Séminaire ISTerre

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Rocks, fluids and microorganisms – The weathering of silicate minerals across scales

samedi 26 octobre 2019 - 11h00

Bastien WILD - Princeton Univ.
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The chemical weathering of minerals is central to several open scientific questions including the long-term fate of atmospheric CO2, the renewal of soil nutrients pools, the release of metal contaminants and the biogeochemical cycling of elements in the critical zone1-3. However, the fundamental processes that control mineral reactivity remain incompletely understood, as illustrated by the long-standing inconsistency between field and laboratory estimates of dissolution kinetics4. This knowledge gap limits our ability to address some of the most pressing societal challenges regarding the safety of deep geological storage of nuclear wastes and CO25,6, the sustainable management of drinking water, forest and land resources, hazards associated to the stability of volcanic edifice and dome structures7 or the development of construction materials with reduced carbon footprints8. This seminar will highlight important rate-limiting processes occurring at the fluid-mineral-microorganism interface, which are generally overlooked by current kinetic models9,10. In particular, textural and structural changes taking place at the reaction interface can control mineral dissolution at several scales, as supported by our recent results from molecular dynamics, advanced electron microscopy and in-situ synchrotron techniques9,11. I will provide new insights from field experiments on the effect of microorganisms and preferential fluid flow pathways in soils on the dissolution rates of minerals. Subtle reciprocal relationships between mineral substrates and associated microbial communities revealed by these experiments will also be described2,12. Overall, this talk will emphasize key differences existing between average "bulk" properties, which are usually recorded in the field or in laboratory setups, and local biogeochemical environments actually driving mineral reactivity in-situ.

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Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères