Using Ra-226/Ra-228 disequilibrium to determine the residence half-lives of radium in vegetation compartments

The concentrations of Ra-226 and Ra-228 were studied in different vegetatio n compartments and in available and non-available soil fractions in a Medit erranean scrubland ecosystem. A high percentage of the plant samples showed an apparent discrimination in favour of Ra-226 Ra-228. A linear compartmen tal model was applied to the soil-plant system. It allowed us over to expla in why these discrimination coefficients differed from unity, to obtain the residence half-lives of radium in the different compartments, to estimate the age of the plants, and to simulate the temporal evolution of the radioa ctive concentrations in each compartment. (C) 1999 Elsevier Science Ltd. Al l rights reserved.