γ-Spectroscopy measurement of natural radioactivity and assessment of radiation hazard indices in soil samples from oil fields environment of Delta State, Nigeria

The analysis of naturally occurring radionuclides (R-226 a, Th-232 and K-40) has been carried out in soil samples collected from oil and gas field environment of Delta state, using gamma spectroscopy operated on a Canberra vertical high purity 2 '' x 2 '' Nal(TI) detector. The activity concentration of the samples ranges from 19.2 +/- 5.6 Bqkg(-1) to 94.2 +/- 7.7 Bqkg(-1) with mean value of 41.0 +/- 5.0 Bqkg(-1) for Ra-226, 17.1 +/- 3.0 Bqkg(-1) to 47.5 +/- 5.3 Bqkg(-1) with mean value of 29.7 +/- 4 Bqkg(-1) for Th-232 and 107.0 +/- 10.2 Bqkg(-1) to 712.4 +/- 38.9 Bqkg(-1) with a mean value of 412.5 +/- 20.0 Bqkg(-1) for K-40. These values obtained are well within the world range and values reported elsewhere in other countries, but are little above some countries reported average values and some part of Nigeria. The study also examined some radiation hazard indices, the mean values obtained are, 98.5 +/- 12.3 Bq.kg(-1), 0.8 Bqkg(-1), 54.6 eta Gyh(-1), 0.07 mu Svy(-1), 0.3 and 0.4 for Radium equivalent activity (Ra-eq), Representative level index (l gamma), Absorbed Dose rates (D), Annual Effective Dose Rates (E-ff Dose), External Hazard Index (Hex) and Internal Hazard Index (H-in) respectively. These calculated hazard indices to estimate the potential radiological health risk in soil and the dose rate associated with it are well below their permissible limit. The soil and sediments from the study area provide no excessive exposures for inhabitants and can be use as construction materials without posing any immediate radiological threat to the public. However, oil workers in the fields and host communities are cautioned against excess exposure to avoid future accumulative dose of these radiations from sludge and sediment of this area. (C) 2011 Elsevier Ltd. All rights reserved.