Study of Natural Radioactivity Levels in Environmental Samples (Building Materials) in Dejen District, East Gojjam, Ethiopia
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Date
2023-12
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Addis Ababa University
Abstract
All materials derived from rock and soil contain varying levels of natural radioactive isotopes such as 238U and 232Th and their decay products as well
as 40K. Therefore, whether willingly or unwittingly, humans are constantly exposed to radiation emitted by radionuclides.
The purpose of this study is to determine the levels of naturally occurring radioactivity and their risk indices in raw gypsum, soil samples, and building-related raw materials (sand, limestone, clay, gypsum, pumice, and coal used in cement production) in East Gojjam, Dejen district, Ethiopia.
Raw gypsum samples were collected from the production site of five gypsum factories, while soil samples were collected from agricultural and virgin lands. Raw building materials that are used for cement production were also collected from cement factories. All the samples were prepared and packed for measurement using standard methods [1].
The specific activities of 238U, 232Th, and 40K were computed using a p-type, coaxial, Canberra High Purity Germanium (HPGe) detector. The detector
is used in conjunction with a multichannel analyzer that features an analog-to-digital converter for data acquisition and Genie 2000 multichannel analyzer software with 8192 channels to analyze spectra. In raw gypsum samples it was determined that 238U, 232Th, and 40K are found, with mean specific activities of 1.90 _ 0.33, 1.99 _ 0.39, and 28.16 _ 2.57 Bqkg1, respectively, which are significantly lower than the intercontinental approved values. All the radioactive risk indices calculated were significantly lower than the global recommended values. The results of various radioactive indices show that using gypsum powder obtained from studied samples in the construction of residences is safe.
The calculated mean activity concentrations of 226Ra, 232Th, and 40K in agricultural soils were 33.44 _ 2.01, 66.02 _ 4.54, and 214.16 _ 8.90 Bqkg1, respectively, while in virgin soils they were 38.05 _ 2.48, 61.78 _ 4.76, and 240.32 _ 10.79 Bqkg1, respectively. The findings were discussed and compared to those of other studies. The mean values of absorbed dose rate, annual effective dose rate, radium equivalent activity, external hazard index, internal hazard index, radioactivity level index and excess lifetime cancer risk in agricultural land soils are 67.24 nGyh1, 0.083 mSvy1, 144.57 Bqkg1, 0.39, 0.48, 1.03 and 0.29_103, and in virgin land soils are 67.53 nGyh1, 0.082 mSvy1, 144.90 Bqkg1, 0.39, 0.49, 1.03 and 0.29_103, respectively. These results were compared and contrasted to the internationally recommended value.
The activity concentrations of 226Ra, 232Th, and 40K, as well as their radiation risk indices, were measured in raw material samples (sand, limestone, clay, gypsum, pumice, and coal) used in cement production. 226Ra, 232Th, and 40K activity concentrations in the tested samples ranged 4.90 _ 0.49 to 37.43 _ 2.57, 2.97 _ 0.42 to 72.08 _ 5.53, and 2.58 _ 1.28 to 208.78 _ 9.70 Bqkg1, respectively. For 226Ra, 232Th, and 40K, the clay sample had the highest activity concentration (37.33 _ 2.36, 71.06 _ 5.45, 208.66 _ 9.69 Bqkg1) and the gypsum sample had the lowest activity concentration (5.18 _ 0.55, 4.95 _ 0.61, 54.36 _ 3.40 Bqkg1). With the exception of clay samples for radium and thorium, these values are significantly lower than the corresponding worldwide mean values. The average results were compared to those of comparable studies conducted in other countries, as well as global average values. The received doses and radiological hazard characteristics were calculated and compared to global average values to determine the exposure risk associated with the use of these raw materials. Except for the increased lifetime cancer risk, the mean total estimated radiation hazard indices are below the recommended limits.
This study demonstrated that the evaluated samples for raw gypsum; raw materials used in cement production and soil samples used in building construction are safe for residents and those involved in agricultural activities, and no additional radiological health risks are present in any of the studied samples.
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Study of Natural Radioactivity Levels, Environmental Samples, Dejen District, East Gojjam, Ethiopia