Mobilisation of arsenic, selenium and uranium from Carboniferous black shales in west Ireland

Armstrong, Joe; Parnell, John; Bullock, Liam A.; Boyce, Adrian J.; Perez, Magali; Feldmann, Jörg

doi:10.1016/j.apgeochem.2019.104401

Cited by 27 publications

(11 citation statements)

References 90 publications

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“…Heavy metals such as arsenic and cadmium are commonly associated with pyrite in organic-rich shales (Wang et al, 2016;Armstrong et al, 2019) and are released when pyrite is dissolved. This indicates that pyrite dissolution can pose a challenge for produced water treatment.…”

Section: Mineralmentioning

confidence: 99%

“…Concurrent oxidation of BTEX and shale organic matter in the SH-HFF (-CO 3 ) experiment is supported by evidence of increased shale organic matter oxidation. Uranium in shale is associated with organic matter and is released into solution under oxidizing conditions when organic matter is broken down (Armstrong et al, 2019). Elevated concentration of uranium in the SH-HFF (-CO 3 ) fluids relative to the other samples suggests that it is released from the shale (Figure 2).…”

Section: Btex Oxidationmentioning

confidence: 99%

“…Changes in flow dynamics from precipitation reactions have been implicated as a potential cause for discrepancies between modeled and actual late-stage hydrocarbon production in hydraulically fractured wells (Jew et al, 2017). Dissolution of shale minerals and organic matter degradation can increase the porosity and permeability of shale but increases the toxicity of produced waters (Harrison et al, 2017;Armstrong et al, 2019;Sharma et al, 2020;Donmoyer et al, 2021) and the risks posed by produced water spills.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Carbonate Minerals on Shale-Hydraulic Fracturing Fluid Interactions in the Marcellus Shale

et al. 2021

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Natural gas extracted from tight shale formations, such as the Marcellus Shale, represents a significant and developing front in energy exploration. By fracturing these formations using pressurized fracturing fluid, previously unobtainable hydrocarbon reserves may be tapped. While pursuing this resource, hydraulic fracturing operations leave chemically complex fluids in the shale formation for at least two weeks. This provides a substantial opportunity for the hydraulic fracturing fluid (HFF) to react with the shale formation at reservoir temperature and pressure. In this study, we investigated the effects of the carbonates on shale-HFF reactions with a focus on the Marcellus Shale. We performed autoclave experiments at high temperature and pressure reservoir conditions using a carbonate-rich and a decarbonated or carbonate-free version of the same shale sample. We observed that carbonate minerals buffer the pH of the solution, which in turn prevents clay dissolution. Carbonate and bicarbonate ions also scavenge reactive oxidizing species (ROS), which prevents oxidation of shale organic matter and volatile organic compounds (VOCs). Carbonate-free samples also show higher pyrite dissolution compared to the carbonate-rich sample due to chelation reactions. This study demonstrates how carbonate minerals (keeping all other variables constant) affect shale-HFF reactions that can potentially impact porosity, microfracture integrity, and the release of heavy metals and volatile organic contaminants in the produced water.

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Section: Mineralmentioning

confidence: 99%

Section: Btex Oxidationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Carbonate Minerals on Shale-Hydraulic Fracturing Fluid Interactions in the Marcellus Shale

et al. 2021

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“…Iron concentrations in the ditch are much lower though, than in the groundwater, supposedly due to precipitation of iron oxyhydroxides when reaching neutral and oxidizing surface water (cf. Armstrong et al 2019).…”

Section: Solubility Controlmentioning

confidence: 99%

Groundwater chemistry affected by trace elements (As, Mo, Ni, U and V) from a burning alum shale waste deposit, Kvarntorp, Sweden

Åhlgren

Sjöberg

Allard

et al. 2021

Environ Sci Pollut Res

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Worldwide, black shales and shale waste are known to be a potential source of metals to the environment. This project demonstrates ongoing weathering and evaluates leaching processes at a 100-m-high shale waste deposit closed in the 1960s. Some deep parts of the deposit are still burning with temperatures exceeding 500 °C. To demonstrate ongoing weathering and leaching, analyses of groundwater and solid samples of shale and shale waste have been undertaken. Largest impact on groundwater quality was observed downstream the deposit, where elevated temperatures also indicate a direct impact from the burning waste deposit. Groundwater quality is largely controlled by pH and redox conditions (e.g., for arsenic, nickel, molybdenum, uranium and vanadium), and the mixture of different waste materials, including pyrite (acidic leachates) and carbonates (neutralizing and buffering pH). Analyses of shale waste from the deposit confirm the expected pyrite weathering with high concentrations of iron, nickel and uranium in the leachates. No general time trends could be distinguished for the groundwater quality from the monitoring in 2004–2019. This study has shown that black shale waste deposits can have a complex long-term impact on the surrounding environment.

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“…For instance, interactions between hydraulic fracturing fluids and Eagle Ford shale samples were found to increase pyrite mobilization by 1 order of magnitude because of particle detachment following carbonate dissolution . Given that toxic elements, especially arsenic, are typically constituents within iron sulfides and sorbates on iron oxy-hydroxides, , acid erosion of fracture surfaces may increase arsenic mobilization, which is an environmental concern in many subsurface practices. − …”

Section: Introductionmentioning

confidence: 99%

Acid Erosion of Carbonate Fractures and Accessibility of Arsenic-Bearing Minerals: In Operando Synchrotron-Based Microfluidic Experiment

Deng

Fitts

Tappero

et al. 2020

Environ. Sci. Technol.

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Underground flows of acidic fluids through fractured rock can create new porosity and increase accessibility to hazardous trace elements such as arsenic. In this study, we developed a custom microfluidic cell for an in operando synchrotron experiment using X-ray attenuation. The experiment mimics reactive fracture flow by passing an acidic fluid over a surface of mineralogically heterogeneous rock from the Eagle Ford shale. Over 48 h, calcite was preferentially dissolved, forming an altered layer 200–500 μm thick with a porosity of 63–68% and surface area >10× higher than that in the unreacted shale as shown by xCT analyses. Calcite dissolution rate quantified from the attenuation data was 3 × 10–4 mol/m2s and decreased to 3 × 10–5 mol/m2s after 24 h because of increasing diffusion limitations. Erosion of the fracture surface increased access to iron-rich minerals, thereby increasing access to toxic metals such as arsenic. Quantification using XRF and XANES microspectroscopy indicated up to 0.5 wt % of As(-I) in arsenopyrite and 1.2 wt % of As(V) associated with ferrihydrite. This study provides valuable contributions for understanding and predicting fracture alteration and changes to the mobilization potential of hazardous metals and metalloids.

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Mobilisation of arsenic, selenium and uranium from Carboniferous black shales in west Ireland

Cited by 27 publications

References 90 publications

Effects of Carbonate Minerals on Shale-Hydraulic Fracturing Fluid Interactions in the Marcellus Shale

Effects of Carbonate Minerals on Shale-Hydraulic Fracturing Fluid Interactions in the Marcellus Shale

Groundwater chemistry affected by trace elements (As, Mo, Ni, U and V) from a burning alum shale waste deposit, Kvarntorp, Sweden

Acid Erosion of Carbonate Fractures and Accessibility of Arsenic-Bearing Minerals: In Operando Synchrotron-Based Microfluidic Experiment

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