Persistence of chromate in vadose zone and aquifer sediments in Hanford, Washington

Szecsody, Jim E.; Truex, M. J.; Qafoku, Nikolla P.; McKinley, James P.; Ivarson, Kristine A.; Pietro, Silvina Di

doi:10.1016/j.scitotenv.2019.04.173

Cited by 7 publications

(10 citation statements)

References 56 publications

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“…In contrast, anthropogenic Cr released to subsurface sediments is typically released as Cr(VI), but can precipitate as Cr(VI) or Cr(III) phases, depending on the redox environment (Qafoku et al 2003, 2010). The Cr(VI) phases include aqueous and adsorbed Cr, CaCrO 4 , and BaCrO 4 (Szecsody et al 2019). Sediment R28 contains considerable anthropogenic Cr as BaCrO 4 , which has a low solubility and low leaching, and a 10 PV leach removed 0.0373 μg/g Cr.…”

Section: Resultsmentioning

confidence: 99%

“…Six increasingly acidic sequential extractions were used in this investigation that included: (1) artificial groundwater (AGW), (2) ion exchange solution, (3) pH 5 acetate solution, (4) pH 2.3 acetic acid, (5) oxalic acid, and (6) nitric acid, where target Cr phases are described in Table 2 (Szecsody et al 2019). Extraction 3 (pH 5 acetate solution) is operationally defined as the carbonate that dissolves in a weak acetate solution (pH 5) in 1 h in contrast to the 5‐day acetic acid extraction (extraction 4, pH 2.3), which dissolves most carbonates in the 5‐day extraction.…”

Section: Methodsmentioning

confidence: 99%

“…A relatively short SF event (i.e., 16 h after the start) was applied at the beginning of these experiments because aqueous and adsorbed Cr are usually rapidly leached (with the first PV). Later during leaching, Cr is usually released from dissolution of calcite, Fe oxides, and potentially other phases, so longer SF durations were applied (Qafoku et al 2009; Szecsody et al 2019). Changes in contaminant effluent concentration before and after the SF and the length of the SF events were used to calculate the Cr rates from the sediments (expressed in μg contaminant/g of sediment/day).…”

Section: Methodsmentioning

confidence: 99%

“…Despite many efforts over the last few decades to remediate hexavalent chromium (Cr(VI)) contaminated sites around the world (Jacobs and Testa 2005), Cr(VI) contamination persists in many soils, subsoils, and sediments (Szecsody et al 2019; Rockhold et al 2020). This is a major concern because the oxidized hexavalent form, Cr(VI), has a higher toxicity than the reduced, mostly immobile, trivalent form, Cr(III).…”

Section: Introductionmentioning

confidence: 99%

“…Cr contamination persists in the vadose zone due to geochemical and physical processes. The majority of Cr at the site was released as aqueous chromate (CrO 4 2− ) that exhibits nearly no adsorption to sediments under neutral and slightly alkaline conditions (Zachara et al 1989, 2004; Qafoku et al 2009; Szecsody et al 2019) or near‐surface releases of acidic, high‐concentration sodium dichromate (Na 2 Cr 2 O 7 ). Considerable chromate adsorption and partial reduction has been observed under acidic conditions (Stanin 2005; Dresel et al 2008; Qafoku et al 2010).…”

Section: Introductionmentioning

confidence: 99%

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Vadose Zone Soil Flushing for Chromium Remediation: A Laboratory Investigation to Support Field‐scale Application

Szecsody¹,

Emerson²,

Lawter³

et al. 2023

Groundwater Monitoring Rem

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Cr(VI) flushing from the vadose zone to the groundwater (with subsequent Cr(VI) removal in groundwater by pump‐and‐treat system) is a promising remedial technique that has recently been used at field scale. This laboratory study was conducted to provide the technical basis to design a field soil flushing strategy. The objectives were to (1) quantify the relationship between sediment Cr(VI) and Cr(III) mass and release rates and subsequent Cr(VI) leaching; (2) investigate different methodologies to maximize Cr(VI) leaching, and (3) investigate methods to minimize leaching of remaining residual Cr. Characterization of Cr‐contaminated sediments (Hanford Site, WA) exhibited Cr(VI) showed that leach rates that were correlated to different Cr surface phases. Sediments with low leachable Cr(VI) (<2 μg/g) leached Cr rapidly, so slow infiltration of water in a single pulse was sufficient to leach most Cr. In contrast, sediments with high Cr (2 to 200 μg/g) released some Cr(VI) quickly but 10 to 50% Cr(VI) slowly (tens to hundreds of hours). Efficient unsaturated leaching of these sediments required a different infiltration strategy that includes: multiple slow leach pulses with time between flushing cycles; the use of a surfactant to increase Cr leaching from low‐permeability zones, and the use of a reductant (Na‐dithionite or Ca‐polysulfide) in the final leach water was highly effective at decreasing residual Cr leaching. This study clearly demonstrated that the methodology of basing laboratory Cr flushing on parameters such as Cr release mass and rates could be used to improve the efficiency of soil flushing at field scale.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Vadose Zone Soil Flushing for Chromium Remediation: A Laboratory Investigation to Support Field‐scale Application

Szecsody¹,

Emerson²,

Lawter³

et al. 2023

Groundwater Monitoring Rem

Self Cite

View full text Add to dashboard Cite

show abstract

Aluminum hydroxide colloid facilitated transport of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) in porous media

Qiu

Liu

et al. 2020

Chemosphere

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Electro-enhanced leaching method for the mobilization of Cr(VI) in contaminated groundwater aquifer

Zhang

et al. 2020

Sci Rep

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Removal of hexavalent chromium [Cr(VI)] from soils and water has been widely studied for its high toxicity. Although leaching method is viewed as an effective approach to eliminate Cr(VI) and some studies attempted to enhance leaching performance via the external electric field, there is little knowledge about the influential factor in electro-leaching system on Cr(VI) removal performance. In this study, an electro-leaching technology was developed for removing Cr(VI) from groundwater aquifer to comprehensively discuss the correlation between the operational parameters and Cr(VI) removal efficiency. When the applied voltage was 20 V and the initial Cr(VI) concentration was 40 mg/kg, Cr(VI) removal efficiency achieved 99.9% in 120 min in the electro-leaching system, 15% higher than the system without the electric field. Cr(VI) removal efficiencies increased with the voltage demonstrating the significant enhancement of the electro-leaching method in removing Cr(VI). When Cr(VI) concentration climbed to 120 mg/kg, Cr(VI) removal efficiency remained above 85%. The effects of different voltages, Cr(VI) concentrations, pollutant distribution and salt content of leaching solution on the leaching effect were also investigated. Meanwhile, the relationship between the current intensity change and the amount of removed Cr(VI) during the electro-leaching process was first investigated, and the relevant model was fitted. There is a quadratic linear correlation between the amount of current change and the amount of removed Cr(VI). This novel electro-enhanced leaching method can effectively remove Cr(VI) from contaminated groundwater aquifer by enhancing the migration of charged contaminant ions during the leaching process, and it is worthy of further study of heavy metal remediation.

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Persistence of chromate in vadose zone and aquifer sediments in Hanford, Washington

Cited by 7 publications

References 56 publications

Vadose Zone Soil Flushing for Chromium Remediation: A Laboratory Investigation to Support Field‐scale Application

Vadose Zone Soil Flushing for Chromium Remediation: A Laboratory Investigation to Support Field‐scale Application

Aluminum hydroxide colloid facilitated transport of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) in porous media

Electro-enhanced leaching method for the mobilization of Cr(VI) in contaminated groundwater aquifer

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