CO2 geological storage safety assessment: methodological developments

International audienceCarbon dioxide capture and geological storage is seen as a promising technology to mitigate greenhouse gas atmospheric emissions. Its wide-scale implementation necessitates demonstrating its safety for humans and the environment. We have developed a generic approach to provide references for safety assessment of CO2 storage. It is composed of a series of simple tools for identifying risk scenarios, modelling risk events and exposure. It incorporates a rigorous management of uncertainty, distinguishing between variability and knowledge incompleteness. We applied this approach on a case study in the Paris Basin. This demonstrates how it delivers conditions mixing qualitative and quantitative elements for guaranteeing safety. This approach is flexible; it can be used for various sites and with various amounts of data. It can be carried out in a time-efficient manner at various stages of a project. In particular, it provides an operator or an authority with safety indicators in an early phase or for reviewing a risk assessment. Though not a complete risk assessment workflow, it thus partly compensates for the current lack of commonly acknowledged assessment methods or safety standards for CO2 geological storage

Assessment of CO2 health risk in indoor air following a leakage reaching unsaturated zone: results from the first representative scale experiment

International audienceLeakage of CO2 from geological reservoirs is one of the most fearsome unexpected scenarios for CO2 storage activities. If a leakage reaches the ground level, exposure to high CO2 concentrations is more likely to occur in low ventilated spaces (pit dug in the ground, basement, building) where CO2 could accumulate to high concentrations. Significant literature and models about indoor exposure resulting from intrusion of soils gases in building are available in several domains (e.g., contaminated soils, radon, etc.). However, there is no guarantee that those approaches are appropriate for the assessment of consequences of CO2 leakage due the specificity of CO2 and due to the singularities of the source in case of leakage from anthropic reservoirs. Furthermore, another singularity compared to conventional approaches is that the risk due to CO2 exposure should be evaluated considering acute concentrations rather than long term exposure to low concentrations. Thus, a specific approach is needed to enable a quantitative assessment of the risk for health and living in indoor environment in case of leakage from a reservoir reaching the unsaturated zone below the buildings. We present the results of the IMPACT-CO2 project that aims at understanding the possible migration of CO2 to indoor environment and to develop an approach to evaluate the risks. The approach is based on modelling and experiments at laboratory scale and at field representative scale. The aim of the experiment is to capture the main phenomena that control the migration of CO2 through unsaturated zone, and its intrusion and accumulation in buildings. The experimental results will also enable numerical confrontation with tools used for risk assessment. Experiments at representative scale (Figure 1) are performed on the PISCO2 platform (Ponferrada, Spain) specifically instrumented and designed for understanding the impacts of CO2 migration towards the soil surface. The experiment is composed of a 2.2 m deep basin filled with sand upon which a specifically designed cylindrical device representing the indoor condition of a building (with controlled depressurization and ventilation) is set up. The device includes a calibrated interface that represents a cracked slab of a building. The injection of CO2 is performed at the bottom of the basin with a flow rate in the range of hundreds of g/d/m². The first results show that the presence of a building influences significantly the transport of CO2 in the surrounding soil leading to two competing phenomena: 1) seepage in the atmosphere mainly controlled by diffusion gradient and 2) advective/diffusive flux entering the building due to the depressurization. Models have been established to quantitatively assess the proportion of CO

Assessment of CO2 Health Risk in Indoor Air Following a Leakage from a Geological Storage: Results from the First Representative Scale Experiment

If a leakage of CO2 out of a geological reservoir were to happen and to reach the vadose zone below a building, CO2 could migrate through the vadose and the building's slab and accumulate in the building, leading to possible acute risk for the inhabitants. A representative-scale experiment, including a prototype for a building, was developed to better understand and quantify this possible risk. It brought fruitful directions for further modeling work, since unexplained CO2 peaks were observed in the prototype. Numerical simulations were carried out to address the variability of CO2 concentrations considering the influence of soil and building properties as well as meteorological conditions, with promising results for risk analysis

Should I trust you? Learning and memory of social interactions in dementia

Social relevance has an enhancing effect on learning and subsequent memory retrieval. The ability to learn from and remember social interactions may impact on susceptibility to financial exploitation, which is elevated in individuals with dementia. The current study aimed to investigate learning and memory of social interactions, the relationship between performance and financial vulnerability and the neural substrates underpinning performance in 14 Alzheimer's disease (AD) and 20 behavioural-variant frontotemporal dementia (bvFTD) patients and 20 age-matched healthy controls. On a “trust game” task, participants invested virtual money with counterparts who acted either in a trustworthy or untrustworthy manner over repeated interactions. A non-social “lottery” condition was also included. Participants’ learning of trust/distrust responses and subsequent memory for the counterparts and nature of the interactions was assessed. Carer-rated profiles of financial vulnerability were also collected. Relative to controls, both patient groups showed attenuated learning of trust/distrust responses, and lower overall memory for social interactions. Despite poor learning performance, both AD and bvFTD patients showed better memory of social compared to non-social interactions. Importantly, better memory for social interactions was associated with lower financial vulnerability in AD, but not bvFTD. Learning and memory of social interactions was associated with medial temporal and temporoparietal atrophy in AD, whereas a wider network of frontostriatal, insular, fusiform and medial temporal regions was implicated in bvFTD. Our findings suggest that although social relevance influences memory to an extent in both AD and bvFTD, this is associated with vulnerability to financial exploitation in AD only, and is underpinned by changes to different neural substrates. Theoretically, these findings provide novel insights into potential mechanisms that give rise to vulnerability in people with dementia, and open avenues for possible interventions

The self-reference effect in dementia: Differential involvement of cortical midline structures in Alzheimer’s disease and behavioural-variant frontotemporal dementia

Encoding information in reference to the self enhances subsequent memory for the source of this information. In healthy adults, self-referential processing has been proposed to be mediated by the cortical midline structures (CMS), with functional differentiation between anterior-ventral, anterior-dorsal and posterior regions. While both Alzheimer’s disease (AD) and behavioural-variant frontotemporal dementia (bvFTD) patients show source memory impairment, it remains unclear whether they show a typical memory advantage for self-referenced materials. We also sought to identify the neural correlates of this so-called ‘self-reference effect’ (SRE) in these patient groups. The SRE paradigm was tested in AD (n=16) and bvFTD (n=22) patients and age-matched healthy controls (n=17). In this task, participants studied pictures of common objects paired with one of two background scenes (sources) under self-reference or other-reference encoding instructions, followed by an item and source recognition memory test. Voxel-based morphometry was used to investigate correlations between SRE measures and regions of grey matter atrophy in the CMS. The behavioural results indicated that self-referential encoding did not ameliorate the significant source memory impairments in AD and bvFTD patients. Furthermore, the reduced benefit of self-referential relative to other-referential encoding was not related to general episodic memory deficits. Our imaging findings revealed that reductions in the SRE were associated with atrophy in the anterior-dorsal CMS across both patient groups, with additional involvement of the posterior CMS in AD and anterior-ventral CMS in bvFTD. These findings suggest that although the SRE is comparably reduced in AD and bvFTD, this arises due to impairments in different subcomponents of self-referential processing

Synthèse sur les impacts potentiels du stockage géologique du CO 2 sur les ressources en eau souterraines

International audienceAfin de réduire les émissions atmosphériques de CO 2 provenant des activités humaines, des stratégies novatrices de stockage doivent être appliquées au dioxyde de carbone (CO 2 ) produit par la combustion de combustibles fossiles. Parmi les techniques de stockage actuellement proposées, le captage, le transport et le stockage du CO 2 sont proposés. Le stockage géologique du CO 2 consiste à injecter du CO 2 dans les formations géologiques profondes, par exemple dans les réservoirs de pétrole et de gaz épuisés, les formations salines profondes et des veines de charbon inexploitables. L‟objectif est de stocker de grande quantité de CO 2 et de le maintenir isolé de l‟atmosphère durablement.La technologie du captage et stockage de CO 2 (CSC) se doit également d‟avoir un impact minimal et acceptable sur la sécurité et la santé humaine, les ressources du sous-sol dont les eaux et sur l‟environnement. En France, le stockage principalement envisagé dans des formations aquifères profondes dont les eaux sont impropres à leur utilisation par l‟homme. Un stockage sûr et permanent est donc en mesure de respecter les conditions de sécurité pour la santé humaine et l‟environnement. Il convient néanmoins de s‟assurer que les futurs sites de stockage soient suffisamment bien caractérisés et surveillés pour éviter toutes défaillances ou impacts susceptibles notamment d‟altérer les ressources en eauxsouterraines.Ce rapport a pour objectif de décrire les impacts du stockage du CO2 sur les eaux souterraines et se focalise sur le stockage en aquifère salin profond