MINERALS, MONITORS AND ACTORS OF OUR ENVIRONMENT

The gap between Mineralogy, Geochemistry and Environmental sciences has been progressively filled during recent decades. Minerals are now considered with their structural defects and impurities, surface reactivity and interactions with the biogeosphere. In addition, molecular scale observations provide a continuous monitoring of the elements from speciation in solutions, to trapping at the bio/geo interfaces and final insertion in mineral lattices and nanophases. Finally, there is a nice balance between laboratory experiments on model systems and observation of important environmental systems. Major societal implications result from these observations, either for advising long-term decisions such as nuclear waste management, or for understanding the impacts of human activities on our environment, such as soil contamination by heavy metals. Such concerns are expected to increase in the future, together with higher needs for energy and stricter policies concerning contaminants. The first part of the talk will be devoted to decrypting the message given by radiation-induced defects in clay minerals. The high specific area of clays makes them sensitive to ground-level radiation doses. By an adequate experimental calibration, it is possible to trace the past transfer of radionuclides in the geosphere, a parameter of major importance during the investigation of natural analogues of geologic repositories for nuclear wastes. The second part will show how the models developed on model systems help in understanding how natural and anthropized systems are contaminated by heavy elements such as lead, zinc or arsenic. Recent developments take into account the influence of the activity on element speciation, e.g. through the biologicallly-assisted formation of iron oxides, which are efficient scavengers of contaminants.