【实习岗位】斯特拉斯堡大学

【岗位 1】

Topic：开发用于环境中碘原位测量的被动采样器

            Development of passive samplers for in-situ measurement of iodine in the environment

In a context where radioactivity in the environment is a constant concern for society, it is essential to understand the transfer mechanism of radionuclides and to assess their impact on the health of the ecosystem. Particular attention is paid to iodine-129 in the environment released by nuclear activities, due  to  its  relatively  high  fission  yield,  long  half-life  (1.57x107   years),  high  mobility  and  active participation in bio-associated processes. However, I-129 is a difficult-to-measure radionuclide, being a low-energy β- emitter with minute concentrations in the environment. The in-situ quantification of its transfers in soil-water continuums remains a real challenge [1].

Diffusive  Gradients  in  Thin-films  (DGT)  is  an  in-situ  passive  sampler  with  a  widespread  use  in environmental studies [2]. It is based on the accumulation of an analyte onto/into a binding agent that is covered by a diffusive gel aimed to establish a well-defined diffusion layer. This technique would allow to specifically quantify in-situ the labile fraction of iodine, i.e., the fraction of iodine desorbed from the soil into the pore water in a rapid equilibrium. To date, iodide-specific DGT can only be applied to seawater [3], so the aim of this internship is to extend the existing technique to freshwater by developing a new sampler.

The student will be involved in the following tasks:
•   Quantify iodine in water samples collected around the Fessenheim nuclear powerplant
•   Test  the  adsorption  efficiency  of  some  resins  for  iodine  under  different  conditions  using solid/liquid extraction
•   Assembly DGTs from the selected resin, and determine the diffusion coefficient of iodine in the diffusive gel by kinetics experiments
•   In-situ validation of the developed DGT

【岗位 2】

Topic：费森海姆核电站土壤-水连续体中放射性核素与痕量元素的转移

            Transfers of radionuclides and trace metal elements in a soil-water continuum near the Fessenheim nuclear power plant

Radionuclides(RNs) and trace metal elements (TMEs) present in the environment are of great concern for ecosystem health and have gained significant attention from society. Quantifying the levels of RNs/TMEs and understanding their mechanisms of transfers from soils and sediments to stream and ground-waters are crucial for assessing their environmental impact and formulating effective remediation strategies.

Among the various agents involved in the transfers of RNs and TMEs from soils or sediments to stream and ground-waters, natural organic matter resulting from the degradation of plants and other organisms, as well as organic matter of anthropogenic origin (e.g., a variety of organic micro- pollutants released from human activities), are expected to play a key role. Depending on physicochemical conditions, organic matters (OMs) may either favor the retention of RNs and TMEs onto surfaces of the minerals in soils and sediments -due to formation of ternary surface metallo- organic complexes-, or its transport in waters owing to formation of dissolved or colloidal metallo- organic complexes. To this regard, wetlands or floodplains sited at the interface between terrestrial and aquatic (fluvial) media are key geochemical systems. They represent a zone of exchange and they have a high capability to scavenge both OMs and TMEs/RNs. A comprehensive understanding of their complex functioning is thus critically needed, as they are potentially efficient traps of both atmospheric CO2 and organic and metallic pollutants.

Organic matters could thus significantly influence the mobility, bioavailability, and potential impact of contaminants on ecosystems and human health [1, 2]. This internship specifically focuses on studying an ecosystem near the Fessenheim nuclear power plant, which has released RNs/TMEs throughout its 42 years of operation [3]. The primary objective of this internship is to elucidate the relationship existing between the distribution of RNs/TMEs in a soil profile-water system collected in a wetland and the presence/composition of OM present along the soil profile and in the pore water.
 

The student will be involved in the following tasks:
1.Analyze different RNs/ETMs notably uranium, lead, cesium-137, and iodine in a soil core sampleand in percolating waters collected from a wetland sited in the vicinity of the Fessenheim nuclear powerplant and the Old Rhine River,
2.Extract and characterize organic matters in the soil and water samples,
3.Elucidate the impact of organic matters on the soil-water distribution of RNs/TMEs.

院方联系人：康老师

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