title: An Isotopic Exchange Kinetic Model to Assess the Speciation of Metal Available Pool in Soil: The Case of Nickel.
abstract: In this study an innovative approach is proposed to predict the relative contribution of each mineral phase to the total metal availability in soils, which, in other words, could be called the available metal fractionation. Through the use of isotopic exchange kinetics (IEK) performed on typical Ni bearing phases (i.e., two types of serpentines, chlorite, smectite, goethite, and hematite) the isotopic exchange and metal-solid interaction processes are connected, considering both the thermodynamic and kinetic aspects. Results of Ni IEK experiments on mineral phases are fitted with a pseudo-first order kinetic model. For each Ni bearing phase, this allows to (i) determine the number and size of exchangeable pools (ENi(i)), (ii) assess their corresponding kinetic constants (k(i)), and (iii) discuss the mechanism of Ni isotopic exchange at mineral surfaces. It is shown that all the phases investigated, with the only exception of hematite, present at least two distinct reactive pools with significantly different k(i)values. Results suggest also that metal involved in outer-sphere complexes would display isotopic exchange between 100 and 1000 times faster than metal involved in inner-sphere complexes, and that the presence of high and low affinity sites may influence the rate of isotopic exchange up to 1 order of magnitude. Moreover, the method developed represents a tool to predict and estimate Ni mobility and availability in natural soil samples on the basis of soil mineral composition, providing information barely obtained with other techniques.
authors: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, UMR 7154, CNRS, F-75005 Paris, France.|Univeristà degli Studi di Torino ,Via Pietro Giuria 5, 10125 Torino, Italy.
authors: I O
authors: IO
authors: Zelano
authors: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, UMR 7154, CNRS, F-75005 Paris, France.
authors: Y
authors: Y
authors: Sivry
authors: UMR 8148 GEOPS, Univ. Paris Sud-CNRS-Université Paris Saclay, 91405 Orsay Cedex, France.
authors: C
authors: C
authors: Quantin
authors: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, UMR 7154, CNRS, F-75005 Paris, France.
authors: A
authors: A
authors: Gélabert
authors: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, UMR 7154, CNRS, F-75005 Paris, France.
authors: A
authors: A
authors: Maury
authors: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, UMR 7154, CNRS, F-75005 Paris, France.
authors: K
authors: K
authors: Phalyvong
authors: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, UMR 7154, CNRS, F-75005 Paris, France.
authors: M F
authors: MF
authors: Benedetti
mesh_terms: D007700:Kinetics; D008670:Metals; D009532:Nickel; D012987:Soil; D012989:Soil Pollutants
chemical_list: D008670:Metals; D012987:Soil; D012989:Soil Pollutants; D009532:Nickel