Non-Linear Dispersion of Gamma Dose-Rates and Natural Radionuclides in the Coastal Environments of Unumherin Community in Niger Delta

Abstract

Abstract The gamma dose rates and the activity concentrations of Potassium-40, Uranium-238, and Thorium-232 in the study area were carried out using calibrated hand-held gamma detector, (RS-125 Gamma-Spectrometer) and NaI (Tl) gamma spectroscopy. The in-situ measurements result of dose rate indicates the hotspot at location 4 with a value of 100 nGyh-1, almost twice higher than the recommended limits. The results from NaI (Tl) gamma detector revealed the highest activity concentrations of Potassium-40, Uranium-238, and Thorium-232 to be 288.09, 96.49, 136.12 Bqkg-1 for sediments and 257.31, 66.93, 96.57 Bqkg for water, respectively. The highest mean activity concentration of Potassium-40 and Uranium-238 was observed in Catfish with values of 151.87 and 38.00 Bqkg-1, whereas the highest value for the activity of Thorium-232 was observed in Tilo Fish with a value of 89.02 Bqkg-1. In comparison, all the observed values are higher than the population-weighted average of 420.00, 32.00, and 45.00 Bqkg-1 for Potassium-40, Uranium-238, and Thorium-232 by UNSCEAR. Geologically, this may be attributed to the marine incursion of regional tectonic subsidence during transgression. Statistically, the correlation results confirmed that the enhanced outdoor dose rates at the coastlines environment were caused mainly by Uranium-238, followed by Thorium-232 and then Potassium-40 in magnitude. The mean hazard indices for the samples were observed to be within the world average values recommended by ICRP. The accumulation of radionuclides by fishes may be via ingestion and adsorption to surfaces, which culminate in speciation and mobility of radionuclides, alongside the feeding habits of fishes and other aquatic animals.