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Interactions of
cesium with sediments from Mexican aquatic environments
Anne M. Hansen, Apolinar
Cerezo-Román, Vicente Ortega-Lara
Instituto Mexicano de Technología del Agua, Paseo
Cuauhnahuac 8532, 62550 Jiutepec, Mor., Mexico
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Abstract
Through batch experiments, mathematical and numerical
modeling, the migration behavior of radioactive cesium (Cs) was
evaluated in water-sediment phases from different Mexican continental
aquatic systems and near-coastal marine environments. The objective
of the experiment was to understand and simulate the transport,
accumulation, and remobilization patterns occurring in these systems
as a result of natural and man-made variations in solution chemistry
and solid phase compositions of the sediments. The effects of soluble
ligands on the incorporation of Cs in sediments from the different
study environments were also evaluated. The experimental design
reflected variations of system parameters, such as the type of sediment,
ionic strength, pH, time of contact, and concentrations of different
dissolved ions that either competed with Cs for the same adsorption
sites or formed solution species with the study metal. Time-dependent
and equilibrium constants were obtained for the incorporation of
Cs in sediment samples from the different study environments. Cs
adsorbed as outer sphere complexes and exchanged with other cations
in the clay minerals. Major ion concentrations in solution affected
the distribution of the study metal between the dissolved forms
and those attached to the solid surfaces of the sediments. Cs desorption
was evaluated by varying the pH and adding different concentrations
of EDTA, CO2, or pentavanadate to the experimental systems.
Experimental results were used to calibrate time-dependent and equilibrium
models which in turn were used to describe and quantify the observed
phenomena. The results obtained may help in describing the transport
and distribution of radioactive Cs in natural aquatic environments
and in the rehabilitation of sites that were contaminated by planned
or accidental releases from the atomic energy industry. © 1999
Elsevier Science Ltd and AEHMS. All rights reserved.
Keywords: Radioactive
metals; Adsorption; Incorporation; Surface complexation model; Time-dependent
model
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