Distribution Dynamics and Descriptive Statistical Analysis of Radionuclides in the Farmland Soils Near Mining Areas in Southwestern Nigeria

Résumé

Abstract Human exposure to ionizing radiation in the environment is mainly due to naturally occurring radionuclides in the soils, building materials and rocks, but the level may vary depending on the anthropogenic activities prevalent in each location. Presently, in Nigeria, there are concerns due to environmental health implications of all sorts of mineral mining and processing spreading across the southwestern states of the country. As a result, a total of 200 composite soil samples were taken in five states in the southwest of Nigeria, close to active mining sites at the rooting (0.2 m) and at deep planting zones (0.5 m) for analysis by gamma-ray spectrometry using NaI(Tl) detector. The activity concentrations of natural radionuclides in the composite soil samples were determined to vary in the order of 40K > 232Th > 226Ra/238U for all locations. In contrast to the other locations, Olode and Igbokoda had average radium equivalent activities (Raeq) to be 1.6 and 1.8 times higher than the reference limit of 370 Bqkg− 1. The estimated excess life cancer risk values were lower than the 0.29 x 10− 3 global average value for soil by UNSCEAR and ICRP. A negative and low skewness value of 0.16 and 1.20 for 40K and 232Th were obtained in Olode and Sagamu. The kurtosis analysis of the activity concentrations was low and negative for soil at Itagunmodi for 40K and 226Ra/238U; Olode for 40K and 232Th; and Igbokoda for 226Ra/238U and232Th where mining activities are common. The variation in the obtained results has been attributed to different agriculture practices and artisanal mining operations in each location.

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