Transformation and environmental fate of 6-OH-BDE-47 and 6-MeO-BDE-47 in oxic and anoxic sediments.

Pollutants often exhibit different environmental behaviors at varying redox potentials, and the fate and microbial response of 6-OH-BDE-47 and 6-MeO-BDE-47 under these conditions remain unclear. Herein, ¹⁴ C-labeled 6-OH-BDE-47 and 6-MeO-BDE-47 were used to investigate their fate in water-sediment systems at different redox potentials. For 6-OH-BDE-47, aerobic microorganisms and nitrate electron acceptors promoted nonextractable residues (NERs) formation and anaerobic microorganisms facilitated their release and was highest formed in the O ₂ -containing group. For 6-MeO-BDE-47, aerobic microorganisms, electron acceptors, and anaerobic microorganisms promoted NER formation, and was highest formed in the nitrate group. Microorganisms markedly promoted 6-OH/MeO-BDE-47 transformation. For 6-OH-BDE-47, the degradation followed the order nitrate group (29.6 %) > O ₂ -containing group (6.5 %) > sulfate group (1.45 %) > anaerobic group (0 %), while for 6-MeO-BDE-47, the order was O ₂ -containing group (8.8 %) > nitrate group = sulfate group = anaerobic group (0 %). The complexity of the 6-OH-BDE-47 and 6-MeO-BDE-47 microbial community network was consistent with the results of redox potentials, where microbial networks connectivity linking were more complex under O ₂ -containing and nitrate conditions. Overall, our study comprehensively revealed the fate of 6-OH-BDE-47 and 6-MeO-BDE-47 under different redox conditions, showing that electron acceptors can alter microbial community structure and regulating interactions. It provided guidelines for selecting electron acceptors in the remediation of 6-OH-BDE-47 and 6-MeO-BDE-47.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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