γ-Spectroscopy measurement of natural radioactivity and assessment of radiation hazard indices in soil samples from oil fields environment of Delta State, Nigeria
Department of Physics, Federal University of Petroleum Resources, Effurun, Nigeria. Journal of Environmental Radioactivity
(Impact Factor: 2.48).
02/2012; 109:64-70. DOI: 10.1016/j.jenvrad.2011.10.012
The analysis of naturally occurring radionuclides ((226)Ra, (232)Th and (40)K) 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″×2″ NaI(TI) detector. The activity concentration of the samples ranges from 19.2 ± 5.6Bqkg(-1) to 94.2 ± 7.7Bqkg(-1) with mean value of 41.0 ± 5.0Bqkg(-1) for (226)Ra, 17.1 ± 3.0Bqkg(-1) to 47.5 ± 5.3Bqkg(-1) with mean value of 29.7 ± 4Bqkg(-1) for (232)Th and 107.0 ± 10.2Bqkg(-1) to 712.4 ± 38.9Bqkg(-1) with a mean value of 412.5 ± 20.0Bqkg(-1) for (40)K. 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 ± 12.3Bq.kg(-1), 0.8Bqkg(-1), 54.6ηGyh(-1), 0.07μSvy(-1), 0.3 and 0.4 for Radium equivalent activity (Ra(eq)), Representative level index (Iγ), Absorbed Dose rates (D), Annual Effective Dose Rates (E(ff) Dose), External Hazard Index (H(ex)) 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.
Available from: Agbalagba Ezekiel
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ABSTRACT: Oil mineral leases (30, 58 and 61) in Delta and River States are the major oil blocks in the oil and gas rich Niger Delta region of Nigeria that is characterized by environmental degradation from oil and gas activities. This research work presents an analytical approach on natural radioactivity assessment in soil and sediment in 15 oil fields of these OMLs. Concentrations of natural radionuclides (226Ra, 232Th and 40K) were determined using gamma spectroscopy. The mean activity concentration of 226Ra, 232Th and 40K for OML30 is 40.2 ± 5.1, 29.9 ± 4.2 and 361.5 ± 20.0 Bq kg−1, respectively; the corresponding values obtained for OML58 is 20.9 ± 2.8, 19.4 ± 2.5 and 260.0 ± 14.1 Bq kg−1, respectively. While the mean activity concentration of 226Ra, 232Th and 40K for OML61 is 29.3 ± 3.5, 21.6 ± 2.6 and 262.1 ± 14.6 Bq kg−1, respectively. These values obtained show enhanced NORMs, but are well within the world range and values reported in some regions and countries of the world, and are slightly above control values, values obtained in Southwestern region of Nigeria and some countries reported average values. The study also examined some radiation hazard indices, the mean values obtained are 86.6 ± 9.3 Bq kg−1, 0.6 Bq kg−1, 40.8 ηGy h−1, 0.05 μSv y−1, 0.2 and 0.3 for radium equivalent activity (Raeq), representative level index (Iγ), absorbed dose rates (D), annual effective dose rates (E
ff dose), external hazard index (H
ex) and internal hazard index (H
in), respectively. These calculated hazard indices to estimate the potential radiological health risk in soil and sediment are well below their permissible limits. The soil and sediments from the study area provide no excessive exposures for the inhabitants and can be used as construction materials without posing any radiological threat or harm to the public users. However, oil-field workers and host community residents are cautioned against excess exposure to avoid future accumulative dose of these radiations from sludge and sediment of this area.
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ABSTRACT: A survey of radioactivity concentration in soil and water from the Port Harcourt refinery company host community was carried out using the gamma ray spectrometer with NaI(TI) detector to determine the concentration of the primordial radionuclides 226Ra, 232Th and 40K. 20 samples (10 each of soil and water) were collected at random from various parts of the community. The mean specific activity obtained for 40K was 76.64 22.93 Bq kg-1 (soil), with a range of 41.54 14.80 - 175.54 39.53 Bqkg–1 and 58.88 ± 21.66 Bq l-1 (water) with a range of 36.09 14.06 - 121.18 28.75 Bq l-1. For 226Ra (soil), the mean specific activity was 7.43 3.47 Bq kg-1with a range of 6.62 2.24 – 10.10 4.16Bq Kg–1 and 4.16 ± 1.97 Bq l-1 (water) with a range of 2.61 1.23- 5.46 1.66 Bq l-1 and the mean specific activity for 232Th (soil) was 4.71 2.46 Bq kg-1 with a range of 3.25 2.10 - 6.26 4.01 Bq kg–1 and 3.30 ± 1.90 Bq l-1 (water ) with a range of 2.46 2.08 - 4.16 2.07Bq l-1. The radionuclide concentrations in the soil are all lower than the ICRP standards, while those for the water samples are significantly higher (six times for 40K; eight times for 226Ra and 15 times for 232Th). The percentage contribution of each radionuclide to absorbed dose rate in soil and water were also determined. The absorbed dose rates calculated for both samples vary between 24.60 – 79.74 nGy/hr in soil and 18.52 – 54.98 nGy/hr in water. The results of this work indicate that effluents from the refinery have had some impact on the radionuclide concentration of the water and soil of its host community.
Key words: Radionuclide concentration, specific activity, absorbed dose rate, refinery effluent, Gamma spectrometry,
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ABSTRACT: Pengerang area consists of a mix of private plantation, individual residential lots and state land, which is leased for agriculture related activities. The analysis was conducted to determine the specific activity of the initial value and the radiation hazard indices in the surrounding area in Pengerang. This area will be developed into a major downstream for oil and gas. The aims of this preliminary study were 1) to determine the specific activities of 238U, 232Th, 226Ra and 40K of soil samples at six selected areas by Gamma-ray spectrometry and 2) to calculate the radiation hazard indices. The specific activities (Bq/kg) of the samples ranged from 7.08±5.01 to 36.29±25.72 Bq/kg, 5.62±3.98 to 34.53±24.07 Bq/kg, 4.75±3.42 to 24.76±17.66 Bq/kg and 10.58±7.51 to 101.25±72.00 Bq/kg for 238U, 232Th, 226Ra and 40K, respectively. These values were well within the range that reported by UNSCEAR. The study also examined the radiation hazard indices, the mean values obtained were 48.49±28.06 Bq/kg for Radium Equivalent Activity (Raeq), 0.34 Bq/kg for Representative Level Index (Iγ), 21.83 nGy/h for Absorbed dose rates (D), 0.27 mSv/y for Annual Effective Dose Rates (Deff), 0.13 and 0.18 for External Hazards Index (Hex) and Internal Hazard Index (Hin), respectively. These calculated hazard indices were used to estimate the potential radiological health risk in soil and the dose rates associated with it were well below their permissible limit. The overall findings show that no radiological threat to the health of the population in the study area.
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