Uranium content in Technosols formed on naturally loaded proluvial sediments

The content of uranium 238 (238U) in naturally evolved soils with a meta-morphic and poorly developed profile, later technogenically contaminated by the activity of the former "Kremikovtsi" metallurgical plant, located at the foot of the Buhov uranium ore field, was investigated. A total of six soil profiles were analyzed, incl. five from the industrial site of the combine and one control. Data on uranium content were obtained by two methods - Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), simultaneously with results for over 50 chemical elements, as well as measured by its daughter product - thorium 234 ( 234Th), determined by gamma spectrometric analysis via multichannel analyzer with high purity germanium detector (HPGe). The results demonstrate that the uranium content of the investigated profiles in single cases exceeds the background norms of 11-173 Bq/kg and is within the range of 50±5 - 180±40 Bq/kg. The maximum values of the studied element are obtained from the coarsest profiles, with the maximum content of coarse sand, which suggests a primary state of uranium in the form of ore minerals or isomorphically included in primary insoluble accessory minerals in the soil of the studied profiles. From the research, the characteristic relationship of the heavy metal with the soil organic matter was not established. Still, an accumulation was observed in the cambic horizons of the metamorphic profiles. A factor for the upward migration and accumulation of uranium is the change of the water-air soil regime and establishment of periodic reducing conditions; as a general conclusion, the natural radionuclide undergoes migration from the surface horizons of the studied Technosols.