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DYNAMICS OF RADIONUCLIDE CHEMISTRY IN SOILS AND SEDIMENTS

Objetivo

IN THIS PROPOSAL, A NATURALISTIC APPROACH IS TAKEN IN WHICH THE DYNAMIC INTERACTIONS BETWEEN THE DIFFERENT PROCESS VECTORS ARE PRESERVED, THE EMPHASIS BEING PLACED ON LONG-TERM EFFECTS.
The behaviour of the radionuclides of technetium, europium, strontium, zinc and caesium in soils and sediments have been investigated. The most intense efforts have been directed at the study of the environmental behaviour of radiocaesium, for which a quantitative insight has been gained into the retention mechanistics and for which reliable tools have been developed for predicting its solid liquid distribution behaviour in soils and sediments.

Physicochemical and mechanistic studies have been carried out of the geochemical behaviour of radionuclides in natural systems such as soils and sediments. The chief emphasis of the work is on the geochemical phase associations of radionuclides and dynamic aspects of radionuclide interception and remobilisation processes.
WHEN INTRODUCED INTO THE SOIL AS PERTECHNETATE, TC IS READILY AVAILABLE, AND TAKEN UP BY THE SOIL MICROFLORA AND PLANT ROOTS. UPON WETTING, AND DEPENDING ON TIME AND TEMPERATURE, EH VALUES MAY SHIFT TO LEVELS WHICH ARE CONDUCTIVE IN TC-HUMIC ACID COMPLEXES OR POSSIBLY COMPLEXES WITH EXUDATES OF MICROBIAL ORIGIN.
THE BIOAVAIBILITY OF TC. EITHER COMPLEXED OF PRESENT AS TCO2 CA BE EXPECTED TO BE REDUCED CONSIDERABLY, AS COMPARED TO TCO4. THE FURTHER PATHWAY OF TC TO PLANT ROOTS MAY PROCEED BY EITHER ONE OR BOTH OF THE FOLLOWING PROCESSES:
A) DIRECT UPTAKE IN THE FORM OF LOW M.W. COMPLEXES;
B) LIGAND EXCHANGE OR DISPLACEMENT OF TC FROM SOIL ORGANIC MATTER TO ROOT ORIGINATING EXUDATES IN THE RHIZOSPHERE AND TRANSFER TO THE PLANT ROOT.
THE FOLLOWING LINES OF APPROACH ARE STUDIED:

A. TRANSIENCY OF BIOLOGICAL AND PHYSICO-CHEMICAL PROCESSES.

B. GEOCHEMICAL PHASE ASSOCIATION OF TECHNETIUM.

C. THE STABILITY OF TCO2 ON SOILS IN THE PRESENCE OF ORGANIC MATTER

D. RATE STUDIES OF LIGAND EXCHANGE PROCESSES OF TC.

E. SYNTHESIS, PHYSICO-CHEMICAL CHARACTERIZATION AND THERMODYNAMIC STABILITY OF WELL DEFINED TC-O.M COMPLEXES.

F. RATE STUDIES OF TC UPTAKE IN BIOTA.

Tema(s)

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Régimen de financiación

CSC - Cost-sharing contracts

Coordinador

Katholieke Universiteit Leuven
Aportación de la UE
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Dirección
Naamsestraat 22
3000 Leuven
Bélgica

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