Assessment of radiological parameters of river water and sediment in some oil producing communities of delta state of Nigeria

Gamma ray spectra of natural radioactivity from U-238, Th-232, and K-40 in sediments and water samples from rivers in eleven oil-producing and two non-oil producing communities in Delta state of Nigeria have been evaluated using gamma-ray spectrometer with the hyperpure germanium detector. Measured activity concentrations in water samples ranged from 1.17 Bq L-1 to 14.65 Bq L-1 for 40K; 0.26 Bq L-1 to 3.11 Bq L-1 for Th-232 and 1.05 Bq L-1 to 5.58 Bq L-1 for 238U. The specific activity due to 232Th is found to be relatively low compared to that of U-238 in all the water sample investigated. In the sediment samples, activities of K-40 ranged from 32.47 Bq kg(-1) to 525.1 Bq kg(-1), 232Th ranged from 6.31 Bq kg(-1) to 19.33 Bq kg(-1) and values of U-238 ranged from 4.45 Bq kg(-1) to 18.69 Bq kg(-1). The radiological hazard indices reported in this work include absorbed dose (D), radium equivalent dose (Req), external and internal hazard indices (Hex, Hin), annual effective dose equivalent (AEDE), lifetime average annual dose associated with water resources (LAAD), and excess lifetime cancer risk (ELCR). The values of the radiological hazard indices obtained were observed to be lower than limits internationally reported for both water and sediment, but observed concentration values at the oil-producing study areas are in most cases higher than values from the non-oil producing sites.