Artificial radionuclide levels in land cover of radiological warfare agent test site ‘4’

Assessing the environmental legacy of historical test sites for nuclear weapons and radiological warfare agents (RWAs) is critical for understanding long-term isotopic evolution and evaluating land safety. This study evaluates artificial radionuclide levels ( 241 Am, 137 Cs, 90 Sr and 239+240 Pu) in the land cover of Site ‘4’, a historic RWA testing ground in the Republic of Kazakhstan. Within the 37 km 2 area analysed via pedestrian and discrete gamma spectrometric surveys, 14 radioactively contaminated locations with gross gamma count rates exceeding the experimentally established baseline of 180 cps were identified, totalling ∼0.37 km 2 . Soil analysis revealed 90 Sr activity concentrations exceeding those of other artificial radionuclides by several orders of magnitude, with the highest values at all sampling points recorded in the upper soil layer (0–10 cm). From the vertical 90 Sr distribution within the soil profile, two distribution patterns were identified: (1) high migration into the 10–20-cm layer and below, and (2) high activity concentrations in the 0–10-cm layer, followed by a sharp decrease in the 10–20-cm layer. This differing distribution pattern is attributed to the use of liquid vs. powdered RWA formulations. The maximum total dose rate of the investigated artificial radionuclides to herbaceous vegetation reached 220 μGy/day, driven primarily by 90 Sr exposure. This study fills a critical research gap in the radioecological monitoring of this area and provides precise geographical and radioecological data necessary for the rehabilitation of these lands.