Soil radioactivity in Serbia - A critical review

This review paper systematizes and critically analyzes existing studies on soil radioactivity in Serbia, encompassing urban, rural, and agricultural areas, as well as environments under pronounced anthropogenic influence. Available data on activity concentrations of natural radionuclides (²³⁸U, ²³⁵U, ²²⁶Ra, ²³²Th, and ⁴⁰K) and the artificial radionuclide ¹³⁷Cs, obtained using gamma spectrometry, are analyzed. Special emphasis is placed on the interpretation of results from the national soil radioactivity monitoring conducted in 2014 and 2015 at 24 locations across Serbia, as well as the continuous monitoring carried out in 2024 at sites contaminated with depleted uranium during the NATO operation in 1999. The measured values range from 5 to 181 Bq/kg for ²³⁸U, 0.4-8.2 Bq/kg for ²³⁵U, 3.3-295 Bq/kg for ²²⁶Ra, 0.9-128 Bq/kg for ²³²Th, 2-1440 Bq/kg for ⁴⁰K, and 0.03-930 Bq/kg for ¹³⁷Cs. The literature analysis indicates that activity concentrations of natural radionuclides generally fall within the range of natural background radioactivity determined by geological conditions and are consistent with global average values, while ¹³⁷Cs activities are locally elevated, particularly in mountainous and forested areas. Significant methodological and conceptual shortcomings of existing studies are identified, primarily related to the limited number of samples, insufficient spatial and temporal coverage, lack of long-term monitoring at the same locations, non-uniform and non-standardized sampling and measurement procedures, and insufficient transparency regarding sampling depth and sample numbers. A notable lack of studies focusing on industrial and potentially contaminated sites, the impact of fertilizers on agricultural soils, and the limited capability to detect ²³⁵U and assess the presence of depleted uranium is also highlighted. Furthermore, existing studies rarely establish a clear link between soil radioactivity, geological characteristics, and potential health and environmental risks. The paper emphasizes the need to improve a standardized national soil radioactivity monitoring system based on representative sampling and an integrated approach to data analysis.