Synergistic Zerovalent Iron (Fe⁰) and Microbiological Trichloroethene and Perchlorate Reductions Are Determined by the Concentration and Speciation of Fe

Abstract

Trichloroethene (TCE) and perchlorate (ClO4 –) are cocontaminants at multiple Superfund sites. Fe0 is often used during TCE bioremediation with Dehalococcoides mccartyi to establish anoxic conditions in the aquifer. However, the synergy between Fe0 abiotic reactions and microbiological TCE and ClO4 – reductions is poorly understood and seldom addressed in the literature. Here, we investigated the effects of Fe0 and its oxidation product, Fe2 +, at field-relevant concentrations in promoting microbial TCE and ClO4 – reductions. Using semibatch microcosms with a Superfund site soil and groundwater, we showed that the high Fe0 concentration (16.5 g L–1) expected during Fe0 in situ injection mostly yielded TCE abiotic reduction to ethene/ethane. However, such concentrations obscured dechlorination by D. mccartyi, impeded ClO4 – reduction, and enhanced SO4 2– reduction and methanogenesis. Fe2 + at 0.25 g L–1 substantially delayed conversion of TCE to ethene when compared to no-Fe controls. A low concentration of aged-Fe0 synergistically promoted microbiological TCE dechlorination to ethene while achieving complete ClO4 – reduction. Collectively, these results illustrate scenarios relevant at or downstream of Fe0 injection zones when Fe0 is used to facilitate microbial dechlorination. Results also underscore the potential detrimental effects of Fe0 and bioaugmentation cultures coinjection for in situ treatment of chlorinated ethenes and ClO4 –.

The occurrence and ecology of microbial chain elongation of carboxylates in soils

“…Tempe and Bozeman soils were collected using a hand trowel from a depth of 0.2–0.4 m below the ground surface. Lucas soil was excavated from a depth of 1.5 m. Goodyear soil was acquired through drill coring from a depth of 25–52 m below ground surface [ 27 ]. Equal parts of ~0.1 kg of soil cores from 25–52 m depths were homogenized to create composite Goodyear soil.…”

An Ion Chromatography Method for Simultaneous Quantification of Chromate, Arsenate, Selenate, Perchlorate, and Other Inorganic Anions in Environmental Media

“…Three groundwater samples were obtained for testing. One groundwater sample was from Phoenix Goodyear Airport-North Superfund site (AZ) (Rangan et al , 2020 ). The other samples were collected from two confidential sites in the Southwestern United States.…”

“…The developed IC method was applied to monitor anions in soil and culture-only batch microcosms. Soil laboratory microcosms (Ziv-El et al , 2011 ; Rangan et al , 2020 ; Joshi et al , 2021 ) focused on abiotic and microbiological Cr (VI) reduction were established in 160 mL glass serum bottles with 25 g of Cr (VI)-contaminated soil and 100 mL anaerobic mineral medium as described elsewhere (Delgado et al , 2012 , 2017 ). The soil was collected from 0 to 0.25 m depth at the TCCL site, India, and was homogenized in the anaerobic glove chamber (Coy Laboratory Products, Inc., Grass Lake, MI) under 3.5% H 2 and 96.5% N 2 atmosphere.…”

“…3 ) in drinking water, industrial wastewater, surface waters, groundwater, acid mine drainage, soils, and sediments (Riley, 1992;Gandhi et al, 2002). In groundwater, acid mine drainage and other process waters, Cr (VI) is often a co-contaminant with other regulated anions such as arsenate ion (AsO 3 À 4 ) and selenate ion (SeO 2 À 4 ) (referred henceforth as As (V) and Se (VI), respectively) or perchlorate ion (ClO À 4 ) (Pyrzyńska, 2002;Urbansky, 2002;Parker et al, 2008;Yoon et al, 2009;Zhitkovich, 2011;Wang et al, 2013;Steinmaus, 2016;Khamkhash et al, 2017;WHO, 2018).…”

In situ nanoremediation of soils and groundwaters from the nanoparticle's standpoint: A review

“…Such insight is crucial to understand the potential synergy between nano-and bioremediation by determining, for example, if nZVI may have a biostimulatory effect on microorganisms participating in bioremediation. High Fe 0 concentrations (16.5 g/L) were deposited in both a sampled soil and groundwater contaminated by TCE and ClO4 -, preliminarily bioaugmented with dechlorinating microorganisms (Rangan et al, 2020). It was observed that the particles promoted TCE abiotic reduction to ethene and ethane, while impairing microbiological TCE and ClO4reduction.…”