Accumulation of artificial radionuclides in vegetation cover in the area of underground nuclear tests locations in the Sary-Uzen site of the Semipalatinsk Test Site

This study aimed to assess the activity contamination levels and transfer of artificial radionuclides (²⁴¹Am, ¹³⁷Cs, ⁹⁰Sr, and ^239+240Pu) from soils to plants at underground nuclear test borehole locations in the Sary-Uzen site of the Semipalatinsk Test Site. Soil and vegetation samples were collected near warfare boreholes with different contamination patterns, conditionally "background" areas, and fallout plume sites. Peak activity concentrations in soils were recorded near borehole No. 102 for ¹³⁷Cs and near borehole No. 215 for ²⁴¹Am, ⁹⁰Sr, and ^239+240Pu. In plants, the highest ¹³⁷Cs and ⁹⁰Sr were observed near borehole No. 102, and that of ²⁴¹Am and ^239+240Pu near borehole No. 215. Transfer factors indicated that plant uptake followed the order: ⁹⁰Sr > ¹³⁷Cs > ^239+240Pu > ²⁴¹Am. Littoral-aquatic plants accumulated more ⁹⁰Sr, whereas terrestrial plants accumulated more ^239+240Pu. The maximum total exposure dose rate to vegetation reached 74 µGy/day. These findings highlight the influence of test type and contamination pattern on radionuclide behavior in ecosystems and provide a basis for radiological risk assessment in former nuclear test areas.