Evaluación de los efectos adversos en lixiviados de sedimentos marinos expuestos a fugas asociadas con la inyección y almacenamiento de co2

Résumé

Storing CO2 at sub-seabed geological structures at great water depth has been considered as a mitigation option to reduce the emissions of greenhouse gases. However, there are doubts related to the effectiveness of this technique: especially in terms of environmental impact, because it has not been possible to ensure 100 % confinement of the stored gas during the estimated storage time. Therefore, it is important to evaluate the effects of potential CO2 leakage on the marine environment. This thesis aims to evaluate the effects associated with acidification of marine sediments by potential CO2 leakage in CS-SSGS (CO2 Sequestration in Sub-seabed Geological Structures) systems. To this end, different toxicity tests have been designed and optimized to employ a battery of tests, to simulate the effects of CO2 leakage under laboratory conditions. It was intended to determine the acute effects on the exposed organisms, as well as the effects of CO2 on the behavior of the metals present on the sediments. The presented work was divided into several approaches through the subjection of marine organisms to various exposure phases; such as sea water, sediment-water interface, and exposure of organisms to sediment elutriates, all of which were carried out under atmospheric pressure conditions. Finally, marine sediment exposure to controlled flow of CO2 under 30 atmospheres pressure conditions were conducted. Results determined that leakages of CO2 in marine environments may cause adverse effects on the biota exposed, and would lead to changes in the behavior of metals present in the sediments. Hence, physical and chemical characterization of sediments, together with toxicity tests, would be helpful tools to establish the risk associated with marine acidification processes by increasing the concentration of CO2. The results confirm that the use of these type of approaches (toxicity tests, determination of pollution levels, mobility of metals, etc.) are required to improve the environmental risk assessments (necessary for an appropriate and safe development of the Carbon Capture and Storage (CCS) activities.