Papers by Edward J O'Loughlin
Minerals, 2022
Chlorinated ethenes have been used extensively as solvents, degreasers, and dry-cleaning agents i... more Chlorinated ethenes have been used extensively as solvents, degreasers, and dry-cleaning agents in a range of commercial and industrial applications. This has created a legacy of contaminated soils and groundwater, particularly with respect to perchloroethylene (PCE; a.k.a. tetrachloroethene—C2Cl4), and trichloroethylene (TCE; a.k.a. trichloroethene—C2HCl3), prompting the development of a wide array of treatment technologies for remediation of chlorinated ethene-contaminated environments. Green rusts are highly redox-active layered Fe(II)-Fe(III) hydroxides that have been shown to be facile reductants for a wide range of organic and inorganic pollutants. The reduction of chlorinated ethenes [vinyl chloride (VC); 1,1-dichloroethene(11DCE), cis-1,2-dichloroethene (c12DCE), trans-1,2-dichloroethene (t12DCE), TCE, and PCE] was examined in aqueous suspensions of green rust, alone as well as with the addition of Ag(I) (AgGR) or Cu(II) (CuGR). Green rust alone was ineffective as a reductan...
U(VI) Reduction by Biotic and Abiotic Green Rusts S. YAN*, M. I. BOYANOV, B. MISHRA, K. M. KEMNER... more U(VI) Reduction by Biotic and Abiotic Green Rusts S. YAN*, M. I. BOYANOV, B. MISHRA, K. M. KEMNER, E. J. O'LOUGHLIN School of Earth Sciences, China University of Geosciences, Wuhan, China (*correspondence: [email protected]) Biosciences Division, Argonne National Laboratory, Argonne, IL, USA ([email protected], [email protected], [email protected]) Bulgarian Academy of Sciences, Institute of Chemical Engineering, Sofia, Bulgaria ([email protected])
Goldschmidt Abstracts, 2020
Biogeochemistry, 2004
Both dissolved organic carbon (DOC) and iron play an important role in biogeochemical processes i... more Both dissolved organic carbon (DOC) and iron play an important role in biogeochemical processes in lacustrine benthic environments. Moreover, recent evidence has shown that both substances can act as active reductants in the redox transformation of organic pollutants. This paper examines the nature and abundance of DOC and dissolved ferrous iron (Fe II) in porewaters from a sediment core collected in Green Bay, WI, USA. The concentration of dissolved Fe II and the abundance, absorbance at 280 nm (A 280 nm), molar absorptivities (e 280 nm), molecular weights, and polydispersities of DOC were measured as a function of depth in porewaters. Dissolved Fe II concentrations increased from 3.6 lM near the sediment-water interface to 163 lM at a depth of 11 cm, then gradually declined. The DOC distribution varied with sediment depth, with the greatest variation in porewater DOC content and properties occurring in the transitional zone between oxic and suboxic conditions. The down-core porewater DOC profile was characterized by an increase in DOC concentration with depth from 0.64 mM OC at 1 cm to 1.23 mM OC at 13 cm, below which it remained relatively constant. A strong correlation was observed between Fe II and DOC concentrations, suggesting that these constituents co-accumulate in these porewaters. The correlation between the DOC concentration of the porewaters and A 280 nm was significant, making this parameter a good predictor for DOC concentrations in these waters. The molecular weight distributions of the porewater DOC were primarily monomodal, with relatively low polydispersivities. Weight-average molecular weights ranged from 1505 to 1949 Da. This data set is unique in that it is the first detailed study of a relatively highly resolved DOC profile of benthic porewater in surficial sediment from the Laurentian Great Lakes.
The reductive dechlorination of carbon tetrachloride (CT) was examined in aqueous suspensions of ... more The reductive dechlorination of carbon tetrachloride (CT) was examined in aqueous suspensions of sulfate green rust (GRSO4) amended with either Co(II), Cr(VI), Hg(II), Mn(II), Mo(VI), Ni(II), Pb(II), V(III), or Zn(II). The rate of CT reduction in the Hg(II)-amended GRSO4 suspension was ~1000 times faster than in unamended GRSO4. CT reduction was moderately enhanced in the Cr(III) , Mn(II)-, Mo(VI)-, Pb(II)-, and V(III)-amended systems. No increase in the rate of CT reduction was observed in the Co(II)-, Ni(II)-, or Zn(II)-amended systems. Chloroform (CF) was the major product of CT reduction, with minor amounts of methane and traces of ethene, and ethane; dichloromethane and chloromethane were not observed. A reaction pathway scheme is proposed in which CT is reduced primarily to chloroform (CF) and minor non-chlorinated end products, largely through a series of one-electron reductions forming radicals and carbenes/carbenoids.
Minerals, 2021
The bioreduction of Fe(III) oxides by dissimilatory iron-reducing bacteria may result in the form... more The bioreduction of Fe(III) oxides by dissimilatory iron-reducing bacteria may result in the formation of a suite of Fe(II)-bearing secondary minerals, including magnetite (a mixed Fe(II)/Fe(III) oxide), siderite (Fe(II) carbonate), vivianite (Fe(II) phosphate), chukanovite (ferrous hydroxy carbonate), and green rusts (mixed Fe(II)/Fe(III) hydroxides). In an effort to better understand the factors controlling the formation of specific Fe(II)-bearing secondary minerals, we examined the effects of Fe(III) oxide mineralogy, phosphate concentration, and the availability of an electron shuttle (9,10-anthraquinone-2,6-disulfonate, AQDS) on the bioreduction of a series of Fe(III) oxides (akaganeite, feroxyhyte, ferric green rust, ferrihydrite, goethite, hematite, and lepidocrocite) by Shewanella putrefaciens CN32, and the resulting formation of secondary minerals, as determined by X-ray diffraction, Mössbauer spectroscopy, and scanning electron microscopy. The overall extent of Fe(II) prod...
PLOS ONE, 2021
Iron reduction and sulfate reduction are two of the major biogeochemical processes that occur in ... more Iron reduction and sulfate reduction are two of the major biogeochemical processes that occur in anoxic sediments. Microbes that catalyze these reactions are therefore some of the most abundant organisms in the subsurface, and some of the most important. Due to the variety of mechanisms that microbes employ to derive energy from these reactions, including the use of soluble electron shuttles, the dynamics between iron- and sulfate-reducing populations under changing biogeochemical conditions still elude complete characterization. Here, we amended experimental bioreactors comprised of freshwater aquifer sediment with ferric iron, sulfate, acetate, and the model electron shuttle AQDS (9,10-anthraquinone-2,6-disulfonate) and monitored both the changing redox conditions as well as changes in the microbial community over time. The addition of the electron shuttle AQDS did increase the initial rate of FeIII reduction; however, it had little effect on the composition of the microbial commu...
Journal of Environmental Management, 2021
The construction of an underground facility can dramatically change the quality, flow direction, ... more The construction of an underground facility can dramatically change the quality, flow direction, and level of groundwater. It may also impact subsurface microbial composition and activity. Groundwater quality was monitored over eight years in two observational wells near an underground disposal facility on the east coast of South Korea. The results showed dramatic increases in dissolved ions such as O2, Na, Ca, Mg, and SO4 during facility construction. Seepage water samples downgradient from the silos and tunnels, and precipitates deposited along the seepage water flow path were collected to determine the impact inside the disposal facility. X-ray analysis (powder X-ray diffraction (pXRD) and X-ray absorption fine structure (XAFS)) were used to characterize the mineral precipitates. Microbial community composition was determined by 16S rRNA gene sequencing. The seepage water composition was of two types: Ca-Cl and Ca-Na-HCO3. The ratio of Cl and δ18O showed that the Ca-Cl type seepage water was influenced by groundwater mixed with seawater ranging from 2.7% to 15.1%. Various sulfate-reducing bacteria were identified in the Ca-Cl type seepage water, exhibiting relatively high sulfate content from seawater intrusion. Samples from the Ca-Na-HCO3 type seepage water had an extremely high pH (>10) and abundance of Hydrogenophaga. The precipitates observed along the flow path of the seepage water included calcite, ferrihydrite, green rust, and siderite, depending on seepage water chemistry and microbial activity. This study suggests that the construction of underground structures creates distinct, localized geochemical conditions (e.g., high alkalinity, high salinity, and oxic conditions), which may impact microbial communities. These biogeochemical changes may have undesirable large-scale impacts such as water pump clogging. An understanding of the process and long-term monitoring are essential to assess the safety of underground facilities.
Journal of Environmental Management, 2021
Urban subsurface environments are often different from undisturbed subsurface environments due to... more Urban subsurface environments are often different from undisturbed subsurface environments due to the impacts of human activities. For example, deterioration of underground infrastructure can introduce elevated levels of Ca, Fe, and heavy metals into subsurface soils and groundwater. Likewise, leakage from sewer systems can lead to contamination by organic C, N, S, and P. However, the impact of these organic and inorganic compounds on biogeochemical processes including microbial redox reactions, mineral transformations, and microbial community transitions in urban subsurface environments is poorly understood. Here we conducted a microcosm experiment with soil samples from an urban construction site to investigate the possible biotic and abiotic processes impacted when sulfate and acetate or lactate were introduced into an urban subsurface environment. In the top-layer soil (0-0.3 m) microcosms, which were highly alkaline (pH > 10), the major impact was on abiotic processes such as secondary mineral precipitation. In the mid-layer (2-3 m) soil microcosms, the rate of Fe(III)-reduction and the amount of Fe(II) produced were greatly impacted by the specific organic acid added, and sulfate-reduction was not observed until after Fe(III)-reduction was complete. Near the end of the incubation, some genera related to syntrophic acetate oxidation and methanogenesis were observed in the lactate-amended microcosms. In the bottom-layer (7-8 m) soil microcosms, the rate of Fe(III)-reduction and the amount of Fe(II) produced were affected by the concentration of amended sulfate. Sulfate-reduction was concurrent with Fe(III)-reduction, suggesting that Fe(II) production was likely due to abiotic reduction of Fe(III) by sulfide produced by microbial sulfate reduction. The slightly acidic initial pH (~5.8) of the mid-soil system was a major factor controlling sequential microbial Fe(III) and sulfate reduction versus parallel Fe(III) and sulfate reduction in the bottom soil system, which had a neutral initial pH (~7.2). 16S rRNA gene-based community analysis revealed a variety of indigenous microbial groups including alkaliphiles, dissimilatory iron and sulfate reducers, syntrophes, and methanogens tightly coupled with, and impacted by, these complex abiotic and biogeochemical processes occurring in urban subsurface environments.
Journal of Hazardous Materials, 2021
Although several studies have investigated the effects of Sb contamination on surrounding environ... more Although several studies have investigated the effects of Sb contamination on surrounding environments and indigenous microorganisms, little is known about the effect of co-contamination of Sb and toxic metal(loid)s. In this study, the occurrence of Sb and other toxic metal(loid)s near an operating Sb refinery and near-field landfill site were investigated. Topsoil samples near the refinery had high Sb levels (∼3250 mg kg-1) but relatively low concentrations of other toxic metal(loid)s. However, several soil samples taken at greater depth from the near-field landfill site contained high concentrations of As and Pb, as well as extremely high Sb contents (∼21,400 mg kg-1). X-ray absorption fine structure analysis showed that Sb in the soils from both sites was present as Sb(V) in the form of tripuhyite (FeSbO4), a stable mineral. Three-dimensional principal coordinate analysis showed that microbial community compositions in samples with high toxic metal(loid)s concentrations were significantly different from other samples and had lower microbial populations (∼104 MPN g-1). Sequential extraction results revealed that Sb is present primarily in the stable residual fraction (∼99 %), suggesting low Sb bioavailability. However, microbial redundancy analysis suggested that the more easily extractable Pb might be the major factor controlling microbial community compositions at the site.
Heliyon, 2021
Increasing use and mining of antimony (Sb) has resulted in greater concern involving its fate and... more Increasing use and mining of antimony (Sb) has resulted in greater concern involving its fate and transport in the environment. Antimony(V) and (III) are the two most environmentally relevant oxidation states, but little is known about the redox transitions between the two in natural systems. To better understand the behavior of antimony in anoxic environments, the redox transformations of Sb(V) were studied in biotic and abiotic reactors. The biotic reactors contained Sb(V) (2 mM as KSb(OH) 6), ferrihydrite (50 mM Fe(III)), sulfate (10 mM), and lactate (10 mM), that were inoculated with sediment from a wetland. In the abiotic reactors, The interaction of Sb(V) with green rust, magnetite, siderite, vivianite or mackinawite was examined under abiotic conditions. Changes in the concentrations of Sb, Fe(II), sulfate, and lactate, as well as the microbial community composition were monitored over time. Lactate was rapidly fermented to acetate and propionate in the bioreactors, with the latter serving as the primary electron donor for dissimilatory sulfate reduction (DSR). The reduction of ferrihydrite was primarily abiotic, being driven by biogenic sulfide. Sb and Fe K-edge X-ray absorption near edge structure (XANES) analysis showed reduction of Sb(V) to Sb(III) within 4 weeks, concurrent with DSR and the formation of FeS. Sb K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy analysis indicated that the reduced phase was a mixture of Sand O-coordinated Sb(III). Reduction of Sb(V) was not observed in the presence of magnetite, siderite, or green rust, and limited reduction occurred with vivianite. However, reduction of Sb(V) to amorphous Sb(III) sulfide occurred with mackinawite. These results are consistent with abiotic reduction of Sb(V) by biogenic sulfide and reveal a substantial influence of Fe oxides on the speciation of Sb(III), which illustrates the tight coupling of Sb speciation with the biogeochemical cycling of S and Fe.
Environmental Science & Technology, 2021
Reduction of U(VI) to U(IV) drastically reduces its solubility and has been proposed as a method ... more Reduction of U(VI) to U(IV) drastically reduces its solubility and has been proposed as a method for remediation of uranium contamination. However, much is still unknown about the kinetics, mechanisms, and products of U(VI) bioreduction in complex systems. In this study, U(VI) bioreduction experiments were conducted with Shewanella putrefaciens strain CN32 in the presence of clay minerals and two organic ligands: citrate and EDTA. In reactors with U and Fe(III)-clay minerals, the rate of U(VI) bioreduction was enhanced due to the presence of ligands, likely because soluble Fe3+- and Fe2+-ligand complexes served as electron shuttles. In the presence of citrate, bioreduced U(IV) formed a soluble U(IV)-citrate complex in experiments with either Fe-rich or Fe-poor clay mineral. In the presence of EDTA, U(IV) occurred as a soluble U(IV)-EDTA complex in Fe-poor montmorillonite experiments. However, U(IV) remained associated with the solid phase in Fe-rich nontronite experiments through the formation of a ternary U(IV)-EDTA-surface complex, as suggested by the EXAFS analysis. Our study indicates that organic ligands and Fe(III)-bearing clays can significantly affect the microbial reduction of U(VI) and the stability of the resulting U(IV) phase.
Microbiology Resource Announcements, 2020
Here, we report the draft genome sequence of Arthrobacter sp. strain ATCC 49987, consisting of th... more Here, we report the draft genome sequence of Arthrobacter sp. strain ATCC 49987, consisting of three contigs with a total length of 4.4 Mbp. Based on the genome sequence, we suggest reclassification of Arthrobacter sp. strain ATCC 49987 as Pseudarthrobacter sp. strain ATCC 49987.
Environmental Science & Technology Letters, 2014
Acid extraction followed by a colorimetric assay is a widely used approach for the determination ... more Acid extraction followed by a colorimetric assay is a widely used approach for the determination of the total Fe(II) in samples from suboxic and anoxic environments. Under sulfidogenic conditions, these samples can contain both metal sulfides and iron (hydr)oxides. Our comparisons between 0.5 N HCl extraction and X-ray absorption fine structure (XAFS) analysis of systems containing 40 mM Fe(III) as specific (hydr)oxides and 10 mM FeS showed that the presence of sulfide can result in significant overestimation of the total Fe(II) by acid extraction. The total Fe(II) determined by XAFS was consistent with the added FeS. However, the total Fe(II) determined by extraction was significantly higher and dependent on the nature of the Fe(III) (hydr)oxides; the rates and extent of Fe(II) production were higher with ferrihydrite and lepidocrocite than with goethite. Total Fe(II) concentrations determined following acid extraction might be overestimated when iron (hydr)oxides and sulfide minerals are present in samples.
Microscopy and Microanalysis, 2006
Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois,... more Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006
Environmental Science & Technology, 2010
Biogenic Fe II phases (magnetite, green rust, siderite, vivianite, etc.) provide a reservoir of r... more Biogenic Fe II phases (magnetite, green rust, siderite, vivianite, etc.) provide a reservoir of reducing capacity in many subsurface environments that may contribute to the reduction of contaminants such as U VI. We have examined the uptake and reduction of U VI in the presence of biogenic green rust (BioGR), magnetite (BioMAG), and siderite (BioSID) formed during the reduction of Fe III oxides by Shewanella putrefaciens CN32. Within 48 h, total solution-phase U VI concentrations decreased from 500 µM to 1.5 µM, 392 µM, and 472 µM in the U-BioGR, U-BioMAG, and U-BioSID systems, respectively. Analysis of the samples by U L III extended X-ray absorption fine structure spectroscopy (EXAFS) indicated that despite a stoichiometric excess of Fe II , no more than
Environmental Microbiology, 2014
We reconstructed the complete 2.4 Mb-long genome of a previously uncultivated epsilonproteobacter... more We reconstructed the complete 2.4 Mb-long genome of a previously uncultivated epsilonproteobacterium, Candidatus Sulfuricurvum sp. RIFRC-1, via assembly of shortread shotgun metagenomic data using a complexity reduction approach. Genome-based comparisons indicate the bacterium is a novel species within the Sulfuricurvum genus, which contains one cultivated representative, S. kujiense. Divergence between the species appears due in part to extensive genomic rearrangements, gene loss, and chromosomal versus plasmid encoding of certain (respiratory) genes by RIFRC-1. DNA for the genome was obtained from terrestrial aquifer sediment, in which RIFRC-1 comprised ~47% of the bacterial community. Genomic evidence suggests RIFRC-1 is a chemolithoautotrophic diazotroph capable of deriving energy for growth by microaerobic or nitrate-/nitric oxide-dependent oxidation of S 0 , sulfide or sulfite, or H 2 oxidation. Carbon may be fixed via the reductive tricarboxylic acid cycle. Consistent with these physiological attributes, the local aquifer was microoxic with small concentrations of available nitrate, small but elevated concentrations of reduced sulfur, and NH 4 + /NH 3limited. Additionally, various mechanisms for heavy metal and metalloid tolerance and virulence point to a lifestyle well-adapted for metal(loid)-rich environments, and a shared evolutionary past with pathogenic Epsilonproteobacteria. Results expand upon recent findings highlighting the potential importance of sulfur and hydrogen metabolism in the terrestrial subsurface.
Minerals, 2021
Fe(II)-bearing minerals (magnetite, siderite, green rust, etc.) are common products of microbial ... more Fe(II)-bearing minerals (magnetite, siderite, green rust, etc.) are common products of microbial Fe(III) reduction, and they provide a reservoir of reducing capacity in many subsurface environments that may contribute to the reduction of redox active elements such as vanadium; which can exist as V(V), V(IV), and V(III) under conditions typical of near-surface aquatic and terrestrial environments. To better understand the redox behavior of V under ferrugenic/sulfidogenic conditions, we examined the interactions of V(V) (1 mM) in aqueous suspensions containing 50 mM Fe(II) as magnetite, siderite, vivianite, green rust, or mackinawite, using X-ray absorption spectroscopy at the V K-edge to determine the valence state of V. Two additional systems of increased complexity were also examined, containing either 60 mM Fe(II) as biogenic green rust (BioGR) or 40 mM Fe(II) as a mixture of biogenic siderite, mackinawite, and magnetite (BioSMM). Within 48 h, total solution-phase V concentrations...
Minerals
Aluminosilicate clay minerals are often a major component of soils and sediments and many of thes... more Aluminosilicate clay minerals are often a major component of soils and sediments and many of these clays contain structural Fe (e.g., smectites and illites). Structural Fe(III) in smectite clays is redox active and can be reduced to Fe(II) by biotic and abiotic processes. Fe(II)-bearing minerals such as magnetite and green rust can reduce Hg(II) to Hg(0); however, the ability of other environmentally relevant Fe(II) phases, such as structural Fe(II) in smectite clays, to reduce Hg(II) is largely undetermined. We conducted experiments examining the potential for reduction of Hg(II) by smectite clay minerals containing 0–25 wt% Fe. Fe(III) in the clays (SYn-1 synthetic mica-montmorillonite, SWy-2 montmorillonite, NAu-1 and NAu-2 nontronite, and a nontronite from Cheney, Washington (CWN)) was reduced to Fe(II) using the citrate-bicarbonate-dithionite method. Experiments were initiated by adding 500 µM Hg(II) to reduced clay suspensions (4 g clay L−1) buffered at pH 7.2 in 20 mM 3-morph...
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Papers by Edward J O'Loughlin