Distribution of radionuclides in soils of drainage basin/cerrado biome and their relationship with the land occupation and use model

Abstract

It is essential to know the level of radiation in the environment to develop and implement control programs to protect humans from exposure to high levels of contamination. As cerrado soils contain heavy metals and radionuclides in their composition due to agricultural activities, the objective of this study was to evaluate the concentrations and distributions of radionuclides such as potassium (⁴⁰K), uranium (²³⁸U), and thorium (²³²Th) in the soils of the cerrado biome of the Bonito River drainage basin, and their relationship with the land occupation and use model. Gamma-ray spectrometric measurements were performed at 38 sampling points in this study. The highest three concentrations of radionuclides were detected at points 14, 16 and 32 for ²³⁸U (209.03, 221.35 and 224.28 Bq kg⁻¹), at points 21, 20 and 32 for ²³²Th (133.53, 148.08 and 154.30 Bq kg⁻¹), and at points 8, 32 and 13 for ⁴⁰K (381.23, 470.75 and 698.93 Bq kg⁻¹). In the analysis of variance at 5% probability level for the factors of rock lithology and particle size of the soils, the concentrations and distributions of the radionuclides were significant. The first component of the principal component analysis (PCA), and the basic cations calcium (Ca²⁺), magnesium (Mg²⁺) and potassium (K⁺) showed high correlation. It indicates the importance of cationic macronutrients in plant nutrition. The results of this study proved to be valuable for explaining and understanding the presence and distribution of ⁴⁰K, ²³⁸U and ²³²Th in drainage basins on cerrado biomes in relation to the different natural and anthropogenic aspects of the landscape. In this sense, it was considered that clay-textured soils have higher chemical retention capacities of radioactive species. This could be useful for evaluating the radionuclide pollution in drainage basins of different regions around the world.