Radioactivity in the Mediterranean flora of the Kaštela Bay, Croatia

• Background radioactivity in soil and 14 different Mediterranean plants was studied.
• Concentration ratios of 238U, 226Ra, 232Th, 208Tl, 40K, and 137Cs are reported.
• No statistical difference in CR values between plant groups was found.
• There was a moderate negative correlation between soil activities and CR values.
• No dependency was found between soil parameters and CR, except for 137Cs.

This study refers to background activity concentrations of 238U, 226Ra, 232Th, 208Tl, 40K, and 137Cs in soil and plants of the Kaštela Bay, Croatia and related plant-soil concentration ratios (CR's). Fourteen different Mediterranean plant species growing in natural conditions have been included and were divided into three major plant groups (grasses and herbs, shrub, tree). Radionuclide activity concentrations were determined by means of high resolution gamma-ray spectrometry. Soil parameters (pH, electrical conductivity, and organic matter content) were also analysed. CR ranges were within one order of magnitude for 40K (10−2–10−1), 238U, and 226Ra (10−3–10−2), and two orders of magnitude for 232Th, 208Tl, and 137Cs (10−4–10−2). There was no statistical difference between the plant groups in radionuclide uptake. Overall statistical analyses indicated a moderate negative relationship between soil concentrations and CR values, and no relationship with soil parameters, except a negative one for 137Cs. Comparison with literature showed more agreement with studies that were done in the Mediterranean than with ICRP and IAEA databases. Our data not only describe the natural radioactivity of the Bay, but also create a dataset that could be relevant for further radioecological assessments of the Kaštela Bay.