Assessment of natural radionuclides in soil samples in specific areas on the territory of Lithuania

Abstract

The activity concentrations of soil samples collected from different locations of Lithuania were determined by using HPGe detector based on high-resolution gamma spectrometry system. The following three unique areas in Lithuania have been chosen for the research. Vilnius city is the capital of Lithuania and this is the city with the largest population in the country which is dominated by an anthropogenic environment. Juodkrantė is a recreation area located near the Baltic Sea and Curonian Spit which is included on the UNESCO World Heritage List and has a natural environment and minimal urbanization. Visaginas is special for the nuclear power plant (which is currently being decommissioned). It is the only nuclear power plant in the Baltic States built close to the border with Belarus on the shore of Drūkšiai Lake. The activity concentrations of naturally occurring radionuclides 40K, 226Ra, and 232Th have been measured in different brands of the soil samples taken from Vilnius and Juodkrantė districts and in the technogenic soil samples from the territory of Visaginas Nuclear Power Plant. Among all identified natural radionuclides, the highest level was that of 40K, i.e. the mean value was 414 ± 71 Bq kg−1, while the minimum level was that of 232Th, i.e. the mean value was 4.8 ± 0.8 Bq kg−1. The mean value of 226Ra activity concentration was 13.9 ± 2.0 Bq kg−1. Having measured the activity concentrations of naturally occurring radionuclides 232Th, 226Ra, and 40K, the possible impact of natural radiation on a human has been assessed by calculating the absorbed dose rate (nGy h−1). The average values of calculated absorbed dose rates in the samples were found 27.71 nGy h−1 in Vilnius, 23.25 nGy h−1 in Juodkrantė, and 28.65 nGy h−1 in Visaginas. In the paper, the annual effective dose (mSv) was also calculated: the minimum annual effective dose was found in Vilnius (0.034 mSv) and the maximum in Visaginas (0.035 mSv).