Geochemical characterization of organic ligands for copper(II) in different molecular size fractions in Lake Biwa, Japan

In a previous study, we reported the isolation of organic ligands for coppe r(II), their mass distribution and fluorescence properties in different mol ecular size fractions of the waters in Lake Biwa by immobilized metal ion a ffinity chromatography (IMAC) and three dimensional excitation/emission mat rix spectroscopy (3DEEM) (Wu, F., Tanoue, E., 2001. Molecular mass distribu tions and fluorescence characteristics of organic ligands for copper (II) i n Lake Biwa, Japan. Org. Geochem. 32, 11-20). In this continuous study, geo chemical properties of these isolated ligand fractions were characterized i n terms of binding complexation. functional groups and amino acid compositi on. The results show that two ligand classes (L-1 and L-2) were recovered f rom all molecular size ligand fractions, L, with a conditional stability co nstant (LogK'(CuL)) of 7.82-9.56, and L-2 with a LogK'(CuL) value of 7.05-8 .78. The stronger ligands with protein-like fluorescence were of recent bio genic origin, and the weaker ligands with humic-like fluorescence were rela ted to refractory humic substances. Functional groups responsible for the f luorescence in the ligand fractions are also discussed. The results present ed here would have significance for understanding the nature of natural org anic ligands and their biogeochemical role in aquatic systems. (C) 2001 Els evier Science Ltd. All rights reserved.