Radioactivity of soil in Croatia II: <sup>137</sup> Cs, <sup>40</sup> K, and absorbed dose rate
Marko Šoštarić, Branko Petrinec, Mak Avdić, Ljerka Petroci, Milica Kovačić, Željka Zgorelec, Božena Skoko, Tomislav Bituh, Jasminka Senčar, Gina Branica, Zdenko Franić, Iva Franulović, Davor Rašeta, Ivan Bešlić, Dinko Babić
Abstract
Abstract We took samples of uncultivated soil from the surface layer (0–10 cm) at 138 sites from all over Croatia and measured their radionuclide activity concentrations with high-resolution gamma-ray spectrometry. This second part of our report brings the results on 40 K and 137 Cs to complement those on the 232 Th and 238 U decay chains addressed in the first part. Together they give the most complete picture of radioactivity of Croatian soil so far. Activity concentrations of 40 K were the highest in the Pannonian region, and there was an opposite trend for 137 Cs. We found that the concentrations of 137 Cs tended to increase with altitude, annual precipitation, and vegetation density. The concentration ratio of 137 Cs and K in soil, which indicates the potential for 137 Cs entering food chains via uptake by plants, was the lowest in agriculturally important areas in the east of the Pannonian region. In addition, we used the obtained results on activity concentrations to calculate the related absorbed dose rate as a measure of external exposure to ionising radiation from soil. The sum of the absorbed dose rates for naturally occurring radionuclides and 137 Cs showed that external exposure was generally the highest in the Dinaric region and Istrian Peninsula.