Uptake of Endogenous and Exogenous 226Ra by Vegetables from Soils of a Highly Radioactive Region

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Abstract
The Pocos de Caldas Plateau is a weathered alkaline igneous intrusion where several radioactive anomalies (U and Th series) exist. Not only the local soils but also the edible vegetable produced in the region can present 226Ra concentrations up to 10 times higher than those from areas of normal radioactivity. The aim of this work is to evaluate through greenhouse experiments, the uptake of endogenous and exogenous 226Ra by carrots, brown beans and kale grown from four paired local natural and contaminated farm soils. Simultaneously, sequential selective extractions were performed to estimate the partitioning of 226Ra among six geochemical fractions. The results showed that concentration ratios (CRs), related to plant dry weight, for endogenous and exogenous 226Ra in soils, were of the order of 10-2-10-1 and 10-2-100 respectively. The averages of 226Ra exchangeable and residual fractions in soils were: 3.2% and 50.2% for endogenous and 15.4% and 6.0% for exogenous radium. The CRs calculated either in relation to total 226Ra or to the exchangeable fraction in soils showed about the same variability.

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