Dispersion of gamma dose rates and natural radionuclides in the coastal environments of the Unumherin community in Niger Delta

Abstract

The outdoor gamma dose rates and the activity concentrations of potassium-40, uranium-238, and thorium-232 within the study area were carried out using calibrated hand-held gamma detector (RS-125 gamma spectrometer) and NaI(Tl) gamma spectroscopy. The in-situ measurement results of the gamma dose rate indicate that the hotspot is at location 4 with a value of 100 nGyh-1. The results from the NaI(Tl) gamma detector revealed the highest activity concentrations of potassium-40, uranium-238, and thorium-232 to be 288.09, 96.49, and 136.12 Bqkg−1 for sediments and 257.31, 66.93, and 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 according to 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 coastline environment were caused mainly by uranium-238, followed by thorium-232 and then potassium-40 in magnitude. The mean hazard indices calculated for the samples were also observed to be within the global average values recommended by ICRP.