The Specific Activity of the Naturally Occurring Radionuclides and Artificially Produced ¹³⁷Cs in Soils and Herbaceous Plants of Rostov Oblast

Abstract—This study examined the characteristics of distribution in plants and soils of the naturally occurring (²²⁶Ra, ²³²Th, and ⁴⁰K) and artificially produced (¹³⁷Cs) radionuclides in the conditions of the dry and semi-dry steppes for Rostov Oblast. As the research objects, it involves samples of soils and plants collected in Tsimlyanskii, Volgodonskii, Dubovskii, Proletarskii, and Orlovskii districts of Rostov Oblast in expeditions during 2001–2019. The specific activity (concentration) of the radionuclides in the soil was measured using the gamma-ray spectrometry of radionuclide analysis. The artificially produced ¹³⁷Cs is unevenly distributed in the soil cover and vegetation of Rostov Oblast due to the specific fallout pattern after the Chernobyl disaster. The naturally occurring ²²⁶Ra and ²³²Th are comparable in their specific activity in the soils and herbage within the limits of the standard deviations (20–30%), which averages 21.2 Bq/kg and 24.8 Bq/kg for ²²⁶Ra and ²³²Th in plants and 22 Bq/kg and 27.1 Bq/kg for ²²⁶Ra and ²³²Th in soils. The concentration of ⁴⁰К is 149.4 Bq/kg and 468.5 Bq/kg in plants and soils, respectively; it is governed by distinctive features of solonetzic soils of the dry-steppe zone in Rostov Oblast. Series were created based on specific activity of radionuclides in the plants herbage: ⁴⁰K > ²²⁶Ra ≥ ²³²Th > ¹³⁷Cs.