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Soil Systems
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Redox Processes and Characterization of Contaminated Soil, Groundwater, and Aquifer...
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Redox Processes and Characterization of Contaminated Soil, Groundwater, and Aquifer Sediments

A special issue of Soil Systems (ISSN 2571-8789).

Deadline for manuscript submissions: closed (30 November 2020) | Viewed by 25661

Special Issue Editor

Dr. Richard Wilkin

E-Mail Website
Guest Editor
United States Environmental Protection Agency, Groundwater Characterization and Remediation Division, Washington, DC, USA
Interests: evaluation of methods for characterizing the redox state of contaminated groundwater; sediments; and soils; geochemistry of reactive iron minerals such as iron sulfides and green rusts; laboratory and field investigations that explore the permeable reactive barrier technology for treating inorganic and organic contaminants in groundwater

Special Issue Information

Dear Colleagues,

Characterization of the redox state of subsurface systems in time and space often underpins site contaminant transport and fate models and factors into the design and development of sustainable remediation strategies. This Special Issue will explore aspects of redox characterization in soil/groundwater/aquifer systems. Emphasis is placed on common redox-sensitive groundwater contaminants, such as chromium (Cr), arsenic (As), and uranium (U) and redox-sensitive elements that influence contaminant behavior, such as iron (Fe), manganese (Mn), and sulfur (S). Contributions will utilize lab-based, field-based, and modeling studies to provide insight on how redox-sensitive species are mobilized, attenuated, and/or impact other co-contaminants in subsurface systems.

Dr. Richard Wilkin
Guest Editor

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Keywords

  • Redox
  • Groundwater
  • Chromium
  • Arsenic
  • Uranium

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Published Papers (6 papers)

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Research

24 pages, 10124 KiB  
Article
Field, Laboratory and Modeling Evidence for Strong Attenuation of a Cr(VI) Plume in a Mudstone Aquifer Due to Matrix Diffusion and Reaction Processes
by Steven Chapman, Beth Parker, Tom Al, Richard Wilkin, Diana Cutt, Katherine Mishkin and Shane Nelson
Soil Syst. 2021, 5(1), 18; https://doi.org/10.3390/soilsystems5010018 - 16 Mar 2021
Cited by 2 | Viewed by 3048
Abstract
This study uses a combination of conventional and high resolution field and laboratory methods to investigate processes causing attenuation of a hexavalent chromium (Cr(VI)) plume in sedimentary bedrock at a former industrial facility. Groundwater plume Cr(VI) [...] Read more.
This study uses a combination of conventional and high resolution field and laboratory methods to investigate processes causing attenuation of a hexavalent chromium (Cr(VI)) plume in sedimentary bedrock at a former industrial facility. Groundwater plume Cr(VI) concentrations decline by more than three orders of magnitude over a 900 m distance down gradient from the site. Internal plume concentrations generally exhibit stable to declining trends due to diffusive and reactive transport in the low permeability matrix as fluxes from the contamination source dissipate due to natural depletion processes and active remediation efforts. The strong attenuation is attributed to diffusion from mobile groundwater in fractures to immobile porewater in the rock matrix, and reactions causing transformation of aqueous Cr(VI) to low-solubility Cr(III) precipitates, confirmed by high spatial resolution rock matrix contaminant concentrations and comparisons with groundwater concentrations from multi-level sampling within the plume. Field characterization data for the fracture network and matrix properties were used to inform 2-D discrete-fracture matrix (DFM) numerical model simulations that quantify attenuation due to diffusion and reaction processes, which show consistency with field datasets, and provide insights regarding future plume conditions. The combination of field, laboratory and modeling evidence demonstrates effects of matrix diffusion and reaction processes causing strong attenuation of a Cr(VI) plume in a sedimentary bedrock aquifer. This approach has important implications for characterization of sites with Cr(VI) contamination for improved site conceptual models and remediation decision-making. Full article
(This article belongs to the Special Issue Redox Processes and Characterization of Contaminated Soil, Groundwater, and Aquifer Sediments)
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20 pages, 1139 KiB  
Article
Pteris vittata Arsenic Accumulation Only Partially Explains Soil Arsenic Depletion during Field-Scale Phytoextraction
by Sarick Matzen, Sirine Fakra, Peter Nico and Céline Pallud
Soil Syst. 2020, 4(4), 71; https://doi.org/10.3390/soilsystems4040071 - 4 Dec 2020
Cited by 12 | Viewed by 3376
Abstract
Soil arsenic heterogeneity complicates our understanding of phytoextraction rates during arsenic phytoextraction with Pteris vittata, including in response to rate stimulation with nutrient treatments. In a 58-week arsenic phytoextraction field study, we determined the effects of soil arsenic concentrations, fertilizer application, and [...] Read more.
Soil arsenic heterogeneity complicates our understanding of phytoextraction rates during arsenic phytoextraction with Pteris vittata, including in response to rate stimulation with nutrient treatments. In a 58-week arsenic phytoextraction field study, we determined the effects of soil arsenic concentrations, fertilizer application, and mycorrhizal fungi inoculation on P. vittata arsenic uptake rates, soil arsenic depletion, and arsenic soil–plant mass balances. Initial soil arsenic concentrations were positively correlated with arsenic uptake rates. Soil inoculation with mycorrhizal fungus Funneliformis mosseae led to 1.5–2 times higher fern aboveground biomass. Across all treatments, ferns accumulated a mean of 3.6% of the initial soil arsenic, and mean soil arsenic concentrations decreased by up to 44%. At depths of 0–10 cm, arsenic accumulation in P. vittata matched soil arsenic depletion. However, at depths of 0–20 cm, fern arsenic accumulation could not account for 61.5% of the soil arsenic depletion, suggesting that the missing arsenic could have been lost to leaching. A higher fraction of arsenic (III) (12.8–71.5%) in the rhizosphere compared to bulk soils suggests that the rhizosphere is a distinct geochemical environment featuring processes that could solubilize arsenic. To our knowledge, this is the first mass balance relating arsenic accumulation in P. vittata to significant decreases in soil arsenic concentrations under field conditions. Full article
(This article belongs to the Special Issue Redox Processes and Characterization of Contaminated Soil, Groundwater, and Aquifer Sediments)
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16 pages, 2119 KiB  
Article
Removal of Arsenate and Arsenite in Equimolar Ferrous and Ferric Sulfate Solutions through Mineral Coprecipitation: Formation of Sulfate Green Rust, Goethite, and Lepidocrocite
by Chunming Su and Richard T. Wilkin
Soil Syst. 2020, 4(4), 68; https://doi.org/10.3390/soilsystems4040068 - 23 Nov 2020
Cited by 5 | Viewed by 3175
Abstract
An improved understanding of in situ mineralization in the presence of dissolved arsenic and both ferrous and ferric iron is necessary because it is an important geochemical process in the fate and transformation of arsenic and iron in groundwater systems. This work aimed [...] Read more.
An improved understanding of in situ mineralization in the presence of dissolved arsenic and both ferrous and ferric iron is necessary because it is an important geochemical process in the fate and transformation of arsenic and iron in groundwater systems. This work aimed at evaluating mineral phases that could form and the related transformation of arsenic species during coprecipitation. We conducted batch tests to precipitate ferrous (133 mM) and ferric (133 mM) ions in sulfate (533 mM) solutions spiked with As (0–100 mM As(V) or As(III)) and titrated with solid NaOH (400 mM). Goethite and lepidocrocite were formed at 0.5–5 mM As(V) or As(III). Only lepidocrocite formed at 10 mM As(III). Only goethite formed in the absence of added As(V) or As(III). Iron (II, III) hydroxysulfate green rust (sulfate green rust or SGR) was formed at 50 mM As(III) at an equilibrium pH of 6.34. X-ray analysis indicated that amorphous solid products were formed at 10–100 mM As(V) or 100 mM As(III). The batch tests showed that As removal ranged from 98.65–100%. Total arsenic concentrations in the formed solid phases increased with the initial solution arsenic concentrations ranging from 1.85–20.7 g kg−1. Substantial oxidation of initially added As(III) to As(V) occurred, whereas As(V) reduction did not occur. This study demonstrates that concentrations and species of arsenic in the parent solution influence the mineralogy of coprecipitated solid phases, which in turn affects As redox transformations. Full article
(This article belongs to the Special Issue Redox Processes and Characterization of Contaminated Soil, Groundwater, and Aquifer Sediments)
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28 pages, 2207 KiB  
Article
Investigating the Potential Impact of Louisiana Coastal Restoration on the Trace Metal Geochemistry of Constructed Marshlands
by Omolola A. Akintomide, Segun A. Adebayo, Alexandra S. Trahan, Elizabeth Chamberlain and Karen H. Johannesson
Soil Syst. 2020, 4(3), 55; https://doi.org/10.3390/soilsystems4030055 - 5 Sep 2020
Cited by 2 | Viewed by 3762
Abstract
Coastal restoration through diversion of suspended sediments from the Lower Mississippi River (LMR) into hydrologically isolated marshlands of Mid-Barataria Bay and Mid-Breton Sounds in southern Louisiana has the potential to mobilize lead (Pb), and other trace elements. We investigate the potential impact(s) of [...] Read more.
Coastal restoration through diversion of suspended sediments from the Lower Mississippi River (LMR) into hydrologically isolated marshlands of Mid-Barataria Bay and Mid-Breton Sounds in southern Louisiana has the potential to mobilize lead (Pb), and other trace elements. We investigate the potential impact(s) of the diversion on marsh porewater through analysis of modern riverbank and suspended sediments, compared to sediments from pre-industrial deltaic deposits of LMR. Sequential extraction methods were used to evaluate Pb, cobalt (Co), copper (Cu), nickel (Ni), and zinc (Zn) in the sediments. Our results show that metal contents are higher (e.g., 8- to 10-fold for Pb) in the modern sediments relative to pre-industrial deposits. Also, the reducible fraction, presumably iron/manganese (Fe/Mn) oxides/oxyhydroxides, is the chief reservoir of environmentally available metals. The substantially higher trace metal contents of the modern relative to pre-industrial sediments suggest that the modern sediments contain a sizeable amount of anthropogenic contributions. Furthermore, the concentration of the trace metals in the reducible fraction suggests bioavailability to marsh organisms upon reductive dissolution within the planned, constructed coastal marshes. Still, additional sediment samples from the marshlands during the diversion implementation phase will be necessary to support the preliminary findings in this contribution as it affects coastal marshes and vital local fisheries. Full article
(This article belongs to the Special Issue Redox Processes and Characterization of Contaminated Soil, Groundwater, and Aquifer Sediments)
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19 pages, 5794 KiB  
Article
Manganese (Mn) Concentrations and the Mn-Fe Relationship in Shallow Groundwater: Implications for Groundwater Monitoring
by Kay Hamer, Imke Gudenschwager and Thomas Pichler
Soil Syst. 2020, 4(3), 49; https://doi.org/10.3390/soilsystems4030049 - 5 Aug 2020
Cited by 20 | Viewed by 4571
Abstract
Manganese (Mn) concentrations in approximately 32,000 groundwater analyses from more than 4800 monitoring wells in northern Germany were evaluated. This region was considered well suited to study Mn in shallow groundwater in unconsolidated sediments. Spearman rank correlation was used to correlate between redox-sensitive [...] Read more.
Manganese (Mn) concentrations in approximately 32,000 groundwater analyses from more than 4800 monitoring wells in northern Germany were evaluated. This region was considered well suited to study Mn in shallow groundwater in unconsolidated sediments. Spearman rank correlation was used to correlate between redox-sensitive parameters and the Mann–Kendall test for an evaluation of temporal trends. Manganese concentrations varied over two orders of magnitude and more than 40% of the wells had concentrations above 0.3 mg/L. Median Mn concentrations in the major hydrogeological units, the Geesten, tidal wetlands, and fluviatile lowlands were 0.12 mg/L, 0.46 mg/L, and 0.27 mg/L, respectively. Separating the data by land use, the median concentrations were 0.20 mg/L for arable land, 0.15 mg/L for forests, and 0.24 for grassland. Calculated background concentrations of Mn varied from <0.25 mg/L to 4.79 mg/L. A new parameter, ∆Mn-Fe, defined as the concentration difference between Mn and Fe in mg/L together with nitrate concentrations exceeding 50 mg/L was used to identify the fertilizer-borne input of nitrate. However, the factor controlling Mn occurrence seemingly was the depth of monitoring wells and the screen-length. Elevated concentrations of Mn and a high ∆Mn-Fe were generally found in shallow wells and wells with short screen-lengths. Full article
(This article belongs to the Special Issue Redox Processes and Characterization of Contaminated Soil, Groundwater, and Aquifer Sediments)
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19 pages, 2921 KiB  
Article
From Plant to Paddy—How Rice Root Iron Plaque Can Affect the Paddy Field Iron Cycling
by Markus Maisch, Ulf Lueder, Andreas Kappler and Caroline Schmidt
Soil Syst. 2020, 4(2), 28; https://doi.org/10.3390/soilsystems4020028 - 30 Apr 2020
Cited by 27 | Viewed by 6632
Abstract
Iron plaque on rice roots represents a sink and source of iron in paddy fields. However, the extent of iron plaque in impacting paddy field iron cycling is not yet fully deciphered. Here, we followed iron plaque formation during plant growth in laboratory-controlled [...] Read more.
Iron plaque on rice roots represents a sink and source of iron in paddy fields. However, the extent of iron plaque in impacting paddy field iron cycling is not yet fully deciphered. Here, we followed iron plaque formation during plant growth in laboratory-controlled setups containing a transparent soil matrix. Using image analysis, microsensor measurements, and mineral extractions, we demonstrate that radial oxygen loss (ROL) is the main driver for rhizosphere iron oxidation. While O2 was restricted to the vicinity of roots, root tips showed highest spatio-temporal variation in ROL (<5–50 µM) following diurnal patterns. Iron plaque covered >30% of the total root surface corresponding to 60–180 mg Fe(III) per gram dried root and gradually transformed from low-crystalline minerals (e.g., ferrihydrite) on root tips, to >20% higher-crystalline minerals (e.g., goethite) within 40 days. Iron plaque exposed to an Fe(III)-reducing Geobacter spp. culture resulted in 30% Fe(II) remobilization and >50% microbial transformation to Fe(II) minerals (e.g., siderite, vivianite, and Fe–S phases) or persisted by >15% as Fe(III) minerals. Based on the collected data, we estimated that iron plaque formation and reductive dissolution can impact more than 5% of the rhizosphere iron budget which has consequences for the (im)mobilization of soil contaminants and nutrients. Full article
(This article belongs to the Special Issue Redox Processes and Characterization of Contaminated Soil, Groundwater, and Aquifer Sediments)
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