Degradation pathways of PCB upon gamma irradiation.

Abstract

In order to understand the modifications of the chromatographic profile of Aroclor 1260 upon gamma irradiation, a total of 14 pure polychlorinated biphenyl (PCB) congeners were separately irradiated in solution. Dechlorination was observed, and the generated products were investigated by gas chromatography and mass spectrometry. Degradation proceeds more rapidly in methanol/water mixture than in petroleum ether, but the relative amount of ortho-dechlorinated congeners formed upon irradiation was smaller in the former solvent. Ortho chlorines are preferentially lost in petroleum ether except when they are involved in a 2.5 (or 3.6) substitution pattern, in which case para dechlorination becomes predominant. The precursors of some toxicologically important congeners such as congeners 77, 118, 167, and 189 have been identified. These data are useful to rationalize the modifications of the chromatographic profile of PCB complex mixture upon gamma irradiation.

Dechlorination of 3,3′,4,4′-tetrachlorobiphenyl in aqueous solution by hybrid Fe0/Fe3O4nanoparticle system

“…The reactivity of chlorines at various positions was weakened in the order as ortho-position > meta-position > para-position. [33,34] Dechlorination of PCB77 in aqueous solution by the hybrid system was in agreement with previous reports that the ortho-chlorines were lost preferentially when other positions were substituted by chlorines.…”

Degradation pathways of PCBs upon UV irradiation in hexane

“…It may be suggested that in general the reactivities of the chlorines at various positions of phenyl rings decrease in the order: ortho > meta > para, which is not in good agreement with the result of PCBs degradations upon gamma irradiation. The reactivity of chlorines at various positions upon gamma irradiation decrease in the order: ortho > para > meta [18]. In our experiments, paradechlorinations are also observed, and such a degradation pathway is barely observed upon UV irradiation of PCB containing other chlorine substituents in addition to para chlorine atoms [25].…”

Effects of ionizing radiation on pesticides in a food irradiation perspective: a bibliographic review

“…These results showed that considerable modifications of the PCB's profile occurred at this radiation dose and that the modifications are generally greater in polar solvents than in nonpolar ones. The degradation pathways of some pure model PCB congeners were investigated in aliphatic and methanolic solvents to explain these results (Lépine and Massé, 1990b).…”