Inhibitory Effects of Sulfate and Nitrate Reduction on Reductive Dechlorination of PCP in a Flooded Paddy Soil

Abstract

Pentachlorophenol (PCP) is highly toxic and persistent in soils. Bioreduction of PCP often co-occurs with varying concentrations of sulfate and nitrate in flooded paddy soils where each can act as an electron acceptor. Anaerobic soil microcosms were constructed to evaluate the influence of sulfate and nitrate amendments and their redox processes. Microcosms with varying sulfate and nitrate concentrations demonstrated an inhibitory effect on reductive dechlorination of PCP compared to an untreated control. Compared to nitrate, sulfate exhibited a more significant impact on PCP dechlorination, as evidenced by a lower maximum reaction rate and a longer time to reach the maximum reaction rate. Dechlorination of PCP was initiated at the ortho-position, and then at the para- and meta-positions to form 3-CP as the final product in all microcosms. Deep sequencing of microbial communities in the microcosms revealed a strong variation in bacterial taxon among treatments. Specialized microbial groups, such as the genus of Desulfovibrio responding to the addition of sulfate, had a potential to mediate the competitive microbial dechlorination of PCP. Our results provide an insight into the competitive microbial-mediated reductive dechlorination of PCP in natural flooded soil or sediment environments.

Assembly and variation of root-associated microbiota of rice during their vegetative growth phase with and without lindane pollutant

“…Prior results have indicated that the variation of root microbiota was always age-sensitive and these microbes probably participated in the metabolic processes in roots with the growth of rice (Edwards et al, 2018;Zhang et al, 2018). For example, Haliangium had pathogen-antagonistic and plant-growth-promoting effects (Zhou et al, 2018); Desulfovibrio was representative sulfate reducing bacteria (Xu et al, 2018) and Gallionella was ironoxidizing like bacteria (Zecchin et al, 2017) (Fig. S1).…”

“…S1). Additionally, some sensitive depleted genera, like Klebsiella, Desulfitobacterium and Acinetobacter, had been reported to have a capacity for degrading or resisting di-(2-ethylhexyl) phthalate (DEHP), polyaromatic hydrocarbon (PAH) and pentachlorophenol (PCP) in paddy soils (Chen et al, 2018;Singha et al, 2018;Xu et al, 2018;Zhu et al, 2019) (Fig. S1).…”

“…dechlorinated degradation (Xu et al, 2015;Zhu et al, 2019;Feng et al, 2020a). Bachmann et al (1988) suggested that the dissipation of HCHs was mediated by some sulfatereducing bacteria and inhibited under different redox conditions in soil slurries; Xu et al (2015Xu et al ( , 2018 indicated that the dechlorination of OCP was competitively coupled with SO 4 2reduction but synergistically with Fe(III) reduction. While the soil contained these microbes, the changes induced by rice growth inhibited lindane reductive dissipation through changes to the soil chemistry.…”

“…The phyla of Proteobacteria and Firmicutes were specifically enriched in rice root endosphere (Fig. 4A and 4B), and microbes in taxa such as Burkholderia, Geobacter, Sphingomonas, Bacillus and Clostridium (genus level) were widely reported to have the potential to contribute to lindane removal (Phillips et al, 2005;Xu et al, 2018). The specific enrichment of these functional microbes may contribute to the relative lower concentration of lindane in root tissues and further be conducive to the construction of the stable endosphere microbiota.…”

In situ pilot application of nZVI embedded in activated carbon for remediation of chlorinated ethene-contaminated groundwater: effect on microbial communities

“…In general, a higher abundance of OHRB (comprising the genera Dehalobacter, Dehalococcoides and Dehalogenimonas) were found in the upper groundwater layer in CMT 1 than the lower layer in CMT 2. Low numbers of OHRB in the lower layer most likely relate to its high permeability and the high mass fluxes of oxygen and nitrate that inhibit organohalide respiration [40]. The slightly higher degree of PCE reductive degradation observed in the upper groundwater layer (Cl no.…”