Un nouvel article qu'on a publié dans Aquatic sciences sur :
Spatial variability in sedimentation rates and artificial radionuclide storage in alluvial banks of the lower Rhône River
Résumé :
This paper analyzes the relationship between bank sediment storage and radionuclide content in six alluvial sites located
in different geomorphic contexts along the lower Rhône River. The 137Cs, 238Pu, 239+240Pu, 241Am and 210Pb
profiles show different patterns, which indicates a differential
storage of contaminated sediment in the banks. Three sites
record historical nuclear releases in the river and give
evidence for long-term retention of particle-reactive long-lived
radionuclides. Two sites record only atmospheric global
fallout. Only one site, connected to the river groundwater, provides
some evidence for desorption of particle-bound contaminants,
with a low and constant 137Cs activity profile. The history
of the releases from the Marcoule spent-fuel reprocessing plant—the main
source of artificial
radioactivity—provides a reliable chronology of the last
50 years. Sediment grain size and bank topography are important factors
in determining where artificial radionuclides are stored,
but these two parameters cannot be used alone to determine variations
in high concentrations of radionuclides. The chronology of
fluvial geomorphic “metamorphosis” during the twentieth Century,
especially after 1960, is also a critical factor affecting
the spatial variability in sedimentation rates and artificial
radionuclide
storage; the timing of channel deepening and bank
sedimentary accretion interfere with the chronology of major floods and
the short period of low discharge during the height of
contamination from nuclear liquid effluents. The reach-scale adjustment
described in this paper can contribute to determining what
the local history may have been. This result has important implications
for river management decisions.
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