Abstract
Radiocaesium ( 137Cs) dispersion and Cs + fixation were studied in the sediments collected from the lagoon systems of “Ria de Aveiro”. The Cs + sorption was tested for the fine mica grains and for the < 2 μm clay fractions extracted from silty clays. The Cs + exchange is found strongly onto mica-rich fractions than smectite-rich fractions. The distribution coefficient increases if the silty material is constituted by rich-mica clay fractions or if the non-clay minerals are removed from the silty-clay material. The samples studied behave as multisite ion exchange, where Cs + engages in ion-exchange reactions with hydrated cations on planar sites on expansible layer silicates. Higher concentrations of the 137Cs were found associated with mica-rich silty clays. The 137Cs ranges from 3.2 to 3.9 Bq kg − 1 in the < 38 μm fractions and from 2.9 to 3.3 Bq kg − 1 in the < 64 μm fractions.
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