Financement : MESRI, ANR
Date de début de thèse : octobre 2020
Mots-clef: nanoparticules, mésocosmes, cellules micro-fluidiques, risque environemental.
The emergence of new technologies (eg biomedicine, micro / nanoelectronics, information and communication technologies) represents an environmental challenge in order to assess the exposure to new pollutants and their potential impacts on ecosystems. This is particularly the case of (nano) energy technologies. The development of renewable energies invites to consider new vulnerabilities, linked in particular to mixed metal oxides, necessary for wind turbines, photovoltaic panels and energy storage devices. The aging of the French nuclear installations will also imply the dismantling of nuclear fusion installations. Certain operations of removing tritiated materials such as stainless steel and cement will generate fine airborne particles, whose ecotoxicology is under studied. Finally, the evolution of nuclear technologies towards fission (ITER) will also generate the emission of fine tungsten particles, the environmental risks of which have been poorly investigated.
The objective of this thesis project is to determine the environmental risks associated to (nano) energy technologies and more especially the release of nano-residues during their life cycle. The work will initially be carried out on nanometric particles emitted during the dismantling, operation, and end of life of energy generation and storage devices. In addition, the complexity and chemical heterogeneity of the nano-residues that will be generated will allow us to assess the issues of multiple contamination or cocktail effects (synergistic or antagonistic effects). At this nanoscale, the increased surface reactivity and the large specific surface area imply new behaviors of these nanometric residues in the environment. In addition, due to their mode of dispersion, the level of environmental exposure to nanoparticles is found to be higher than larger objects.
The work will be carried out at two complementary scales : (i) the scale of aquatic mesocosms in order to assess the envrironmental risks related to nano-residues (exposure x impact) on aquatic ecosystems. Mesocosms are experimental devices designed to simulate ecosystems and are a valuable tool for monitoring the exposure during eco-toxicological testing. In this study, we opted for modular mesocosms of small size (60 L). The CEREGE experimental system allows the simultaneous monitoring of a number of parameters (eg, aggregation, settling, mass balance, trophic transfer, biotransformation, oxidative stress, microbial diversity) under ecologically relevant conditions. This experimental device can accommodate several types of ecosystems such as lotic, lentic, estuarine or lagoon environments. We will be able to evaluate (i) the distribution and the bioavailability of nano-residues released in the different mesocosms compartments (water, sediments, living organisms), (ii) the biotransformation (adsorption, oxidation -reduction, production of free radicals) of nano-residues in the compartments with the highest concentrations, (iii) the impacts on exposed organisms (counting of algae and bacteria, development and growth of macro-organisms).
(ii) The scale of microfluidic cells in order to identify the mechanisms of interactions between microorganisms and nanometric residues and to test the mechanistic hypotheses observed in mesocosm experiments. Using microfluidic cells, we will be able to adjust the type and distribution of organisms (microbial community, zoo- and phytoplankton) and pollutants (individual or cocktails) in space and time. We could also consider working with microfluidic devices with specific geometry and materials in order to highlight certain prey-predator relationships.
In both mesocosm and microfluidic cell experiments, nanoscale residues will be characterized using advanced microscopy and spectroscopy techniques. The 2D and 3D imaging techniques based on X-rays implemented at CEREGE make it possible to locate and quantify these residues in organisms, sediments and tissues. The biological effects will be addressed through the use of different biological indices and biomarkers, as well as by the quantification of oxidative stress.