Plant uptake of 238U, 235U, 232Th, 226Ra, 210Pb and 40K a from a coal ash and slag disposal site and control soil under field conditions: A preliminary study

The aim of this study was to investigate the uptake of U-238, U-236, Th-232, Ra-226, Pb-210 and K-40 by plants that grow on a coal ash and slag disposal site known for its higher content of naturally occurring radionuclides. Plant species that were sampled are common for the Mediterranean flora and can be divided as follows: grasses & herbs, shrubs and trees. To compare the activity concentrations and the resultant concentration ratios of the disposal site with those in natural conditions, we used control data specific for the research area, obtained for plants growing on untreated natural soil. Radionuclide activity concentrations were determined by high resolution gamma-ray spectrometry. Media parameters (pH, electrical conductivity and organic matter content) were also analysed. We confirmed significantly higher activity concentrations of (238)u, U-235, Ra-226 and Pb-210 in ash and slag compared to control soil. However, a significant increase in the radionuclide activity concentration in the disposal site's vegetation was observed only for Ra-226. On the contrary, a significantly smaller activity concentration of K-40 in ash and slag had no impact on its activity concentration in plant samples. The calculated plant uptake of U-238, U-235, Ra-226 and Pb-210 is significantly smaller in comparison with the uptake at the control site, while it is vice versa for K-40. No significant difference was observed between the disposal site and the control site's plant uptake of Th-232. These results can be the foundation for further radioecological assessment of this disposal site but also, globally, they can contribute to a better understanding of nature and long-term management of such disposal sites. (C) 2017 Elsevier Ltd. All rights reserved.