Modelling geochemical and kinetic processes involved in lead (Pb) remobilization during resuspension events of contaminated sediments.

Philippe Ciffroy (1) , Lucie Monnin (2) , Jean-Marie Garnier (2) , Jean-Paul Ambrosi (2) , Olivier Radakovitch (2, 3)

1 EDF R&D - EDF R&D
2 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
3 IRSN/PSE-ENV/SRTE/LRTA - Laboratoire de recherche sur les transferts des radionucléides dans les écosystèmes aquatiques

The objective of this paper is to present a model simulating and predicting the exchange kinetics of lead (Pb) between contaminated sediments and water during resuspension events potentially occurring in reservoirs. We developed an innovative model that combines thermodynamic speciation of particulate surfaces (oxides and Particulate Organic Carbon (POC)), thermodynamic Pb speciation in water, and kinetic modelling of exchanges between free Pb and particulate sites (i.e., dissolution of a carbonate carrier phase, adsorption/coprecipitation and desorption/dissolution to/from oxides, and adsorption and desorption/degradation to/from particulate organic particles). We used results from laboratory resuspension experiments performed on sediments from three contaminated dam reservoirs to calibrate a new chemical speciation model. Uptake and release processes to/from sediments were found to be controlled by at least two successive reactions that are associated with two particulate pools (here oxides and POC). Kinetic adsorption and desorption rates were calibrated for seven experimental conditions. Variability in kinetic rates allowed evaluation of the effect of the solid-to-liquid ratio and sediment origin on exchange kinetics at the water-particle interface. The kinetic release of dissolved Pb by desorption or dissolution from the oxides was reproduced almost identically between the experiments, regardless of the solid-to-liquid ratio or sediment origin. Long-term readsorption on POC sites is more variable, even if ranges of variation in the adsorption and desorption kinetic rates related to POC remain limited, considering that tested sediments vary significantly.

Mots clés: Metal remobilization; Sediment resuspension; Speciation; Kinetics modelling; Dam reservoir

Domaines: Sciences de l'environnement; Autre

Philippe Ciffroy, Lucie Monnin, Jean-Marie Garnier, Jean-Paul Ambrosi, Olivier Radakovitch. Modelling geochemical and kinetic processes involved in lead (Pb) remobilization during resuspension events of contaminated sediments.. Science of the Total Environment, 2019, 679, pp.159-171. ⟨10.1016/j.scitotenv.2019.04.192⟩. ⟨hal-02500144⟩