Microbiology of the Deep Subsurface Geosphere and Its Implications for Used Nuclear Fuel Repositories

McKelvie, Jennifer; Korber, Darren R.; Wolfaardt, Gideon

doi:10.1007/978-3-319-28071-4_7

Cited by 4 publications

(7 citation statements)

References 113 publications

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“…Though the presence of lactate and sulfate in studied anoxic microcosms created differential conditions for enrichment of specific physiological groups of bacteria, yet the phylogenetic analysis of recovered 16S rRNA clone libraries can be extrapolated to give a potential picture of the functional repertoire of microorganims that proliferated in the different clay systems. While lactate would not be found in natural bentonites, addition of this easy-to-assimilate substrate to microcosms has the benefit of stimulating the entire bacterial consortium, including sulfide- and acid-producing bacteria that could cause deteriortation of materials in a DGR ( McKelvie et al., 2016 ), making them more assessable for the purposes of the comprehensive microbiological investigation.…”

Section: Discussionmentioning

confidence: 99%

“…That said, the microcosms facilitated the discovery of a diversity of indigenous bacteria present in as-received clays and helped to evaluate their potential behavior within different ecological or technical scenarios ( e.g ., within low clay-swelling pressure, gel-like interfaces that may temporarily exist between bentonite blocks and host rocks containing groundwater or technical fluids). From an EBS perspective, potential energy sources for microbial consortia in clay buffers would primarily consist of radiolytic dihydrogen gas and organic contaminants introduced along with technical fluids during DGR construction and maintenance ( McKelvie et al., 2016 ), as well as anaerobic container corrosion (which produces hydrogen) after conditions in a DGR evolve to become anoxic. Yet, activity of such an adapted, multipotent indigenous bacterial population, even in hospitable water-saturated clay microcosms, would be anticipated to remain largely-constrained.…”

Section: Discussionmentioning

confidence: 99%

“…As genuine bio-catalysts, bacteria are capable of vigorously modifying their environments through their growth and metabolite production. Some of these transformations may cause substantial changes in the structure and stability of certain components of the EBS, with deleterious effects on the overall integrity and functionality of the barrier system ( McKelvie et al., 2016 ). Sulfate-reducing bacteria (SRB) are of particular concern since biogenic sulfide is expected to be a main corrosive agent for copper canisters under anoxic conditions in a DGR (e.g., King, 2009 ).…”

Section: Introductionmentioning

confidence: 99%

“…The suppression of microbial activity in sealing materials surrounding waste containers is predicted to minimize the contribution of microbially-influenced corrosion to the overall corrosion process to acceptable levels ( King, 2009 ). Indigenous microorganisms within deep groundwater and host rock, along with bacteria introduced with fluid seepage during construction and maintenance of a DGR, will be an unavoidable source of microbial contamination in the EBS ( McKelvie et al., 2016 ). In addition, commercially-available bentonites, including Wyoming MX-80 bentonite - the reference clay for DGR concepts in Canada, Sweden and Finland – have been demonstrated to harbour a small set of bacteria ( Haveman et al., 1995 ; Pedersen et al., 2000 ; Stroes-Gascoyne et al., 2006 ).…”

Section: Introductionmentioning

confidence: 99%

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Bacterial diversity and production of sulfide in microcosms containing uncompacted bentonites

Grigoryan

Jalique

Medihala

et al. 2018

Heliyon

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AimsThis study examined the diversity and sulfide-producing activity of microorganisms in microcosms containing commercial clay products (e.g., MX-80, Canaprill and National Standard) similar to materials which are currently considered for use in the design specifications for deep geologic repositories (DGR) for spent nuclear fuel.Methods and resultsIn anoxic microcosms incubated for minimum of 60 days with 10 g l-1 NaCl, sulfide production varied with temperature, electron donor and bentonite type. Maximum specific sulfide production rates of 0.189 d−1, 0.549 d−1 and 0.157 d−1 occurred in lactate-fed MX-80, Canaprill and National Standard microcosms, respectively. In microcosms with 50 g l-1 NaCl, sulfide production was inhibited. Denaturing gradient gel electrophoresis (DGGE) profiling of microcosms revealed the presence of bacterial classes Clostridia, Bacilli, Gammaproteobacteria, Deltaproteobacteria, Actinobacteria, Sphingobacteriia and Erysipelotrichia. Spore-forming and non-spore-forming bacteria were confirmed in microcosms using high-throughput 16S rRNA gene sequencing. Sulfate-reducing bacteria of the genus Desulfosporosinus predominated in MX-80 microcosms; whereas, Desulfotomaculum and Desulfovibrio genera contributed to sulfate-reduction in National Standard and Canaprill microcosms.ConclusionsCommercial clays microcosms harbour a sparse bacterial population dominated by spore-forming microorganisms. Detected sulfate- and sulfur-reducing bacteria presumably contributed to sulfide accumulation in the different microcosm systems.Significance and impact of studyThe use of carbon-supplemented, clay-in-water microcosms offered insights into the bacterial diversity present in as-received clays, along with the types of metabolic and sulfidogenic reactions that might occur in regions of a DGR (e.g., interfaces between the bulk clay and host rock, cracks, fissures, etc.) that fail to attain target parameters necessary to inhibit microbial growth and activity.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Bacterial diversity and production of sulfide in microcosms containing uncompacted bentonites

Grigoryan

Jalique

Medihala

et al. 2018

Heliyon

View full text Add to dashboard Cite

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“…Microbiology within nuclear waste disposal has been a matter of important studies during the last five decades. Biogeochemical effects on the chemistry and the long-term evolution of repository materials as well as on the transport of radionuclides have been extensively studied [60,74,105]. Among other processes mediated by microbes, biodegradation of bituminized waste forms [104] yielding small organic compounds, is a case comparable to the one studied here, involving SPs biodegradation.…”

Section: Microbial Degradationmentioning

confidence: 81%

The role of superplasticizers and their degradation products on radionuclide mobility

García Cobos

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The most widely accepted option for the long-term management of radioactive waste materials considers their disposal in deep underground facilities (examples are Finland, Belgium, France, Sweden, etc.). Such installations should ensure the safety of the waste disposal and minimize possible future external waste perturbation. Concrete and concrete-based materials are widespread in those facilities. Superplasticizers (SPs) are organic polymers used to improve several concrete properties such as workability. The hyperalkaline conditions developed in cementitious environments, can cause chemical transformations of these polymeric materials (degradation, aging, etc.) with the subsequent production of new organic compounds with different chemical properties. Several organic compounds have a high capacity to form stable complexes with some radionuclides of interest from the point of view of radiological and toxicological doses. Therefore, the understanding on the nature and strength of the interactions between radionuclides and organic admixtures present in the concrete formulations (and their degradation products) is of the outmost importance to conduct adequate assessments of the future performance of the disposal facility. Overall the work presented in this thesis tries to discern the effect that polycarboxylic ether-based (PCE) SPs present in the concrete admixtures used in the deep disposal repository may have on radionuclide mobility. To this aim, the stability of PCE towards temperature, radiolysis and hydrolysis degradation processes has been also studied. This provides a test of the integrity of SPs under the expected repository conditions. This work presents a state-of-the-art of the degradation process of SPs and a thermodynamic study on the effect that model compounds, considered as proxy SPs degradation products, have on the chemistry of several radionuclides (Ni, Eu, U). Short-chain organic compounds such as acetate, phthalate, oxalate, phenol, urea, etc., have been confirmed as possible SPs degradation products. Our results indicate that the complexation capacity of the proxy SPs degradation products considered (i.e. acetate, phthalate, phenol and urea) towards Ni Eu and U is almost negligible under alkaline conditions, while relatively important in the near-neutral pH range. In parallel, the experimental degradation of two PCE SPs, one commercial and one synthetic, has been investigated in this work. Our results indicate that the studied SPs remain unaltered when exposed to hydrolysis processes. On another hand, high temperatures or radiation doses cause important changes in the SPs structure, although the main chemical groups remain unaltered. The effect of a PCE SPs, Glenium®27, on nickel hydroxide solubility has been experimentally evaluated. The results indicate that when Glenium®27 is added to water and then mixed with cement, this polymeric material is stabilized (e.g. adsorbed into the cement phases) and not released back to the aqueous solution, with negligible effects on the mobility of nickel. On the contrary, when added directly into synthetic cement porewater samples at high dosages the solubility of nickel hydroxide increases in more than two orders of magnitude. Thermodynamic calculations indicate that the effect of such component on Ni is comparable to the effect exerted by other organic compounds (i.e. isosaccharinate, gluconate, oxalate), thus pointing towards these organics as good surrogates for understanding SPs complexation capacity. L'opció més àmpliament acceptada per a la gestió a llarg termini de residus radioactius considera el seu aïllament en instal·lacions subterrànies profundes (aquesta opció és fermament recolzada per països com Finlàndia, Bèlgica, França o Suècia). Aquestes instal·lacions han d'assegurar la seguretat de la disposició dels residus i minimitzar-ne possibles pertorbacions externes. El formigó és un material àmpliament utilitzat en aquests tipus d’instal·lacions. Els superplastificants (SPs) són polímers orgànics que s'utilitzen per millorar diverses propietats mecàniques del formigó, de manera que és previsible que aquests components estiguin presents en aquests magatzems en quantitats elevades. Les condicions alcalines que es generen en entorns de ciment i formigó poden induir a modificacions químiques dels SPs com ara la seva degradació o envelliment amb la conseqüent formació de noves molècules orgàniques. En general, l’afinitat de les molècules orgàniques amb els radionúclids ha estat àmpliament reconeguda en estudis anteriors. Aquesta gran afinitat pot derivar en un potencial augment del transport de radionúclids en l’entorn del magatzem de residus. Aquesta tesi té com a principal objectiu discernir si la presència de SPs (específicament els de tipus policarboxilat, PCE) en el formigó pot tenir un impacte rellevant en la mobilitat dels radionúclids, i per tant en l’estabilitat de les instal·lacions estudiades. Així mateix, aquesta tesi té com a objectiu donar resposta a l’estabilitat d’aquests polímers envers a canvis de temperatura, a l’impacte de radiació i a la seva capacitat d’hidròlisis, processos força comuns en magatzems de residus nuclears Aquest treball de tesi inclou una àmplia recerca bibliogràfica sobre els possibles processos de degradació dels SPs (temperatura, radiació, hidròlisis i activitat microbiana) i un estudi termodinàmic sobre l’efecte de molècules model (assimilables als productes de degradació dels SPs) en la mobilitat de diferents radionúclids (Ni, Eu i U). Aquest estudi ens fa concloure que els compostos orgànics de cadena curta, com l’acetat, el ftalat, l’oxalat, el fenol o la urea, podrien ser alguns dels principals productes de degradació dels SPs. Els càlculs termodinàmics indiquen que la complexació d’aquests compostos envers els radionúclids estudiats és negligible en condicions alcalines, tot i que en sistemes de pH neutre pot arribar a ser important. Paral·lelament a aquest estudi bibliogràfic, s’ha dut a terme un estudi experimental de degradació de dos SPs de tipus PCE, un comercial i un sintètic. Els resultats obtinguts indiquen que els processos d’hidròlisi no afecten aquests materials. Per altra banda quan aquests materials s’exposen a radiació o a elevades temperatures, poden patir canvis importants a la seva estructura tot i que els grups químics principals sembla que resten inalterats. També s’ha fet un estudi de l’efecte d'un SPs de tipus PCE (Glenium®27) en la solubilitat de l’hidròxid de Ni. Els resultats presentats en aquest treball indiquen que quan aquest SPs s’afegeix a l’aigua que es fa servir per preparar les provetes de formigó, aquest material polimèric s’estabilitza (adsorbint-se sobre el propi ciment) i no es torna a solubilitzar. En aquestes condicions l’efecte sobre la solubilitat del Ni és concloentment irrellevant. En canvi, quan aquest material s’afegeix en quantitats elevades directament a l’aigua sintètica de por de ciment, sense estar en contacte amb ciment, s’observa un important efecte en el comportament del Ni, augmentant la seva solubilitat gairebé dos o tres ordres de magnitud. Els càlculs termodinàmics fets en aquest treball indiquen que l’efecte del SPs sobre el Ni és similar a l’efecte que produeixen altres compostos orgànics (isosacarinat, gluconat, oxalat) sobre el mateix element. Això ens fa concloure que aquests poden ser bons substituts per comprendre la capacitat de complexació dels superplastificacdors

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Differential depth distribution of microbial function and putative symbionts through sediment-hosted aquifers in the deep terrestrial subsurface

et al. 2018

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An enormous diversity of previously unknown bacteria and archaea has been discovered recently, yet their functional capacities and distributions in the terrestrial subsurface remain uncertain. Here, we continually sampled a CO-driven geyser (Colorado Plateau, Utah, USA) over its 5-day eruption cycle to test the hypothesis that stratified, sandstone-hosted aquifers sampled over three phases of the eruption cycle have microbial communities that differ both in membership and function. Genome-resolved metagenomics, single-cell genomics and geochemical analyses confirmed this hypothesis and linked microorganisms to groundwater compositions from different depths. Autotrophic Candidatus "Altiarchaeum sp." and phylogenetically deep-branching nanoarchaea dominate the deepest groundwater. A nanoarchaeon with limited metabolic capacity is inferred to be a potential symbiont of the Ca. "Altiarchaeum". Candidate Phyla Radiation bacteria are also present in the deepest groundwater and they are relatively abundant in water from intermediate depths. During the recovery phase of the geyser, microaerophilic Fe- and S-oxidizers have high in situ genome replication rates. Autotrophic Sulfurimonas sustained by aerobic sulfide oxidation and with the capacity for N fixation dominate the shallow aquifer. Overall, 104 different phylum-level lineages are present in water from these subsurface environments, with uncultivated archaea and bacteria partitioned to the deeper subsurface.

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Microbiology of the Deep Subsurface Geosphere and Its Implications for Used Nuclear Fuel Repositories

Cited by 4 publications

References 113 publications

Bacterial diversity and production of sulfide in microcosms containing uncompacted bentonites

Bacterial diversity and production of sulfide in microcosms containing uncompacted bentonites

The role of superplasticizers and their degradation products on radionuclide mobility

Differential depth distribution of microbial function and putative symbionts through sediment-hosted aquifers in the deep terrestrial subsurface

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