Ifsttar PhD subject

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Title : Dynamics of copper in stormwater management : speciation and transfer modeling

Main host Laboratory - Referent Advisor   -

Director of the main host Laboratory   -

PhD Speciality chimie de l’environnement / géochimie

Axis of the performance contract 3 - COP2017 - Planning and protecting regions

Main location Nantes

Doctoral affiliation UNIVERSITE DE NANTES

PhD school EGAAL - Ecologie, Géosciences, Agronomie et Alimentation

Planned PhD supervisor RUBAN Véronique  -    -

Planned financing Contrat doctoral  - Ifsttar

Abstract

In stormwater management, retention and infiltration facilities are commonly used to regulate water flow and reduce pollutant loads in stormwater runoff. However, the effectiveness of these structures in purifying water is often questioned due to variability in metal contaminant concentrations and a low retention of dissolved fractions (<0.45 µm) of these elements. In order to clarify the purification deficits and the potential impact of the discharges in terms of bioavailability, this study aims to investigate hypotheses concerning trace metal transfer in a retention-infiltration basin located in Nantes that receives stormwater runoff from the heavily-trafficked Cheviré bridge (100,000 vehicles per day). By using a fractionation method to examine the physical speciation of elements, this study reveals the existence of a fine particulate fraction that is difficult to settle and mobile (between 0.45 µm and 8 µm), particularly for Cu and Zn. Further investigation shows that up to 50% of the dissolved fraction is bioavailable. The study also reveals that trace metal distribution across different solid phases of sediment varies according to sediment age (degree of maturation), with some metals, including Cu, Zn, and Cd, showing greater remobilization capacity in richer mineral sediment. The fraction extractable with acetic acid was found to contribute significantly to this difference.

Keywords : retention and infiltration pond, urban stormwater runoff, sediments, trace metals, fractionation, lability

Main host Laboratory - Referent Advisor	-
Director of the main host Laboratory	-
PhD Speciality	chimie de l’environnement / géochimie
Axis of the performance contract	3 - COP2017 - Planning and protecting regions
Main location	Nantes
Doctoral affiliation	UNIVERSITE DE NANTES
PhD school	EGAAL - Ecologie, Géosciences, Agronomie et Alimentation
Planned PhD supervisor	RUBAN Véronique - -
Planned financing	Contrat doctoral - Ifsttar
Abstract In stormwater management, retention and infiltration facilities are commonly used to regulate water flow and reduce pollutant loads in stormwater runoff. However, the effectiveness of these structures in purifying water is often questioned due to variability in metal contaminant concentrations and a low retention of dissolved fractions (<0.45 µm) of these elements. In order to clarify the purification deficits and the potential impact of the discharges in terms of bioavailability, this study aims to investigate hypotheses concerning trace metal transfer in a retention-infiltration basin located in Nantes that receives stormwater runoff from the heavily-trafficked Cheviré bridge (100,000 vehicles per day). By using a fractionation method to examine the physical speciation of elements, this study reveals the existence of a fine particulate fraction that is difficult to settle and mobile (between 0.45 µm and 8 µm), particularly for Cu and Zn. Further investigation shows that up to 50% of the dissolved fraction is bioavailable. The study also reveals that trace metal distribution across different solid phases of sediment varies according to sediment age (degree of maturation), with some metals, including Cu, Zn, and Cd, showing greater remobilization capacity in richer mineral sediment. The fraction extractable with acetic acid was found to contribute significantly to this difference.
Keywords :	retention and infiltration pond, urban stormwater runoff, sediments, trace metals, fractionation, lability

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