中法核工程与技术学院核声论坛（总第156期）

报告人简介About the speaker：

Christophe Den Auwer is the director of Academy Space Environment Risk and Resilience, the ICN (Institut de Chimie de Nice) deputy director in Université Côte d'Azur. His research interests cover environmental and human radiochemistry and are dedicated at the fate and impact of radionuclides on the hydrosphere, biotope and human. The approach consists in combining analytical and molecular chemistry for a comprehensive description of the transfer processes, accumulation and internalization of radioisotopes including human nuclear toxicology. The core of the research is structured around 3 main topics: (i) Transfer, reactivity and localization of radionuclides in the environment, (ii) Chemistry and reactivity of radionuclides in living organisms, including human, (iii) Spectroscopy of the actinides. Regarding the human compartment, the main objective is to characterize the interaction between radioelements and biomolecules, combining analytical techniques such as radiometry and spectroscopic tools among which X-ray spectroscopy plays a central role.

报告摘要Abstract:

The mechanisms of dissemination of radionuclides resulting from an accidental release in the environment, in particular in the hydrosphere, is a scientific and societal issue. Hence, the need for managing the risk, for controlling the environmental fate and transport of radionuclides, and for preventing human exposure through the food chain is essential. Among the different hydrosphere compartments, seawater represents the largest proportion of water on Earth as it covers by itself about 71% of the Earth’s surface. It is therefore crucial to understand the transfer and accumulation mechanisms of radionuclides in the marine environment and to attempt to perform direct speciation analysis in seawater. But speciation is poorly described in marine ecosystems because of its complexity and large dilution factors that preclude direct investigation. Therefore, it is required to shift from a purely descriptive radioecological approach to a mechanistic approach and this can be performed with the use of speciation tools and model (eco)systems.

Our group has been investigating the speciation and impact of contamination of several actinides (uranium, neptunium, plutonium, americium), fission products (cesium) and activation products (cobalt) [1,2]. We have monitored the uptake mechanisms of those metallic radionuclides, in vivo, with sentinel species like echinoderms and bivalve mollusks [3,4]. After a specific contamination procedure, concentration factors have been measured. And we have combined several spectroscopic techniques mostly based on X ray Absorption Spectroscopy (XAS) in bulk mode and spatially resolved mode (imaging), together with electron microscopy and secondary ions mass spectrometry images to decipher the radionuclide speciation and map its localization. The complexity of the object itself may be viewed as incompatible with the obtention of fundamental speciation data. Nevertheless, the introduction of modern spectroscopic and spectrometric techniques in environmental sciences pushes the limits of detection and supports an argument for integrated methodologies.