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12 pagesInternational audienceGeological storage of the greenhouse gas CO2 has the potential to be a widespread and effective option to mitigate climate change. As any industrial activity, CO2 storage may lead to adverse impact on human health and the environment in the case of unexpected leakage from the reservoir. These potential impacts should be considered in a risk assessment process. We present an approach to assess the impacts on human health in case of CO2 leakage emerging in the unsaturated zone under a building. We first focus on the migration of the CO2 in the unsaturated zone and the foundation through numerical simulation with sensitivity analysis. Our results show that the intrusion of CO2 into a building is substantially attenuated by the unsaturated zone and the foundation and may lead only under very specific conditions (very low ventilated parts of buildings, high flow rate and/or building situated very close to a leaking pathway) to hazardous CO2 indoor concentrations. We have then integrated the former results in a global toolbox that provides an efficient and easy-touse tool for decision support, which enables to assess the impacts on human health of CO2 leakage from the reservoir to a building

When capturing CO 2 , the collected gas mixture can vary considerably both qualitatively and quantitatively, based on the CO 2 origin, the capture process and the industrial sector. Co-injected with CO 2 , these impurities might be an issue in case of leakage but may also impact the subsurface storage. Operators of the whole CCS chain are therefore waiting for recommendations in terms of admissible concentrations while regulators are waiting for tools allowing them to formulate these recommendations. The SIGARRR project aims at proposing accurate reactive-transport simulations to model the long-term behavior of CO 2 and its coinjected gases within storage sites focusing on the reactivity with reservoirs and the possible inferences on the environment. The paper presents first numerical results on water-gas equilibriums in agreement with experiments.

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