Avwiri G.O., Alao A.A
Abstract: A survey of radioactivity concentration in some commonly consumed Tubers and Cereals within Oil Mining Lease (OML) 58 and 61, Oil and Gas Producing Areas in the Niger Delta Region of Nigeria was carried out. The study Area was divided into six zones A, B, C, D, E, F where Nine (9) Tuber samples and three (3) Cereals were harvested and collected from agricultural farms where they were produced. Food crop/stuff samples were dried at room temperature to a constant weight, powdered and sieved to pass through a 2mm-Mesh. All samples were then sealed in pre-treated 1-L Marinelli beakers for at Least 28 days for secular equilibrium to set-in before Gamma Spectroscopy analysis. The Canberra Passive Gamma Spectrometer with a well calibrated high purity germanium detector (HpGe) system was employed (NaI (T1) Detector, Model Bircom, Preamplifier Model 2001, Amplifier Model 2020, ADC Model 8075, HVPS Model 3105).Mean Specific Activity values obtained for 40K, 226Ra, 228Ra in Cereals are 39.25 8.37 Bqkg-1, 11.39 3.45 Bqkg-1 and 7.87 2.72 Bqkg-1 and for Tubers, the mean Specific Activity values for 40K, 226Ra, 228Ra are 229.35 27.19 Bqkg-1, 15.75 4.53 Bqkg-1, and 10.90 3.72 Bqkg-1 respectively. The Mean Radium equivalent Activity (Raeq) calculated for surveyed Cereals and Tubers are 25.67 Bqkg-1 and 48.62 Bqkg-1. The Mean effective Dose calculated for all surveyed samples ranged from 0.025mSvy-1 to 0.034 mSvy-1 which is far less than the ICRP standard which did not show any significant health impact. The radiation hazard indices (External hazard Index, (Hex), Internal hazard Index (Hin) } calculated in all surveyed samples were less than unity, therefore all food crops/stuffs examined are suitable for consumption. The results obtained are in agreement with other past works in Nigeria and other parts of the world (Mlwilo et al., 2007, Jibiri et al., 2007, Olowo, 1990, Arogunjo et al, 2005, G.Shanthi et al, 2009, Badar, et al., 2003, Baeza, et al., 2001 and others). There are presences of series radionuclide (238U and 232Th) and non-series (40K) in the samples surveyed, but their activity levels were low compared with UNSCEAR Standard and hence were not expected to constitute any health hazard to the inhabitants. However, no 137-caesium was detected. It is recommended that seasonal variations in radionuclide transfer should be investigated and regular monitoring of the areas should be conducted from time to time to check any eventuality as a result of long time consumption of the foodstuffs.
Keywords: Radioactivity, Specific Activity, External Hazard Index Hex Internal hazard Index Hin