Fixation of radiocaesium traces in a weathering sequence mica -> vermiculite -> hydroxy interlayered vermiculite
(1999) European Journal of Soil Science — Vol. 50, n° 1, p. 107-115 (1999)
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- Radiocaesium fixation in soils is reported to occur on frayed edge sites of micaceous minerals. The weathering of mica in acid soils may therefore influence the Cs+ fixation process and thereby the mobility of the radiopollutant. We produced a laboratory weathering model biotite --> trioctahedral vermiculite --> oxidized vermiculite --> hydroxy interlayered vermiculite (HIV) and quantified the Cs' fixation of each mineral both in a fixed K+-Ca2+ background and in acid conditions. The transformation process was achieved through K depletion by Na-tetraphenylboron, oxidation with Br-2 and Al-intercalation using NaOH and AlCl3. In a constant K+-Ca2+ background, vermiculite fixed 92-95% of the initial Cs-137(+) contamination while biotite and HIV fixed only 18-33%. In acid conditions, the interlayer occupancy by either potassium (biotite) or hydroxy-Al groups (HIV) strongly limited Cs+ fixation to 1-4% of the initial Cs-137(+) contamination. Cs+ fixation occurred on vermiculitic sites associated with micaceous wedge zones. Though both oxidized and trioctahedral vermiculites fixed similar Cs+ amounts in a constant K+-Ca2+ background (92-95%), the oxidized vermiculite retained much more radiocaesium in acid conditions (78-84% against 54-59%), because of its dioctahedral character.
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Maes, E., Delvaux, B., Vielvoye, L., & Stone, W. (1999). Fixation of radiocaesium traces in a weathering sequence mica -> vermiculite -> hydroxy interlayered vermiculite. European Journal of Soil Science, 50(1), 107-115. https://doi.org/10.1046/j.1365-2389.1999.00223.x (Original work published 1999)