Radiological study of soils in oil and gas producing areas in Delta State, Nigeria

Abstract

Measurements of radioactivity concentrations in soils around the oil and gas producing areas in Delta State of Nigeria were carried out using a high-purity germanium detector gamma-ray spectrometer. Soil samples were collected from 20 locations from the study area and analysed. The radionuclides detected are traceable to the primordial series of (238)U and(232)Th as well as (40)K and traces of globally released (137)Cs. The specific activity values ranged between 7 and 60 Bq kg(-1) with a mean of 24±2 Bq kg(-1) for (238)U; while for (232)Th the range was 7-73 Bq kg(-1) with a mean of 29±3 Bq kg(-1). Relatively higher specific activity values were recorded in (40)K with a range of 15-696 Bq kg(-1), while the mean was 256±37 Bq kg(-1). However, a relatively low-specific radioactivity was obtained from(137)Cs with a range of 1-25 Bq kg(-1) and a mean of 7±1 Bq kg(-1). The estimated dose equivalent obtainable per year from these levels of radioactivity is <5 % of the recommended safe level of 1 mSv per annum. Therefore, the area and the use of the soils as building materials may be considered safe.

Assessment of Radioactivity Contents and Associated Risks in Some Soil Used for Agriculture and Building Materials in Cameroon

“…The sealed samples were kept for at least 28 days to allow a stage of secular equilibrium to reach before gamma spectrometry analysis commenced. The counting equipment well described elsewhere [12,16] was a Canberra vertical high-purity coaxial germanium (HPGe) crystal detector, model GC 2018 -7500, serial number b87063 enclosed in a 100 mm thick lead shield and coupled to a Canberra Multichannel Analysing (MCA) computer system. The energy and efficiency calibrations were done using a well calibrated standard soils sources supplied by the International Atomic Energy Agency (IAEA), Vienna, Austria (Reference Material IAEA-375 for radionuclides and trace elements in soil) and some radioactive point sources from the Isotopes Products Laboratories, Burbank, California, USA.…”

“…Here in Nigeria, Tchokossa and his co-workers reported the results of many investigations on the distribution of radioactivity content in various environmental matrices [12][13][14][15][16][17][18][19], while in Cameroon, Makon et al carried out similar research in some edible vegetable cultivated and consumed worldwide [20]. Cameroon is located at the center of both operational and non-operational nuclear reactors and industries (Figure 1), and to the best of my knowledge, there is no published or on-going works on the survey of Cameroonian's soil.…”

Investigation of Gamma-Emitting Natural Radioactive Contents in Three Types of Vernonia Consumed in Cameroon

“…They were oven-dried under a temperature of 87˚C within one day (24 hours) [12], and were withdrawn, then crushed and sieved using a 2 mm sieve mesh. All the samples were placed thereafter in a vertical cylindrical plastic container named Marinelli beaker, previously washed, rinsed with diluted HCl and dried, and sealed for at least four weeks to allow a sufficient time for 238 U and 232 Th to attain a state of secular radioactive equilibrium with their corresponding progenies prior to gamma spectroscopy [12][13][14][15].…”

Assessment of the Radiation Hazard Indices from Terrestrial Radiation in Mining Sites in Benue State, Nigeria

“…Due to the presence of mineral deposits of economically viable grades, mining and extraction of metals are carried out in such mineralised zones of Benue State, Nigeria. Mining activities all over the world have contributed immensely to the disequilibrium of mineral elements and therefore affect the terrestrial ecosystem due to the excavation of large amount of sands [2].…”

“…People of the study area spend almost 6 hours outdoors due to the nature of their routine. The annual effective dose equation was estimated using the following AEDE (outdoor) (mSv/y) = Absorbed dose rate (nGy/h) ×8760 h ×0.7Sv/Gy × 0.25(2)…”