Crude oil samples were collected from six different fields in the central Niger Delta in order to determine their natural radioactivity and trace element contents, with the aim of assessing the radiological health implications and environmental health hazard of the metals, and also to provide natural radioactivity baseline data that could be used for more comprehensive future study in this respect. The activity concentrations of the radionuclides were measured using a well, accurately calibrated and shielded vertical cryostat, Canberra coaxial high-purity germanium (HPGe) detector system, and the derived doses were evaluated. The metal concentrations were determined by the graphite furnace atomic absorption spectroscopic (GFAAS) method. The radionuclides identified with reliable regularity belong to the decay series of naturally occurring radionuclides headed by 238U and 232Th along with the non-decay series radionuclide, 40K. The averaged activity concentrations obtained were 10.52 ± 0.03 Bq kg−1, 0.80 ± 0.37 Bq kg−1 and 0.17 ± 0.09 Bq kg−1 for 40K, 238U and 232Th, respectively. The equivalent doses were very low, ranging from 0.0028 to 0.012 mSv year−1 with a mean value of 0.0070 mSv year−1. The results obtained were low, and hence, the radioactivity content from the crude oils in the Niger delta oil province of Nigeria do not constitute any health hazard to occupationally exposed workers, the public and the end user. The concentrations of the elements (As, Cd, Co, Fe, Mn, Ni, Se and V) determined ranged from 0.73 to 202.90 ppb with an average of 74.35 ppb for the oil samples analysed. The pattern of occurrence of each element agreed with the earlier studies from other parts of the Niger Delta. It was obvious from this study and previous ones that the Niger Delta oils have low metal contents. However, despite the low concentrations, they could still pose an intrinsic health hazard considering their cumulative effects in the environment. Also, various studies on the impact of oil spillage and activities of oil exploration and production on organisms in the immediate environment suggest this.

Natural radioactivity and trace metals in crude oils: implication for health.

Radioactivity measurements have been carried out using gamma-ray spectroscopy to determine the radionuclide concentrations in soil samples in the premises of the Warri Refining and Petrochemical Company located in the Niger Delta region of Nigeria and also in communities around it. The radionuclide contents of the crude oil and petroleum additives were also similarly determined. Results indicate that on the premises used by the company, the ranges of activity concentrations of 40K, 226Ra and 228Th in the soil samples were 261.3–932.3 Bq kg−1,<4.2–23.0 Bq kg−1 and<5.1–10.2 Bq kg−1, respectively. For the 13 villages studied, activity concentrations ranged from <17.2–766.3 Bq kg−1,<4.2–104.7 Bq kg−1 and<5.1–13.7 Bq kg−1, respectively, for 40K, 226Ra and 228Th. The lowest radionuclide concentrations were found in the crude oil relative to the petroleum additives. The highest outdoor effective dose rate obtained in the study was 47.5 µSv y−1 for the villages and 35.2 µSv y−1 within the company premises. These values are less than the world average outdoor value of 70 µSv y−1 given by UNSCEAR. Overall, it can be concluded that the long duration of refining activities does not seem to have affected radionuclide concentrations in the environment. Measurements also showed that the observed radiation dose rates did not vary significantly from the previously determined Warri City outdoor gamma radiation dose rates, for which the probability of occurrence of any health effects of radiation was judged low. The measurements, therefore, are interpreted to represent baseline radiometric data for future reference and research in the area.

https://iopscience.iop.org/article/10.1088/0952-4746/28/3/006/pdf

Soil radionuclide concentrations and radiological assessment in and around a refining and petrochemical company in Warri, Niger Delta, Nigeria.

Coal petrography, mineralogy and geochemistry of lignite samples from the Ogwashi–Asaba Formation, Nigeria

An accurate quantitative determination of halide ions X (X = Cl, Br, I) in aqueous solution by total reflection X-ray fluorescence (TXRF) is not possible using the traditional acidic internal standards. In general, the standard solutions are highly acidic (e.g., Ga(NO3)3 in HNO3) to avoid precipitation of hydroxides of the standard element and to obtain a stable and reliable standard. In acidic solutions, dissolved halide salts can exchange their cation for a proton. The resulting volatile HX compounds can evaporate during the drying procedure of the TXRF sample preparation. In this technical note, we show that an alkaline Cu(NH3)4(NO3)2 standard can be used for the determination of chlorine, bromine and iodine without facing problems of HX evaporation.

Determination of halide ions in solution by Total Reflection X-ray Fluorescence (TXRF) spectrometry.

The radionuclide contents in waste products and physico-chemical characterization of effluent samples from some selected industries in the city of Lagos were carried out. The radioactivity concentration levels due to 40 K, 226 Ra and 228 Th in the solid wastes were determined using gamma-ray spectrometry while physico-chemical determination of parameters were based on standard methods of measurements. The average radioactivity levels obtained was between 104 ± 14 Bq kg -1 and 1276 ± 31 Bq kg -1 for 40 K, 86 ± 18 Bq kg -1 and 122 ± 23 Bq kg -1 for 226 Ra and while for 228 Th it ranged between 14 ± 2 Bq kg -1 and 73 ± 10 Bq kg -1 . No artificial radioactive elements were detected in any of the samples. The average outdoor effective dose rate due to gamma exposure from these waste materials in the city was calculated as 0.12 mSv y -1 . This is far less than 1 mSv y -1 recommended limit for the member of the public by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The pH of the effluent samples was slightly alkaline, while the electrical conductivity ranged between 275 and 455 µS cm -1 and total suspended solids ranged from 104 to 5616 mg l -1 . All these ranges and those of biochemical and chemical oxygen demand values were all higher than the prescribed limits. Presence of heavy metals in the effluent samples was however lower than prescribed with the exception of iron.

/pdf/radionuclide-contents-and-physico-chemical-characterization-3d5yfqlmdg.pdf

Radionuclide contents and physico-chemical characterization of solid waste and effluent samples of some selected industries in the city of Lagos, Nigeria

Radioassay of prominent Nigerian fossil fuels using gamma and TXRF spectroscopy

Water samples from boreholes collected from 29 locations in two local government areas in Port Harcourt, Rivers State, Nigeria have been analysed for their natural radioactivity content using a well-calibrated, shielded and highly efficient NaI(Tl) detector based gamma ray with a view to provide baseline data on the radioactivity level in the area, as well as an estimate of the resulting dose on the inhabitants. The radionuclides observed with reliable regularity belonged to the decay series chain headed by (238)U and (232)Th as well as the non-series (40)K. The mean specific activity concentrations of these, are 3.51 +/- 1.22, 2.04 +/- 0.29 and 23.03 +/- 4.37 Bq l(-1), respectively. The respective corresponding estimated mean annual effective dose are 0.36 +/- 0.12, 0.51 +/- 0.07 and 0.05 +/- 0.01, respectively mSv y(-1). These results are relatively high but are still below the recommended limit of 1 mSv y(-1) due to borehole water only. This study is the first in the area and can usefully be associated with similar surveys in other matrices in the area. Meanwhile, the radionuclides detected in the water samples do not seem to pose any radiological consequence on the sample population.

P. Tchokossa

Papers

Radioassay of prominent Nigerian fossil fuels using gamma and TXRF spectroscopy

Natural radionuclides in borehole water in Port Harcourt, Rivers State, Nigeria