Measurement of transfer factors from soil-to-plant/food crop of Naturally Occurring Radionuclide Materials (NORMs) in Nigeria: a review

Abstract

One of the most crucial factors in the environmental safety assessment for the local and global communities, situated either in normal background areas or around nuclear facilities, is the uptake of radionuclides from soil by plants, which is typically stated as soil-to-plant Transfer Factor (TF) or Transfer Coefficient (TC). Such a metric, which can be defined as the ratio of radioactivity unit per dry crop mass to that of unit per dry soil mass, is necessary for environmental transfer models, which help to estimate the radionuclide concentrations in agricultural crops and calculate the dose exposure to people. In this article, a number of research studies conducted by scholars in Nigeria, published in both national and international journals, were compiled and reviewed for the purpose of providing an integrated and synthesized overview of the current state of knowledge on NORMs’ transfer factors in Nigeria. The activity concentrations of ⁴⁰K, ²²⁶Ra, ²²⁸Ra, ²³²Th and ²³⁸U were measured by different research groups using gamma ray spectrometry coupled with either NaI(Tl) or HPGe detector. The activity concentrations of natural radioactivity in soils samples were generally higher than the values recorded in plant and food crop samples in almost all the research studies considered in the review. About 79% of the values of soil-to-plant transfer factor of ⁴⁰K in all the studies under review were greater than the recommended value, while the values of transfer factors reported for ²³²Th and ²³⁸U were all greater than the recommended values.