Abstract
226Ra concentrations up to 1000 Bq/kg dry weight have been found in soils on limestone Karst in the Swiss Jura Mountains. Most of the activity can be found adsorbed on small dark, ball-shaped and very hard particles, composed of clay minerals, iron hydroxides, manganese hydroxides and organic matter. The origin of this radium anomaly and the strong disequilibrium in the uranium series in soils of the Swiss Jura Mountains is probably a continuous chemical weathering of limestone fragments within the soil column. Uranium is released during weathering and migrates as stable uranyl carbonate complexes through the soil column. In contrast, its decay products (230Th and 226Ra) are strongly sorbed to the above mentioned particles. It is not very likely that such a radium anomaly is limited to the Swiss Jura Mountains. It thus would be worth to look for high radium concenrations in Karst soils worldwide.Paper presented at 5th International Symposium on Karst (Malaga, 14-16 October 2014)
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