Investigations on the complexation behaviour of humic acids and their influence on the migration of radioactive and non-radioactive substances under conditions close to nature

For the long-term safety assessment of waste repositories, detailed information about the geochemical behaviour of radioactive and toxic metal ions under environmental conditions (geologic matrix and aquifer systems) is necessary. It includes the knowledge of the mechanism of relevant geochemical reactions, as well as thermodynamic and kinetic data. The basic approach of the present is to provide fundamental process understanding. It differs from previous activities by introducing new reference humic substances and new techniques, and to extend its scope by focusing on ternary systems. Along these lines it encompassed the synthesis and characterisation of humic acids with distinct redox functionalities, complexation studies of metal ions (Cu(II), Zn(II), Cd(II), Pb(II), La(III), Th(IV), U(IV,VI), Np(IV,V), Pu(III-VI)), the role of phenolic OH groups in the complexation reaction, EXAFS studies on different metal humates (Th(IV), Np(IV), Np(V), Pu(III)), sorption studies of metal ions onto quartz sand and other mineral surfaces in the presence and absence of humic acid, and migration experiments with metal ions. As new techniques capillary electrophoresis (CE) coupled to ICP-MS and the Wageningen-Donnan-Membrane-Technique (WDMT) have been introduced, optimised and applied for different studies. (orig.)SIGLEAvailable from TIB Hannover: ZA 5141(6999) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Wirtschaft und Arbeit (BMWA), Berlin (Germany)DEGerman