France, Strasbourg, Laboratories LIVE et LHYGES (Central Campus of University of Strasbourg).
Doctoral School: "Sciences de la Terre et de l'Environnement" (n° 413).
Affiliation: University of Strasbourg.
Environmental costs of the thesis: the thesis will be integrated into the IDEX Juxta Rhenum
project of the University of Strasbourg (2018-2019) and the Observatoire Homme Milieu
(OHM) Fessenheim (2019-2026; CNRS). It will be able to benefit from financial support from
these research structures.
This project globally aims at reconstructing the spatio-temporal dynamics of sedimentary
deposits in the Upper Rhine and their chemical composition in relation to the industrial,
agricultural and urban evolution of this region, from the 18th century onwards. It thereby focuses
on three main time periods:
1. prior to the engineering works of the Rhine (several centuries);
2. main engineering works during the 19th-20th centuries (e.g. canalization of the river and
3. modern times, encompassing the closure of the nuclear power plant of Fessenheim.
Based on a combination of geomorphological, sedimentological, geochemical and isotopic
tracing approaches, the PhD thesis will contribute to the current efforts to reconstruct the history
of the Upper Rhine socio-ecosystem. The coupling of geochemical analyses of the historical
sediments of the Rhine with thorough geomorphological, sedimentological and
geochronological studies of the paleo-channels, which may have worked as pollutant hotspots,
will be a core topic of this project. This will be achieved by mapping the paleo-channels, dating
their formation and coring the fluvial deposits to investigate their mineralogical and
geochemical characteristics. This interdisciplinary research will also provide major information
to establish the current state of the Fessenheim socio-ecosystem and to assess how the closure
and dismantling of the nuclear power plant will impact it. It should also lead to operational
benefits in terms of river restoration. Finally, this project will contribute developing
transposable methodologies to other fluvial contexts.
The first task of the thesis aims at applying and developing geochemical and isotopic tracing
approaches to characterize the sources of the various chemical flows in water and Rhine
sediments and to uncouple the "natural" flows from anthropogenic-influenced flows
(agricultural, industrial, urban...). Different geochemical tracing tools will be used, depending
on the types of contaminants to be traced. This work will be based on an initial inventory to
define the types of tracers according to the types of pollution/activities (thesis in progress
conducted elsewhere). In its initial phase, the PhD student will focus on metal contamination
originating by industries, river infrastructures, agriculture and/or urban activities.
The second task is to evaluate how the temporal analysis of the signals recorded in the fluvial
landforms and sediments of the Rhine (e.g. palaeochannels by-passed by the Rhine rectification
or other floodplain areas) allows reconstructing the past evolution of these contaminations in
the hydrosystem. This work will be based on geomorphology (diachronic geomatics analysis,
study of longitudinal profiles, LIDAR analysis, etc.) and sedimentology (grain size, etc.) to
draw up a detailed mapping of the Rhine paleo-channels, define the fine chronology of their
implementation and select the most relevant ones to core for their mineralogical and
geochemical analysis. A new geochronological method with high stratigraphical resolution will
be used, in collaboration with the University of Freiburg.