Geochemistry at the nanoscale: chemistry of fluid-mineral interfaces, phytoremediation, and nanotoxocology
Jeudi 31 Mars 2011 à 16h00
Amphithéâtre P015 de l'Ecole PHELMA Polygone
23 rue des martyrs 38000 Grenoble
Par Roland HELLMANN, Géraldine SARRET et Laurent CHARLET,
Institute for Earth Sciences (ISTerre) & Observatory for Earth and Planetary Sciences Grenoble
Présentation Roland HELLMANN- Chemical weathering reactions of rocks at Earth’s surface play a major role in the chemical cycle of elements, and represent one of the major abiotic sinks for atmospheric CO2. Detailed transmission electron microscopy measurements of the surface chemistry of altered laboratory and field-weathered silicate minerals reveal sharp, nanometer-scale chemical concentration jumps that are spatially coincident with sharp crystalline-amorphous interfacial boundaries. These measurements are not in agreement with currently accepted models for chemical weathering, and most importantly, they provide critical evidence for a single, unifying mechanism based on interfacial dissolution-reprecipitation.
- Crop plants are exposed to contaminants present in the soil by root uptake, but also by direct transfer of atmospheric contaminants in the shoots. This latter route of exposure is prevalent in urban or peri-urban environments. The foliar transfer of contaminants is not well understood. We have been studying the fate of Pb-rich micro and nanoparticles in crop plants (lettuce and ray grass). We have shown evidence for the fixation of particles inside the leaf tissue, with the formation of secondary phases. These findings have implications for the evaluation of human and animal exposure.
- In biological fluids, protein and trace elements associate with nanoparticles, and their surface concentration and complex type leads to an in vivo response. This will be important for advancing nanoparticles for imaging, drug delivery, and therapeutic application, and assessing (i) engineered nanoparticle toxicology, as well as (ii) toxics linked to natural nanoparticles, which act via a Trojan horse-type mechanism. We shall discuss low in-vitro toxicity imogolite nanotubes (INT), and the complex they form with essential trace elements (Se) and nanomagnetite, and the flat phyllosilicate associations with prion proteins which may be a Trojan horse entity.
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