1 year psot-doctoral position_ Mineralogical investigations on steel-river sediments_ LIEC_Vandoeuvre-les-Nancy - LIEC, CNRS-Université de Lorraine, Vandoeuvre-les-Nancy, France

River sediments are recognized as reservoirs of multiple pollutants, either chemical (nitrates,
pesticides, medical drugs, metals...) or microbiological (virus, bacteria, parasites). Indeed, surface
waters are often the common receptacle of anthropogenic pollutants from diverse origins, which, once
combined to suspended mater, settle to enrich the sediment compartment. During flood events, the
remobilization of these sediments associated to the inflow sediments will impact water quality, (i)
physically by the redistribution of aggregates between the dissolved, colloidal and particulate
compartments (ii) chemically and biologically by the modification of the speciation of micropollutants
and the selective release of pathogens. Actually, the fate of the settled materials in the sediments and
the dynamics of their re-mobilization need to be better understood for improving the management of
our water resources in terms of quality and downstream treatments for the production of drinking
water. Furthermore, it was demonstrated that about 40% of the annual transport of trace metals
occurred during the 10% highest flow days.
In the research project related to this postdoctoral position (ANR France-Luxembourg MOBISED,
http://mobised.liec.univ-lorraine.fr), the stock of contaminants in sediment profiles from the Orne River
(Moselle watershed, Lorraine, France) was investigated, and sediment deposit in the front of a dam
was showing particularly high contents of “trace metallic elements”, greatly higher than in other
sediment profiles of the same river. Spatial distribution of elements and mineralogy of sediments were
investigated using a combination of analytical techniques (XRD, FTIR, electron microscopies, X-ray
absorption spectroscopy). In order to evidence the nature of interactions between micro-pollutants and
sediment constituents, molecular methods were used to study the chemical speciation of trace
First results on the sediments collected in the Orne River showed mineralogical modifications with
depth, and in particular the formation of Fe enriched phyllosilicates and the formation of polymetallic
sulfides. Zn sulfides, certainly due to the microbial activity within the sediment matrix are constituted of
nanometric entities, are amorphous and could not be evidenced though classical XRD. Those nanosulfides
are however the main Zn scavengers in the sediments.
The first objective will be to quantify the different iron-bearing phases in order to follow the
weathering of iron oxides introduced in the water system during the steel making activity period. The
various iron bearing phases could be quantified combining different sets of data including XRD
patterns and X-ray absorption spectra collected at Fe K-edge. From XRD patterns, the quantification
of mineralogical phases will be performed on the basis of the Rietveld refinement method, which
consists in the comparison of experimental and calculated (or theoretical) patterns, taking into account
the structural data of each mineralogical phase occurring in the sample. The specific case of clay
minerals, described as disordered stacks of layers, will be undertaken with a recent methodology
developed by the team of R Kleeberg.
Spectroscopy data will be analysed using different methods, (1) theoretical modelling or layer by
layer method, (2) standard procedure by principal component analysis and linear combination fitting
using in-house reference spectra and (3) multivariate analysis or MCR. The candidate will work on
previously collected data and will also be involved in the acquisition of complementary data (XRD,
synchrotron sessions in autumn 2017).
A second objective will be to conceptualize and build sediment resuspension experiments in
controlled conditions. Those experiments should help us to evidence the particle remobilization as a
function of experiment duration and physical constraints. Beside the quantification of particle
resuspension, the distribution of elements in the particle, colloidal and dissolved compartments should
be monitored.
-XRD, X-ray absorption spectroscopy (bulk and micro-beam experiments), TEM (EDXS, SAED), SEM
-PCA, MCR, Rietveld refinement, Theoretical modelling of X-ray absorption spectra (with software
based on FEFF code)
• Application deadline: December 1st.
• Audition of candidates: December 2016-Januray 2017
• Recruitment: from February 1st 2017

Date de publication :  6 Novembre 2016
Lieu :  LIEC, CNRS-Université de Lorraine, Vandoeuvre-les-Nancy, France
Document : 
Postdoc MOBISED_region.pdf

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