Abstract
Radon exhalation rate from soil is one of the most important factors for evaluation of the environmental radon level. Solid State Nuclear Track Detectors (CR-39) has been widely used for the study of different aspects of radon emission from soil and others. In this paper, we are presenting the results of radon concentration, its exhalation rate and radium content in soil samples collected from different locations of northern part of Aden governorate, south of Yemen. The outdoor radon levels concentrations were found to vary from 264.59Bq m-3 to 539.72Bq m-3 with a mean value of 369.29Bq m-3. The radon exhalation rate in terms of area and in terms of mass were found to vary from 460.08 mBq.m-2.h-1to 938.47mBq.m-2.h-1with a mean value of 642.12mBq.m-2.h-1 and from 25.99mBq.m-2.h-1 to 53.02mBqkg-1.h-1 with a mean value of 36.28 mBqkg-1.h-1. The results of effective radium concentrations in these sites were found to vary from 3.44 Bqkg-1 to 7.01 Bqkg-1 with a mean value of 4.80Bqkg-1. The working level varied from 4.54mWL to 9.26mWL with a mean value of 6.34mWL. The radon annual effective dose was varied from 0.049mSvy-1 to 0.100mSvy-1 with a mean value of (0.068±0.18) mSvy-1 for outdoor and from 0.20mSvy-1 to 0.40mSvy-1 with a mean value of 0.27mSvy-1 for indoor. The results indicate that the soil is quite safe for occupancies and to be used as building materials.
Highlights
Terrestrial radiation is due to various radioactive nuclides that are present in soil, water, air and their abundance changes depending on the geological and geographical features of region
The results of exhalation rates and effective radium content in soil sample are in agreement with the results of A
The radon annual effective dose was varied from 0.049mSvy-1 to 0.100mSvy-1 with a mean value of 0.068mSvy-1 for outdoor and from 0.20 mSvy-1 to 0.40mSvy-1 with a mean value of 0.27mSvy-1 for indoor
Summary
Terrestrial radiation is due to various radioactive nuclides that are present in soil, water, air and their abundance changes depending on the geological and geographical features of region. The external exposure is caused by gamma rays emitted mainly by radionuclides of uranium 238U and thorium 232Th decay series as well as potassium 40K. The internal exposure is caused by radon (222Rn and 220Rn) and its short-lived decay products. Radon is a natural inert radioactive tasteless and odorless gas, whose density is 7.5 times higher than that of air. Radon gas and its radioactive isotopes have special attention among the other naturally radioactive materials, because it has the largest amount of total annual effective dose to humane. There are two important natural occurring isotopes of radon; 222Rn, a direct product of 226Ra in the 238U series and 220Rn a direct product of 224Ra in the 232Th series. Because radon has relatively long half-life enabling it to migrate quit significant distance before decaying and can be found in everywhere [2]
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