Evaluation of Natural Radioactivity and Radiation Hazards of Soils around Petroleum Products Marketing Company using Gamma Ray Spectrometry

Abstract

This study aimed at evaluating natural radioactivity and radiation hazards of soils around a petroleum product marketing company due to anthropogenic influences using gamma ray spectrometry. Top soils (5 cm deep) were collected from diverse locations inside the premises of the Company using standard analytical technique, while control samples were acquired at approximately 200 m from the study area. Mean activity concentrations of the radionuclides in the test soils were 89.36 Bq/kg for ⁴⁰K, 92.1 Bq/kg for ²³⁸U and 10.95 Bq/kg for ²³²Th, which are more than that of control samples with statistically significant differences. Assessment of the radiological levels of the oil-contaminated soils were done using internal hazard index, external hazard index, annual gonadal dose equivalent, annual effective dose rate, radium equivalent, total absorbed dose rate and representative level index (I_Ÿ). The results showed that mean annual equivalent dose rate of the oil-contaminated soil (0.46 mSv/yr) fell below the permissive annual dose limit (1.0 mSv/yr). Mean internal hazard index (0.55 Bq/kg) and external hazard index (0.30 Bq/kg) values were less than the minimum permissible limit (1.0). Mean annual gonadal dose equivalent value (358.46 µSvy^-1) of the radionuclides was close to the world average of 300 µSvy^-1, while the mean representative gamma index value (0.78) was also less than unity. Estimated mean value (114.65 Bq/kg) of the radium equivalent was also below the world average of 370 Bq/kg, the values are also more than that of the control samples. Though the soils exhibited low gamma radiation, however lengthy term exposure may pose an inherent cancerous ill-health. It is vital to repeat this investigation periodically to avert precarious effects of anthropogenic influences; also indiscriminate discarding of oils should be discouraged.

Keywords:    Gamma ray spectrometry; radionuclide; refined petroleum products; risk assessment; soil.