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Primitive electronic waste (e-waste) recycling activities release massive amounts of persistent organic pollutants (POPs) and heavy metals into surrounding soils, posing a major threat to the ecosystem and human health. Microbes capable of metabolizing POPs play important roles in POPs remediation in soils, but their phylotypes and functions remain unclear. Polychlorinated biphenyls (PCBs), one of the main pollutants in e-waste contaminated soils, have drawn increasing attention due to their high persistence, toxicity, and bioaccumulation. In the present study, we employed the culture-independent method of DNA stable-isotope probing to identify active biphenyl and PCB degraders in e-waste-contaminated soil. A total of 19 rare operational taxonomic units and three dominant bacterial genera ( Ralstonia, Cupriavidus, and uncultured bacterium DA101) were enriched in the 13 C heavy DNA fraction, confirming their functions in PCBs metabolism. Additionally, a 13.8 kb bph operon was amplified, containing a bphA gene labeled by 13 C that was concentrated in the heavy DNA fraction. The tetranucleotide signature characteristics of the bph operon suggest that it originated from Ralstonia. The bph operon may be shared by horizontal gene transfer because it contains a transposon gene and is found in various bacterial species. This study gives us a deeper understanding of PCB-degrading mechanisms and provides a potential resource for the bioremediation of PCBs-contaminated soils.

We evaluated the influence of the biodegradable chelant ethylenediamine disuccinic acid (EDDS) on plant uptake of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and Cu by corn from electronic waste (e-waste)-contaminated soil. The highest concentration and highest total uptake of Cu in corn were observed in the treatment with 5 mM EDDS, which resulted in a 4-fold increase of the Cu translocation factor (C(shoot)/C(root)) compared to the control. The concentrations of PCBs and PBDEs in shoots and roots increased with increasing application rates of EDDS, and 1.58- and 1.32-fold average increases in the concentrations of PCBs and PBDEs, respectively, were observed in shoots in the EDDS treatments. A significant positive correlation was observed between shoot Cu and shoot PCBs and PBDEs. We speculate that PCBs and PBDEs were activated by the EDDS-triggered dissolved organic carbon (DOC) and then indiscriminately taken up by roots and translocated to shoots following damage to the roots mainly by the increased extractable Cu resulting from the EDDS application.