GEOSCAN, résultats de la recherche


TitreKinetics of trace metal competition in the freshwater environment: some fundamental characteristics
AuteurFasfous, I I; Yapici, T; Murimboh, J; Hassan, N M; Chakrabarti, C L; Back, M H; Lean, D R S; Grégoire, D C
SourceEnvironmental Science & Technology (ES & T) vol. 38, no. 19, 2004 p. 4979-4986,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20080030
ÉditeurAmerican Chemical Society (ACS)
Documentpublication en série
Mediapapier; en ligne; numérique
Sujetsgéochimie du cadmium; géochimie du plomb; géochimie du cuivre; géochimie du zinc; géochimie du cobalt; géochimie du nickel; géochimie du manganèse; géochimie de l'eau; métaux; cobalt; cuivre; nickel; zinc; manganèse; plomb; analyses des éléments en trace; géochimie des éléments en trace; géochimie
Illustrationsanalyses; plots; graphs; tables
ProgrammeCRSNG Conseil de recherches en sciences naturelles et en génie du Canada
Résumé(disponible en anglais seulement)
Freshwaters are recognized as dynamic systems that may be far-removed from equilibrium. A kinetic approach using the competing ligand exchange method with Chelex 100 as the competing ligand and inductively coupled plasma-mass spectrometry to measure the dissociation kinetics was used to investigate the chemical speciation of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) in model solutions of a well-characterized fulvic acid (Laurentian fulvic acid) and a freshwater sample collected from the Grand River (Ontario, Canada). The kinetic distribution of the metal species were quantitatively characterized by their first-order dissociation rate constants. This kinetic speciation approach has the advantage of providing an objective method for estimating the dissociation rate constants without any a priori assumptions about the number of kinetically distinguishable components or the shape of the distribution. Three factors were found to influence the kinetics of trace metal competition in the freshwater environment:? (i) metal-to-ligand ratio, (ii) ionic potential (z2/r), and (iii) ligand field stabilization energy. The results illustrate the importance of considering the valence-shell electron configuration in predicting the kinetics of trace metal competition in the freshwater environment. The markedly slow dissociation kinetics of Ni(II) and Cu(II) species suggest that the usual equilibrium assumption for freshwaters may not be valid. This study has demonstrated the ability of the kinetic model to correctly predict the relative rates of trace metal reactions, indicating that the kinetic model provides a chemically significant description of the kinetic processes in natural waters.