One of the main problems in the ecological researches is natural environmental radioactivity. In this study, the activity concentrations of naturally formed 238U, 232Th, 226Ra and 40K radionuclides were measured for various types of soil samples collected from Guangdong Province. Samples in 49 siteswere selected within the study area. The concentration of radionuclides of 238U is in the range from 17.9 to 209.1 Bq/kg, with the average value being 84.3 Bq/kg; that of 232Th varies from 10.6 to 263.8 Bq/kg, with average value being 103.0 Bq/kg;that of 226Ra varies from 12.0 to 206.0 Bq/kg, with average value being 77.7 Bq/kg; and that of 40K varies from 15.3 to 1557.6 Bq/kg, with average value being 463.3 Bq/kg. The gamma absorbed dose rates in air is in the range of 27.2~265.9 nGy/h, with an arithmetic mean of 126.8 nGy/h, while the annual effective dose rates (AEDR) are in the range of 33.3 to 326.1 μSv/y, with an arithmetic mean of 155.5 μSv/y. The calculated values of radium equivalent activity (Raeq) and external hazard index (Hex) for the soil samples in the study area is 260.7 (33.5~619.0) Bq/kg and 1.2(0.15~2.8), respectively. Sample sitesare assigned to regional bedrock, geomorphic landscape and soil type, respectively, resulting in three categorical variables. Random forest regression and correlation analysis show that the bedrock influences the levels of natural radioactivity in soils most seriously, followed by the soil type and then by the geomorphic landscape. The activities determined in Guangdong Province are generally higher than the average values of China and the values abroad, but are lower than the safe range of radioactive level.
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Jian-Zhou YANG, Jing-Jing GONG, Shi-Xin TANG, Shu-Qi HU. The determination of radioactivity concentrations in soil samples and dose assessment in parts of Guangdong Province. Geophysical and Geochemical Exploration, 2020, 44(2): 419-425.
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