Microbially mediated iron redox cycling of subsurface sediments from Hanford Site, Washington State, USA

The U.S. Department of Energy Hanford Site, formerly used for nuclear weapons production, encompasses 1500 square kilometers in southeast Washington State along the Columbia River. A principle threat to the river are the groundwater plumes of hexavalent chromium (Cr(VI)), which affect approximately 9.8 square kilometers, and 4.1 kilometers of shoreline. Cleanup goals are to stop Cr(VI) from entering the river by the end of 2012 and remediate the groundwater plumes to the drinking water standards by the end of 2020. Five groundwater pump-and-treat systems are currently in operation for the remediation of Cr(VI). Since the 1990s, over 13.6 billion L of groundwater have been treated; over 1,435 kg of Cr(VI) have been removed. This paper describes the unique aspects of the site, its environmental setting, hydrogeology, groundwater-river interface, riverine hydraulic effects, remediation activities completed to date, a summary of the current and proposed pump-and-treat operations, the in situ redox manipulation barrier, and the effectiveness of passive barriers, resins, and treatability testing results of calcium polysulfide, biostimulation, and electrocoagulation, currently under evaluation.

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Impact of ecohydrological fluctuations on iron-redox cycling

Soil Biology and Biochemistry ◽

10.1016/j.soilbio.2019.03.013 ◽

2019 ◽

Vol 133 ◽

pp. 188-195 ◽

Cited By ~ 1

Author(s):

Salvatore Calabrese ◽

Amilcare Porporato

Keyword(s):

Redox Cycling ◽

Iron Redox

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Induction of Gamma-Glutamyltransferase Activity and Consequent Pro-oxidant Reactions in Human Macrophages Exposed to Crocidolite Asbestos

Toxicological Sciences ◽

10.1093/toxsci/kfz175 ◽

2019 ◽

Vol 177 (2) ◽

pp. 476-482 ◽

Cited By ~ 1

Author(s):

Alessandro Corti ◽

Justine Bonetti ◽

Silvia Dominici ◽

Simona Piaggi ◽

Vanna Fierabracci ◽

...

Keyword(s):

Oxidative Stress ◽

Hydroxyl Radical ◽

Fenton Reaction ◽

Redox Cycling ◽

Pathogenic Potential ◽

Gamma Glutamyltransferase ◽

Reduction Of Iron ◽

Healthy Donors ◽

Iron Redox

Abstract Asbestos is the main causative agent of malignant pleural mesothelioma. The variety known as crocidolite (blue asbestos) owns the highest pathogenic potential, due to the dimensions of its fibers as well as to its content of iron. The latter can in fact react with macrophage-derived hydrogen peroxide in the so called Fenton reaction, giving rise to highly reactive and mutagenic hydroxyl radical. On the other hand, hydroxyl radical can as well originate after thiol-dependent reduction of iron, a process capable of starting its redox cycling. Previous studies showed that glutathione (GSH) is one such thiol, and that cellular gamma-glutamyltransferase (GGT) can efficiently potentiate GSH-dependent iron redox cycling and consequent oxidative stress. As GGT is expressed in macrophages and is released upon their activation, the present study was aimed at verifying the hypothesis that GSH/GGT-dependent redox reactions may participate in the oxidative stress following the activation of macrophages induced by crocidolite asbestos. Experiments in acellular systems confirmed that GGT-mediated metabolism of GSH can potentiate crocidolite-dependent production of superoxide anion, through the production of highly reactive dipeptide thiol cysteinyl-glycine. Cultured THP-1 macrophagic cells, as well as isolated monocytes obtained from healthy donors and differentiated to macrophages in vitro, were investigated as to their expression of GGT and the effects of exposure to crocidolite. The results show that crocidolite asbestos at subtoxic concentrations (50–250 ng/1000 cells) can upregulate GGT expression, which raises the possibility that macrophage-initiated, GSH/GGT-dependent pro-oxidant reactions may participate in the pathogenesis of tissue damage and inflammation consequent to crocidolite intoxication.

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Microbial iron-redox cycling in subsurface environments

Biochemical Society Transactions ◽

10.1042/bst20120202 ◽

2012 ◽

Vol 40 (6) ◽

pp. 1249-1256 ◽

Cited By ~ 62

Author(s):

Eric E. Roden

Keyword(s):

Electron Transfer ◽

Iron Oxidation ◽

Anaerobic Respiration ◽

Redox Cycling ◽

Rapid Expansion ◽

Extracellular Electron Transfer ◽

Experimental Systems ◽

Subsurface Environments ◽

Micro Organisms ◽

Iron Redox

In addition to its central role in mediating electron-transfer reactions within all living cells, iron undergoes extracellular redox transformations linked to microbial energy generation through utilization of Fe(II) as a source of chemical energy or Fe(III) as an electron acceptor for anaerobic respiration. These processes permit microbial populations and communities to engage in cyclic coupled iron oxidation and reduction within redox transition zones in subsurface environments. In the present paper, I review and synthesize a few case studies of iron-redox cycling in subsurface environments, highlighting key biochemical aspects of the extracellular iron-redox metabolisms involved. Of specific interest are the coupling of iron oxidation and reduction in field and experimental systems that model redox gradients and fluctuations in the subsurface, and novel pathways and organisms involved in the redox cycling of insoluble iron-bearing minerals. These findings set the stage for rapid expansion in our knowledge of the range of extracellular electron-transfer mechanisms utilized by subsurface micro-organisms. The observation that closely coupled oxidation and reduction of iron can take place under conditions common to the subsurface motivates this expansion in pursuit of molecular tools for studying iron-redox cycling communities in situ.

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