Abstract
Soil samples were collected at Al-Najaf governorate, Iraq and assessed for radon concentrations using CN-85 detector and uranium concentrations using CN-85 and CR-39 detectors. Also, Some radiation parameters due to radon concentrations were calculated. Radon concentrations were varied from (506.84) Bq/m 3 to (1194.69) Bq/m 3 with an average of (894.21±77.80) Bq/m 3 , while the radium content were varied from (77.19) Bq/kg to (181.95) Bq/kg with an average (136.18±11.84) Bq/kg. The average values of the rate of radon exhalation in term of mass, in term of area and the soil radon concentration contributing to indoor radon activity were (1.01±0.08) Bq/kg.h, (4.56±0.39) Bq/m 2 .h and (18.24±1.58) Bq/m 3 respectively. Also it is found that the average value of effective dose equivalent, annual effective dose and absorbed dose in soft tissues and in lungs were (0.084±0.007) WLM/y, (0.574±0.050)mSv/y, (0.090±0.007) nGy/h and (0.729±0.063) nGy/h respectively. Among other things, uranium concentration using CN-85 and CR-39 detectors were varied from (0.85) ppm to (2.0) with an average (1.5±0.13) ppm and from (1.16) ppm to (2.17) with an average (1.5±0.13) ppm respectively. The correlation between the contributing of radon to indoor with radium content and uranium concentrations with two detectors (CN-85 and CR-39) in clear. Finally, the values of radon concentrations, radium content, radon exhalation rate in term of area, annual effective dose and uranium concentrations in soil samples in the present study were below limits the world average, so can be consider according results the area under study does not pose risk to human health.
Highlights
Uranium is naturally present in soil, rock and water
Determination of radon concentration using CN-85 and the standard deviation (S.D.) calculation in soil samples at some sites of AL-Najaf governorate are carried out using the following equations (Al-Kofahi et al 1992, Khader 1990, Wiegand, 2001): Where: CRn is the radon concentration within the test tube air, above the sample in (Bq·m-3), K is the calibration factor, that was taken as 0.0092 in /(Bq·m-3) (Al-Saadi et al 2015), ρ: Track density of the detectors exposed to the samples under study, T: Exposure time (h), σn (S.D.): standard deviation and X i, X : count and average of count of samples
The radium content was found using this formula (Sonkawade et al 2008): Where: CRa is the radium content of a given sample, M is the mass of the sample (0.040 kg), h is the distance between the detector and the sample, and Te is the effective exposure time which is calculated by Sonkawade et al (2008) as follows: The radon exhalation rate in terms of area was obtained using the following expression (Sonkawade et al 2008, Thabayneh 2016): Where: EA is the radon exhalation rate in terms of mass, V refers to the volume of the cup (m3), T refers to the time of exposure, and A is the area of cross-section of the cup (12.65×10-4 m2)
Summary
Uranium is naturally present in soil, rock and water. The dominant isotope, uranium-238, forms a long chain of decay products that include the key radionuclides such as radium-226 and radon-222. It has been established that the radon is a causative agent of lung cancer when existing in high concentrations (Archer et al 1976) In this context, radium is a solid radioactive element at standard conditions of pressure and temperature (Anderson et al 1983). This work aims to identify alpha particles emitters (222Rn, 226Ra and 238U) in the selected soil samples in Al-Najaf area (Iraq), using CN-85 and CR-39 detectors The radiological parameters, such as the radon exhalation rate in terms of area, the radon exhalation rate in terms of mass, the soil radon concentration contributing to indoor radon activity, effective dose equivalent, annual effective dose and absorbed dose in soft tissues and in lungs will be calculated. To determine the correlation between the radon concentration contributing to indoor radon activity in the soil with radium content and uranium concentrations, two detectors (CN-85 and CR-39) were used
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