Conditional stability constant, trace metal

Ruzic [278 ] considered the theoretical aspects of the direct titration of copper in seawaters and the information this technique provides regarding copper speciation. The method is based on a graph of the ratio between the free and bound metal concentration versus the free metal concentration. The application of this method, which is based on a 1 1 complex formation model, is discussed with respect to trace metal speciation in natural waters. Procedures for interpretation of experimental results are proposed for those cases in which two types of complexes with different conditional stability constants are formed, or om which the metal is adsorbed on colloidal particles. The advantages of the method in comparison with earlier methods are presented theoretically and illustrated with some experiments on copper (II) in seawater. The limitations of the method are also discussed. 

Kramer, C.3.M. and Duinker, 3.C., 1984a. Complexation capacity and conditional stability constants for copper of sea- and estuarine waters, sediment extracts and colloids. In C.3.M. Kramer and 3.C. Duinker (eds), Complexation of Trace Metals in Natural Waters. Nijhoff/3unk Publ., the Hague, pp. 217-228. 

Alberts, J. J. and Giesy J.P., Conditional stability constants of trace metals and naturally occurring humic materials Application in equilibrium models and verification with field data. In Aquatic and Terrestrial Humic Materials, R.F. Christman and E.T. Gjessing (Eds.),Ann Arbor Science Publishers, Ann Arbor, Ml, 1983, pp538. 

Glaus, M. A., Hummel, W., and Van Loon, L. R. (2000). Trace metal-humate interactions., I. Experimental determination of conditional stability constants. Appl. Geochem. 15, 953-973. 

Several imperfections remain, both in our understanding of the chemistry of trace metals in natural waters and in the sophistication of our experimental techniques, that prevent an exact determination of the thermodynamically available fraction ( oC pb , equation 4) and the electrochemically available fraction (Ij /I j, equation 11). The stability constants used in calculating the individual o"-values (equation 2) are subject to considerable uncertainty ( 2, 21, 42) and the conventional fj -values used in their adjustment to sea water conditions are based on a multiplicity of conventions. For many complexes that may be important in natural samples the stability constants are unknown and, frequently, the ligands have not been identified. 

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