Radiometric analysis and spatial distribution of radionuclides with-in the terrestrial environment of South-Western Nigeria using ERICA tool

Abstract

Samples of soil, grass and organs of herbivore mammal were collected from different sampling locations in five states within the south-western area of Nigeria. The activity concentrations of natural radionuclides such as 40K, 238U and 232Th present in the collected samples were detected with a method of gamma spectrometry using High Purity Germanium detector. These activity measurements and other ecological (site-specific) data were loaded into ERICA Tool (Version 1.2) to examine the radioactivity level of terrestrial non-human biota. Basic statistics like kurtosis, skewness, histogram alongside spatial distribution calculation were performed in order to understand the radionuclide distribution pattern within the samples. The study also examined the radionuclide transfer factor between the soil and the grass samples. The highest activity concentration was recorded for samples collected from Abeokuta and lowest from samples from Iwo. The calculated concentration is in the order of 40K >238U >232Th. The transfer factor calculation revealed the uptake of 232Th by the collected grass samples is larger than that of 238U and 40K. The dose rates acquired with the use of the application of ERICA Tool indicates that higher contribution to the total dose is from internal exposure derived from exposure to 238U and 228Th with a joint contribution of 95.7% for mammals and 96.9% for grasses. The contribution of 40K corresponds to 4.3% for mammals and 3.1% for grass which is quite a low contribution to total dose. The RQexp value for sampled location is below unity while the RQcons exceeds unity for Lagos and Abeokuta. The result of this study would hearten the use of software application to a wide range of ecosystems and could also serve as a reference or pilot for further research regarding ionizing radiation on non-human biota.