultures within 3 weeks were 25, 50, 41 and 0%. The capacities of the individual fungal species to remove PCBs correlated to some extent with their capabilities of decolorization of NMM agar containing both Poly R-478 or Remazol Brilliant Blue R dyes. Enzyme estimations indicated that both high and relatively stable activities of Mn-dependent peroxidase, Mn-independent peroxidase, lignin peroxidase, and laccase characterized efficient PCB degraders.