title: Kinetic speciation of Co(II), Ni(II), Cu(II), and Zn(II) in model solutions and freshwaters: lability and the d electron configuration.
abstract: The kinetic speciation of Co(II), Ni(II), Cu(II), and Zn(II) in model solutions of a well-characterized fulvic acid (Laurentian fulvic acid), freshwater samples from the Rideau River (Ottawa, Ontario), and freshwater samples from the Sudbury (Ontario) area were investigated by the competing ligand exchange method using Chelex 100 as the competing ligand and by inductively coupled plasma-mass spectrometry to measure the dissociation kinetics. The metal species were quantitatively characterized by the rate coefficient for the first-order dissociation of metal complex to free metal ion. This technique can be applied to almost all elements and represents an important advance in our ability to investigate the kinetic availability of metal species in the freshwater environment. The order of the lability of the metal complexes, Co(II) > Ni(II) > Cu(II) < Zn(II), follows the reverse order of the ligand field stabilization energy with the exception of Cu(II); the behavior of Cu(II) is also due to the Jahn-Teller effect, which shortens the equatorial bonds and lengthens the axial bonds of a tetragonally distorted Cu(II)-L6 complex. This study has demonstrated a relationship between the lability of metal-DOM complexes of the 3d transition metals in freshwaters and their d electron configuration. This is the first time that the importance of the d electron configuration on the lability of metal complexes in the freshwater environment has been demonstrated. The slow complexation kinetics of both Ni(II) and Cu(II) suggestthatthe usual equilibrium assumption for freshwaters may be invalid.
authors.affiliation: Ottawa-Carleton Chemistry Institute, Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6 Canada.
authors.forename: Amina L R
authors.initials: AL
authors.lastname: Sekaly
authors.forename: John
authors.initials: J
authors.lastname: Murimboh
authors.forename: Nouri M
authors.initials: NM
authors.lastname: Hassan
authors.forename: Rupasri
authors.initials: R
authors.lastname: Mandal
authors.forename: Mufida E Ben
authors.initials: ME
authors.lastname: Younes
authors.forename: Chuni L
authors.initials: CL
authors.lastname: Chakrabarti
authors.forename: Margaret H
authors.initials: MH
authors.lastname: Back
authors.forename: D Conrad
authors.initials: DC
authors.lastname: Grégoire
mesh_terms: D001682:Biological Availability; D007700:Kinetics; D013058:Mass Spectrometry; D019216:Metals, Heavy / Q000737:chemistry*; D009930:Organic Chemicals; D014873:Water Pollutants / Q000032:analysis*
chemical_list: D019216:Metals, Heavy; D009930:Organic Chemicals; D014873:Water Pollutants