Effects of Ferric Oxyhydroxide on Anaerobic Microbial Dechlorination of Polychlorinated Biphenyls in Hudson and Grasse River Sediment Microcosms: Dechlorination Extent, Preferences, Ortho Removal, and Its Enhancement

Abstract

Microbial reductive dechlorination of polychlorinated biphenyls (PCBs) has been observed in many PCB-impacted sediments. However, this biodegradation is relatively site-specific and can be affected by PCB compositions and sediment geochemical conditions. To better understand the influence of a common competing electron acceptor, ferric oxyhydroxide (FeOOH), on dechlorination, two sediments (Hudson River and Grasse River sediments), and two PCB mixtures (PCB 5/12, 64/71, 105/114, and 149/153/170 in Mixture 1 and PCB 5/12, 64/71, 82/97/99, 144/170 in Mixture 2) were used for this microcosm study. The addition of 40 mmole/kg FeOOH completely inhibited PCB dechlorination in the Hudson sediment, but only moderately inhibited PCB dechlorination in the Grasse sediment with a 3-week longer lag time. The inhibitory effect in the Grasse sediment was mainly due to the loss of unflanked para dechlorination activity. Fe(II) analysis showed that dechlorination started prior to the consumption of Fe(III), which indicates PCB reduction and Fe(III) reduction were able to take place concurrently. Dehalococcoides 16S rRNA genes increased with the commencement of dechlorination in the Grasse sediment, but not in the completely inhibited Hudson sediment. Rare ortho dechlorination pathways were identified in FeOOH-amended Grasse sediment microcosms, dominated by transformations of PCB 25(24-3-CB) to PCB 13(3-4-CB) and PCB 28(24-4-CB) to PCB 15(4-4-CB). The addition of carbon sources (acetate or a fatty acid mixture with acetate, propionate, and butyrate) after 27 weeks of incubation reinitiated dechlorination in FeOOH-amended Hudson sediment microcosms. Also, the addition of carbon sources greatly enhanced ortho dechlorination in FeOOH-amended Grasse microcosms, indicating the utilization of acetate and/or the fatty acid mixture for ortho dechlorination-related microorganisms. A dechlorination pathway analysis approach revealed that para-flanked meta dechlorination was primarily preferred followed by ortho-/double-flanked meta dechlorination and single-/double-flanked para dechlorination in the Grasse sediment.

Long-Term Dechlorination of Polychlorinated Biphenyls (PCBs) in Taihu Lake Sediment Microcosms: Identification of New Pathways, PCB-Driven Shifts of Microbial Communities, and Insights into Dechlorination Potential

“…Our previous studies found that PCB71 and PCB149 could be extensively dechlorinated in Hudson and Grasse River sediments with similar levels of Dehalococcoides but with a more prevalent methane production. 54,65 It was reported that methanogens might assist dechlorination through the activity of coenzyme F430. 66 The methanogenic coenzyme F430 was demonstrated to significantly reduce the energy barrier to dechlorination.…”

Magnetic Biochar Mediates BDE-153 Accumulation and Metabolism in Rice (Oryza sativa L.) by Modulating Iron Plaque and the Fatty Acid Profile

“…The addition of Fe 3 O 4 increased the dechlorination rate by 1.5-fold, the transfer of electrons from non-dechlorinating bacteria to dechlorinating bacteria was accelerated. However, ferric iron might compete with halogenated organic pollutants for electrons, inhibiting the process of reductive dehalogenation. , Therefore, the high contents of MBC and IP might inhibit the debromination, which potentially explained why MBC at medium doses could facilitate the reductive debromination ratio on the root surfaces rather than those at high doses.…”

Integration of microbial reductive dehalogenation with persulfate activation and oxidation (Bio-RD-PAO) for complete attenuation of organohalides

“…These OHRB preferentially attack metaand/or para-chlorines in PCBs, leaving orthochlorinated PCBs as dechlorination products (Wu et al, 2002;Fennell et al, 2004;Adrian et al, 2009;Wang and He, 2013;LaRoe et al, 2014;Wang et al, 2014;Zhen et al, 2014;Wang et al, 2019). Thus far, several orthochlorine-removing microcosms have been established, e.g., o-17 culture (Cutter et al, 2001;Xu et al, 2018). However, the ortho-chlorine attacking OHRB have continued to elude enrichment and isolation.…”