Polychlorinated biphenyls (PCBs) are still ubiquitous in a variety of environmental matrices, even though they were banned 30 years ago. The lighter, lesser chlorinated PCB congeners are subject to uptake and transformation by plants. It is important to study biotransformation of the parent compounds and metabolites to reveal environmental fate and effects of PCBs. Hydroxylated polychlorinated biphenyls (OH-PCBs) and PCB sulfates are well-known metabolites of PCBs. They are toxic to a variety of organisms and have raised environmental concerns. Generally, OH-PCBs are more toxic than their parent PCBs. OH-PCBs can interrupt brain function, reproductive processes and the endocrine system in mammals. OH-PCBs can be further transformed to PCB sulfates in various organisms including certain plants such as poplar. PCB sulfates have a potential activity as disruptors of endocrine signaling. Methoxylated polychlorinated biphenyls (MeO-PCBs) are metabolites of PCBs which have not been widely studied. They are likely more lipophilic and persistent than OH-PCBs. Thus, they have a potential chronic health risk and raise concern. MeO-PCBs were detected in sewage sludge of China. Information on demethylation of MeO-PCBs is quite limited. There are no reports on the transformation of MeO-PCBs to sulfate PCBs.<br/>In this study, poplar plants (<i>Populus deltoides × nigra</i>, DN34) were used as a model plant to investigate the biotransformation of MeO-PCBs in plants. Poplar cuttings (small trees) were hydroponically exposed to 4’-methoxy-4-monochlorobiphenyl (4’-MeO-PCB 3) for 10 days. After 10 days exposure, about 50% and 70% of the initial mass of 4’-MeO-PCB 3 were found in the exposure groups (plant tissues and solutions) and unplanted controls (solution samples), respectively. A hydroxylated metabolite, 4’-hydroxy-4-monochlorobiphenyl (4’-OH-PCB 3), was detected in exposure groups. The transformation ratio (yield) of 4’-OH-PCB 3 was about 2% in exposure groups. The recovered 4’-MeO-PCB 3 in the exposure groups were much lower than that of unplanted controls, indicating that other metabolism pathways existed in exposure groups besides demethylation. We expect the sulfate metabolite, 4’-PCB 3 sulfate, of 4’-MeO-PCB 3 will be detected and account for the missing mass in exposure groups. This is the first work focused on the sulfate metabolites of methoxy-PCBs in an important trophic level, plants.

Biotransformation of methoxylated polychlorinated biphenyls in whole poplar plants

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.