Characterization of dissolved organic matter in anoxic rock extracts and in situ pore water of the Opalinus Clay

Courdouan, Amandine; Christl, Iso; Meylan, Sébastien; Wersin, Paul; Kretzschmar, Ruben

doi:10.1016/j.apgeochem.2007.09.001

Cited by 73 publications

(68 citation statements)

References 23 publications

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“…Such analyses of total organic matter typically yield peaks near 285, 286.7, and 288.6 eV Scheinost et al, 2001;Solomon et al, 2005Solomon et al, , 2007a) similar to humic substances isolated from groundwater (Schäfer et al, 2003. In comparison, DOC characterized in pore water of rock formations showed dominance of peak energy at 288.5 eV, which is indicative of carboxylic C forms with only small features slightly around 285.0 eV (Courdouan et al, 2007).…”

Section: Resolving Key Questions In Soil Biogeochemistrymentioning

confidence: 99%

Organic Carbon Chemistry in Soils Observed by Synchrotron-Based Spectroscopy

Lehmann

Solomon

2010

Developments in Soil Science

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Section: Resolving Key Questions In Soil Biogeochemistrymentioning

confidence: 99%

Organic Carbon Chemistry in Soils Observed by Synchrotron-Based Spectroscopy

Lehmann

Solomon

2010

Developments in Soil Science

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“…0.3-3.7 mmol C L -1 (Pearson 1999;Courdouan et al 2007;Eichinger et al 2011). According to previous studies made on clay aqueous extracts (Courdouan et al 2007;Eichinger et al 2011), the low molecular weight (and thus easily biodegradable) organic fraction found in Opalinus Clay water contains highly variable concentrations of acetate (2-31% of DOC), formate (0.2-4% of DOC) and other small organic compounds. In contrast to these studies, no detectable concentrations of acetate, formate or oxalate could be found in the BN interval solutions after the saturation and equilibration period (Table 1) nor before the start of the injection tests discussed here.…”

Section: Chemical Composition Of Solution In the Bn Boreholementioning

confidence: 99%

Impact of the electron donor on in situ microbial nitrate reduction in Opalinus Clay: results from the Mont Terri rock laboratory (Switzerland)

et al. 2017

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At the Mont Terri rock laboratory (Switzerland), an in situ experiment is being carried out to examine the fate of nitrate leaching from nitrate-containing bituminized radioactive waste, in a clay host rock for geological disposal. Such a release of nitrate may cause a geochemical perturbation of the clay, possibly affecting some of the favorable characteristics of the host rock. In this in situ experiment, combined transport and reactivity of nitrate is studied inside anoxic and water-saturated chambers in a borehole in the Opalinus Clay. Continuous circulation of the solution from the borehole to the surface equipment allows a regular sampling and online monitoring of its chemical composition. In this paper, in situ microbial nitrate reduction in the Opalinus Clay is discussed, in the presence or absence of additional electron donors relevant for the disposal concept and likely to be released from nitrate-containing bituminized radioactive waste: acetate (simulating bitumen degradation products) and H 2 (originating from radiolysis and corrosion in the repository). The results of these tests indicate that-in case microorganisms would be active in the repository or the surrounding clay-microbial nitrate reduction can occur using electron donors naturally present in the clay (e.g. pyrite, dissolved organic matter). Nevertheless, non-reactive transport of nitrate in the clay is expected to be the main process. In contrast, when easily oxidizable electron donors would be available (e.g. acetate and H 2 ), the microbial activity will be strongly stimulated. Both in the presence of H 2 and acetate, nitrite and nitrogenous gases are predominantly produced, although some ammonium can also be formed when H 2 is present. The reduction of nitrate in the clay could have an impact on the redox conditions in the pore-water and might also lead to a gas-related perturbation of the host rock, depending on the electron donor used during denitrification.

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“…Improved analytical capabilities revealed in later experiments that approximately half of the dissolved TOC is present in form of carboxylic acids like acetate, formate, and lactate. These concentrations are decreasing gradually with time below those seen in aqueous extracts back-calculated to pore water concentration but remain higher than measured from some boreholes used for longterm sampling of pore water [21]. The exact nature and mechanism of the production and release of carboxylic acids in these rocks and the relationship to the solid organic matter are not yet well understood.…”

Section: Anion Exclusion Effect and Controls On Pore Watermentioning

confidence: 92%

Advective Displacement Method for the Characterisation of Pore Water Chemistry and Transport Properties in Claystone

Mäder

2018

Geofluids

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The advective displacement method applies large hydraulic gradients to a confined rock core sample to yield small aliquots of the preserved in situ pore water, applicable to aquitard rocks with hydraulic conductivities as low as 10 −14 m/s. Examples from argillaceous rocks indicate that only minor artefacts are induced and that analytical methods optimized for small aliquots provide a comprehensive chemical and isotopic characterisation. Multicomponent transport properties are derived from extending experimental time and using a traced artificial pore water for injection. Examples include quantification of the anion exclusion effect that can even resolve a small difference between transport properties for chloride and bromide in claystone. Controls by mineral saturation and cation exchange processes are also constrained by data from this approach. Technical details are provided for construction, material selection, components, sensors, and analytical issues.

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Characterization of dissolved organic matter in anoxic rock extracts and in situ pore water of the Opalinus Clay

Cited by 73 publications

References 23 publications

Organic Carbon Chemistry in Soils Observed by Synchrotron-Based Spectroscopy

Organic Carbon Chemistry in Soils Observed by Synchrotron-Based Spectroscopy

Impact of the electron donor on in situ microbial nitrate reduction in Opalinus Clay: results from the Mont Terri rock laboratory (Switzerland)

Advective Displacement Method for the Characterisation of Pore Water Chemistry and Transport Properties in Claystone

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