A semi-empirical thermodynamic model was applied to estimate the apparent formation constants of actinide ions, i.e., Th(IV), Pu(IV) and Np(V), with humic substances (HSs), including humic and fulvic acids, over a wide range of solution conditions, i.e., pH, ionic strength, and HS and metal concentrations. The hypothetical HSs consist of humic and fulvic acids with nine types of simple organic ligands, which include aromatic and aliphatic carboxyl groups and phenol groups, as binding sites. The abundance of each binding site in the hypothetical HSs was determined via a fitting analysis using an aciddissociation dataset for several HSs. To determine the apparent formation constant of a given metal ion with HSs, 54 specific binding sites were considered, including nine monodentate sites (1 : 1 metal/ligand complexes) and 45 bidentate sites (1 : 2 metal/ligand complexes). The formation constant of each monodentate binding was determined from the experimental data, while those of the bidentate bindings were determined by considering two monodentate bindings and the chelating effect, for which one of the adjustable parameters was introduced in the model. Introduction of the other parameter, which is related to the fraction of monodentate to bidentate sites (i.e., the heterogeneity), afforded the parameter values with good correlation with the apparent formation constant data. The present model with adjusted parameter values well reproduced the experimental apparent complex formation constants for actinide ion interaction with HSs in a wide range of solution conditions except for those obtained at trace concentrations.

Characteristics (structure) of global warming issues in developing countries are not identical with those in developed countries. Accordingly, response strategy for global warming to be taken by developing countries must be different from those to be taken by developed countries. This report, as a case study, presents views on structure of global warming issues and response strategy to be taken in Indonesia.

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