Soil Radon Concentration Research Articles

Residential, soil and water radon surveys in north-western part of Romania

The exposure to radon and radon decay products in homes and at workplaces represents the greatest risk from natural ionizing radiation. The present study brings forward the residential, soil and water radon surveys in 5 counties of Romania. Indoor radon measurements were performed by using CR-39 track detectors exposed for 3 months on ground-floor level of dwellings, according to the NRPB Measurements Protocol. Radon concentrations in soil and water were measured using the LUK3C device. The indoor radon concentrations ranged from 5 to 2592 Bq⋅m−3 with an updated preliminary arithmetic mean of 133 Bq⋅m−3, and a geometric mean of 90 Bq⋅m−3. In about 6% of the investigated grid cells the indoor radon concentrations exceed the threshold of 300 Bq⋅m−3. The soil gas radon concentration varies from 0.8 to 169 kBq⋅m−3, with a geometric mean of 28.4 kBq⋅m−3. For water samples, the results show radon concentrations within the range of 0.3–352 kBq⋅m−3 with a geometric mean of 7.7 Bq⋅L−1. The indoor radon map was plotted on a reference grid developed by JRC with the resolution 10 × 10 km2.

Correlation Between Underground Radon Gas and Dormant Geological Faults

This work studies the concentration of radon in soil around a fault in the East Franklin Mountains in the El Paso area in West Texas. It is found that the in-soil production of radon is correlated to the existence of a fault even if it has not had any recorded activity in recent geological times. This adds to previous observations that link the production of radon to seismic activity, and seems to indicate that in non-active faults the radon production is due mainly to the radioactivity of the top soil and to the transport properties of the medium and not to deeper seismic activity. These results open the possibility of using in-soil radon gas concentrations as an examination tool of dormant faults.

The correlation between indoor and in soil radon concentrations in a desert climate

This study examines the levels and the correlation between indoor and in soil radon concentration in a desert climate. The measurements are carried out, in Jordan desert in AlMafraq district, using the passive integrated technique. An intelligent automated tracks counting system, modified recently by our group, is used to estimate the overlapping tracks and to decrease the counting percentage error. Results show that radon concentration in soil expands from 4.09 to 11.30kBqm−3, with an average of 7.53kBqm−3. Indoor radon concentrations vary from 20.2Bqm−3 in the AlMafraq city to 46.7Bqm−3 in Housha village and with an average of 29.6Bqm−3. All of individual indoor radon concentrations are lower than the limit (100Bqm−3) recommended by WHO except two dwellings in Housha village which found being higher than this limit. A moderate linear correlation (R2=0.66) was observed between indoor and in soil radon concentrations in the investigated region. Our results showed that an in soil radon measurement can be a satisfactory predictor for indoor radon potential.

Variation in the radon concentrations and outdoor gamma radiation levels in relation to different geological formations in the thermal regions of Bursa, Turkey

Spring waters used as spas and their region may contain significant amounts of natural radionuclides. The main sources of exposure are the inhalation of radon and its decay products released from the water and soil and terrestrial gamma-radiation. In order to evaluate the potential risk of thermal regions in Bursa, located in the impact area of the NAF (North Anatolian Fault), radon and thoron concentrations in soil gas, radon concentrations in thermal waters and outdoor gamma radiation levels were measured in thermal regions that have different geological formations. The radon and thoron concentrations in soil–gas were found to vary from 2272 ± 121 to 245196 ± 3455 Bq m−3 and from 999 ± 218 to 178 848 ± 17 742 Bq m−3, respectively. The radon concentrations in thermal waters ranged from 0.99 ± 0.21 to 226.74 ± 2.51 Bq l−1 in the rainy season and from 0.26 ± 0.10 to 178.03 ± 12.86 Bq l−1 in the dry season. The measured outdoor gamma radiation levels varied from 38 to 180 nGy h−1. The gamma dose rates were found to be strong positively correlating with the radon and thoron concentrations in soil–gas. The radon and outdoor gamma radiation levels were observed to be a function of the geological formations of the area.

Thermo-diffusional radon waves in soils

A new theoretical framework for diurnal and seasonal oscillations of the concentration of radon in soil and open air is proposed. The theory is based on the existing temperature waves in soils and thermo-diffusional gas flux in porous media. As soil is a non-isothermal porous medium, usually possessing a large fraction of microscopic pores belonging to Knudsen's free molecular field, a thermo-diffusional gas flow in soil has to arise. The radon mass transfer equation in soil for sinusoidal temperature oscillations at the soil–atmosphere boundary is solved, which reveals that radon concentration behaves as a damped harmonic wave. The amplitude of radon concentration oscillations and phase shift between radon concentration oscillations and soil temperature depend on the radon diffusion coefficient in soil, rate of radon production, soil thermal conductivity, average soil temperature, decay constant, and heat of radon transfer. Primarily numerical calculations are presented and comparisons with experimental data are shown.

Natural and fallout radioactivity levels and radiation hazard evaluation in soil samples

The present study aims to obtain the baseline data on natural and fallout radioactivity and to evaluate radiation hazards caused by ionizing radiation emitted from 226Ra, 232Th, 222Rn, 40K and 137Cs in surface soil samples collected from Mersin province and Akkuyu nuclear power plant region. The activity concentrations of 226Ra, 232Th, 40K and 137Cs were measured using a gamma spectrometer with HPGe detector. The activity concentrations of 226Ra, 232Th, 40K and 137Cs varied from 14.1 ± 0.7 to 65.4 ± 2.9, 12.0 ± 0.8–51.7 ± 2.1, 172.2 ± 15.8–511.1 ± 37.8 and <MDA to 86.2 ± 1.4 Bq kg−1, respectively. The average concentrations of radon in soil and air were estimated as 23.9 kBq m−3 and 76 Bq m−3. The radiological parameters such as absorbed gamma dose rate in outdoor air (DRout), annual effective dose rate from external exposure (EExt), annual effective dose rate from inhalation of radon (EInh) and lifetime cancer risk (LTCR) were calculated to evaluate radiological hazards. The average values of DRout, EExt, EInh and LTCR were found to be 51 nGy h−1, 62 μSv year−1, 715 μSv year−1 and 2.2 × 10−4, respectively.

SOIL GAS RADON MEASUREMENT AROUND FAULT LINES ON THE WESTERN SECTION OF THE NORTH ANATOLIAN FAULT ZONE IN TURKEY.

Soil gas radon activity measurements were made around the western section of the North Anatolian Fault Zone. In the study, the variation of radon concentration at 12 different locations along the fault line was monitored by using LR-115 (solid-state nuclear track detectors) detectors for 12-monthly periods. Twelve radon stations were determined in the study region, and in each station, LR-115 films were installed in the borehole of ∼50 cm. The recorded radon concentration varies from 29 to 7059 Bqm-3 with an average value of 1930 Bqm-3. The influence of meteorological parameters such as temperature, pressure, total rainfall and humidity on soil radon concentrations in the study area was also investigated. The positive and poor correlation was observed between average value of 222Rn concentration and temperature. There is a reverse proportion between radon level with other meteorological factors (humidity, pressure and rainfall). The results show that the measured soil gas radon activity concentration shows seasonal variation in a highly permeable sandy-gravelly soil with definite seasons without obvious long transitional periods. The summer (from June 2013 to September 2013) is characterised by 1.8 times higher average soil gas radon activity concentration (median is 2.372 kBqm-3) than the winter (from December 2012 to March 2013) (median is 1.298 kBqm-3).

Soil gas radon mapping of Muzaffarabad city, Pakistan

Soil-based radon investigations are of value in correlating radon production and its transportation into buildings through the processes of convection and diffusion. Such studies can help in identifying land areas that pose special concerns. We present preliminary results of soil radon gas measurements at 60 different locations in an attempt to map out the geohazard zone of the city of Muzaffarabad. The seismic geohazard microzonation for the area includes five microzones based on different hazard parameters: a very high hazard zone, a high hazard zone, a moderate hazard zone, a low hazard zone, and a safe zone. Measurements were taken with an active radon monitoring system at the depths of 30, 40, 50, and 60 cm below the ground surface. The results obtained were explained by the lithology of the area. Average soil radon gas concentrations were correlated with the depth from the ground surface and indoor radon values for the study area. No significant correlation was found between soil radon gas and meteorological parameters, however soil radon gas increases as the depth from the surface of the ground grows. The results showed a linear relation between soil radon concentrations with depth from ground surface (R2 = 0.9577). The minimum soil radon concentration (68.5 Bq/m3) was found at a depth of 30 cm in the very high hazard zone, the maximum value (53.300 Bq/m3) at a depth of 60 cm in the seismically safe zone. Measured soil gas radon concentrations at depths of 30, 40, 50, and 60 cm were mapped for high, moderate, and low radon concentrations. Elevated soil radon gas concentrations were found in the safe zone, otherwise considered to be suitable for any type of construction.

Activity concentration of terrestrial and anthropogenic radionuclides (226Ra, 222Rn, 232Th, 40K, and 137Cs) in soil samples

Measurement of the activity concentrations of terrestrial and anthropogenic radionuclides in one hundred fifteen soil samples collected from various locations in Samsun city was taken using a gamma-ray spectrometer with a NaI (Tl) detector. The average activity concentrations of terrestrial radionuclides 226Ra, 232Th, and 40K were measured as 38.1 ± 1.4, 39.3 ± 0.8, and 375.3 ± 10.2 Bq kg−1, respectively. The average activity concentration of anthropogenic radionuclide 137Cs measured in some soil samples was found as 12.1 ± 0.7 Bq kg−1. Radon concentrations in soil and in air were estimated using results of the measurement of activity concentrations of 226Ra. The average concentrations of radon in soil and air were found as 32 kBq m−3 and 101 Bq m−3, respectively. The absorbed gamma dose rate in outdoor air due to terrestrial radionuclides in soil samples varied from 28 to 95 nGy h−1 with an average of 57 nGy h−1. The annual effective dose rates caused from external and inhalation exposure were estimated as 70 and 958 μSv y−1, respectively.

Soil radon dynamics in the Amer fault zone: An example of very high seasonal variations

Soil radon levels of the Amer fault zone have been measured for a 4 year-period with the aim of checking seasonal fluctuations obtained in previous studies and to understand radon origin and dynamics. In this manuscript additional results are presented: updated continuous and integrated soil radon measurements, radionuclide content of soil materials and a detailed analysis of an urban profile by means of the electrical resistivity imaging technique and punctual soil radon, thoron and CO2 measurements. Integrated and continuous measurements present a wide range of values, [0.2–151.6] kBq m−3 for radon, [4.5–39.6] kBq m−3 for thoron and [4.0–71.2] g m−2 day−1 for CO2. The highest soil radon levels in the vicinity of the Amer fault (>40 kBq m−3) are found close to the fractured areas and present very important fluctuations repeated every year, with values in summer much higher than in winter, confirming previous studies. The highest radon values, up to 150 kBq m−3, do not have a local origin because the mean value of radium concentration in this soil (19 ± 5 Bq kg−1) could not explain these values. Then soil radon migration through the fractures, influenced by atmospheric parameters, is assumed to account for such a high seasonal fluctuation. As main conclusion, in fractured areas, seasonal variations of soil radon concentration can be very important even in places where average soil radon concentration and radium content are not especially high. In these cases the migration capability of the soil is given not by intrinsic permeability but by the fracture structure. Potential risk estimation based on soil radon concentration and intrinsic permeability must be complemented with geological information in fractured systems.

Estimation of radon concentration in soil and groundwater samples of Northern Rajasthan, India

In the present investigation, analysis of radon concentration in 20 water and soil samples collected from different locations of Bikaner and Jhunjhunu districts of Rajasthan, India has been carried out by using RAD7 an electronic Radon detector. The measured radon concentration in water samples lies in the range from 0.50 to 22 Bq l−1 with the mean value of 4.42 Bq l−1, which lies within the safe limit from 4 to 40 Bq l−1 recommended by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR, 2008). The total annual effective dose estimated due to radon concentration in water ranges from 1.37 to 60.06 μSV y−1 with the mean value of 12.08 μSV y−1, which is lower than the safe limit 0.1 mSv y−1 as set by World Health Organization (WHO, 2004) and European Council (EU, 1998). Radon measurement in soil samples varies from 941 to 10,050 Bq m−3 with the mean value of 4561 Bq m−3, which lies within the range reported by other investigators. It was observed that the soil and water of Bikaner and Jhunjhunu districts are suitable for drinking and construction purpose without posing any health hazard.

Radon Measurements in Soils along the Coast of Accra from Teshie to Nyanyano, Southeastern Ghana

A study has been undertaken along the coast of Accra (Teshie to Nyanyano) in the Greater Accra Metropolitan Area to investigate the emission of soil radon gas in the area using Lenin Resin (LR) 115 cellulose nitrate detectors. Twenty seven sampling points were considered for the investigation. A set of detectors were buried at a time and were replaced fortnightly for a period of 2 weeks. Three exposures were made at each location. Due to logistics constraints, the detectors were buried in phases over a period of 15 weeks. After the exposure period, the detectors were etched, air dried in the laboratory and the registered alpha tracks were counted using the Spark counter. The track density was calculated and the radon gas concentration was computed. The radon concentrations ranged from 1.40 kBqm -3 to 282.87 kBqm -3 for the period of monitoring. The average soil radon concentration measured during the period of the survey was 24.41 kBqm -3 . Local earthquakes of magnitude ranging from 1.1 to 2.8 on the Richter scale were recorded during the study. Continuous monitoring of the gas could confirm high emanation with the activity of the coastal boundary fault. DOI: http://dx.doi.org/10.5755/j01.erem.71.2.7063

An Investigation of Factors Influencing Indoor Radon Concentrations in Dwellings of Northern Rajasthan, India

Abstract An effort has been made to find possible relationships of indoor radon levels with building construction materials, ventilation condition of dwellings and soil gas radon levels. Indoor radon measurements were made using LR-115 type II cellulose nitrate films and the concentrations were estimated by knowing the track density of films through optical microscope. Soil gas radon levels were measured using RAD7, an electronic radon detector manufactured by Durridge Company, USA. This study sheds light on the seasonal indoor radon activities in Rajasthan dwellings. Maximum values of the indoor radon concentration were observed during the winter and minimum during the summer season. Results show that ventilation rate is inversely proportional to radon level. Highest level of indoor radon concentration was found in the mud type dwellings compared with dwellings made of concrete, cement and marble. A positive correlation (R2 = 0.45) between indoor radon and soil gas radon concentration was observed. A weak positive correlation (R2 = 0.22) was observed between soil gas radon concentration and radium content in soil. Indoor radon concentration was found to be associated with the presence of radon concentration in local soil, building material used for roof, floor and walls, type of ventilation conditions and presence of cracks on the walls/floor. Positive correlation between indoor and soil gas radon concentration suggest the large contribution of local soil towards indoor radon.

The Measurements of Natural Radioactivity, (Radon and Gamma concentrations), around the old fertilizer factory in Basrah/Iraq

Radon concentration, exhalation rate, annual effective dose, radium activity, thorium, uranium potassium and radium equivalent have been measured in the present investigation for soil in the area around the old fertilizer factory in southern of Basrah Governorate. The measurements based on CR39 track detector for passive method, RAD7 for active method and NaI(Tl) for gamma concentration measurements. Average values for radon concentration in soil were 112.04±10.76 Bq/m3 using passive technique and 104.56±6.05 Bq/m3 using RAD7. From the result of the passive technique, area and mass exhalation rates and the annual effective dose were calculated. Gamma ray spectroscopy for the soil samples were performed and found that the average concentrations of 226Ra, 232Th and 40K were 50.89 Bq/kg, 21.74 Bq/kg and 640.4 Bq/kg respectively. Gamma ray hazard indices were calculated and found they are within the world average.

Radon Concentration in Soil and Radon Exhalation Rate at Al-Dora Refinery and Surrounding Area in Baghdad

Radongas concentrations in soil samples were determined from depths (surface, 15, and 30) cm for nine locations in Al-Dora refinery and surrounding area using “sealed can technique” and CR-39 solid state nuclear track detectors. The radon concentration in surface samples ranged from 810.08 to 1380.08 Bq/m3 with an average 1137.71 Bq/m3. The radon concentration in soil at the depth 15 cm was ranged from 490.5 to 1197.52 Bq/m3 with an average 732.78 Bq/m3 and at the depth 30 cm was ranged from 362.07 to 889.53 Bq/m3 with an average 529.41 Bq/m3. The surface exhalation rate in surface soil samples ranged was 0.44, to 0.99 Bq·m-2·h-1 with average 0.61 Bq·m-2·h-1. The surface exhalation rate in soil samples at the depth 15 cm was ranged from 0.22 to 0.64 Bq·m-2·h-1 with average 0.39 Bq·m-2·h-1. The surface exhalation rate in soil samples at the depth 15 cm was ranged from 0.22 to 0.64 Bq·m-2·h-1 with average 0.39 Bq·m-2·h-1. The surface exhalation rate and the mass exhalation rate in soil samples at the depth 30 cm ranged from 0.19, to 0.48 Bq·m-2·h-1 with average 0.28 Bq·m-2·h-1. The mass exhalation rate in surface soil samples ranged from 0.09 to 0.21 Bq·kg-1·h-1 with average 0.12 Bq·kg-1·h-1. The mass exhalation rate in soil samples from depth 15 cm was ranged from 0.046 to 0.14 Bq·kg-1·h-1 with average 0.08 Bq·kg-1·h-1. The mass exhalation rate in soil samples at the depth 30 cm was ranged from 0.042 to 0.1 Bq·kg-1·h-1 with average 0.06 Bq·kg-1·h-1.

Tracing NAPLs contamination in the vadose zone using soil radon

Frequent spills of Non-Aqueous Phase Liquids (NAPLs), such as petroleum products or chlorinated solvents, occur all around the world contaminating the soil vadose zone or the aquifer. In order to trace the presence of these substances, radon concentration in soil gas can be employed because of its high solubility in NAPLs. Radon available in the soil pores accumulates in the NAPLs producing a local decrease of its concentration in the vicinity of contaminated areas. Thus radon minima in the vadose zone can be used to localize NAPL plumes indirectly.The suitability of this method is here checked by laboratory simulation of a gasoline spill within a known volume of soil. Radon activity concentration strongly drops down right after the injection of gasoline and progressively increases in the following days. This trend is compared with data from a simultaneous experiment carried out on a volume of the same soil, not contaminated by NAPL.Finally, an example of field measurements within a site affected by NAPL contamination is documented. Mapping of soil radon concentration at 80 cm depth shows an area where radon deficit is evident. This region is aligned along the directions of the groundwater flow induced by pumping for safety operation of the plant. Radon negative anomalies are not due to low gas permeability and are not correlated with soil CO2. The comparison of soil gas data with those from nearby background areas confirm the soundness of premises.

Seasonal and location dependence of indoor and soil radon concentrations in two villages, Najran region, Saudi Arabia

Seasonal (winter-summer) indoor and soil radon comparison is made in two villages in Najran region, south west of Saudi Arabia, using CR-39 Dosimeter. Summer indoor radon concentrations were measured in the villages of Fara Al-Jabal and Hadadah. The respective winter-summer average values of 42 ± 4 Bq m−3 and 74 ± 5 Bq m−3 are measured in Fara Al-Jable village and the average values of 47 ± 4 Bq m−3 and 76 ± 5 Bq m−3 are measured in Hadadah village. The respective winter-summer soil values are 1.40 ± 0.21 kBq m−3 and 0.99 ± 0.04 kBq m−3 in Fara Al-Jabal village while those measured in Hadadah village are 2.90 ± 0.17 kBq m−3 and 1.40 ± 0.66 kBq m−3. Indoor radon levels are found to be seasonal dependent while that of soil are found seasonal and location dependent. Meteorological and geological factors are expected to have caused the measured significant differences in radon levels in dwellings and soil in the two villages.

Variations of soil radon concentrations along Chite fault in Aizawl district, Mizoram, India.

The present study concerns measurements of radon emissions from soil carried out during March to July 2013 at Chite fault in Aizawl district, Mizoram, India. In this study, continuous radon monitoring in soil was done by using LR-115 type II nuclear track detector (Kodak-Pathe, France make), and the exposed films were replaced weekly. A negative correlation coefficient (-0.47) between radon concentration and barometric pressure was found during the investigation period. The average radon concentration was observed to be 1785.71 Bq m(-3) with a standard deviation of 633.07 Bq m(-3). The maximum and minimum values of radon concentration during this period were found to be 3693.88 and 904.76 Bq m(-3), respectively. An anomalous increase in radon concentration was observed on 112th day (i.e. on 14 June 2013) during the investigation period just 1 d prior to the event of M 3.5, which occurred within 120-km distance from the monitoring site.

A new approach for radon monitoring in soil as an earthquake precursor using optical fiber

Temporal variations of radon concentration in soil before the earthquake are known as an earthquake precursor. For using of radon as an earthquake precursor, it is necessary to constantly monitor radon concentration variations in a relatively wide range in the vicinity of a fault which is virtually impossible for radon detectors that already exist. This paper proposes a new method for continuous measurement of radon concentration variations in a wide range, using optical fiber as radon detector. For this purpose, an experimental system consisting of radon source, optical-fiber holding chamber, radon gas detector, optical laser source, and optical power meter have been arranged to with the aim to create different concentrations of radon gas in the vicinity of the optical fiber; the attenuation which creates on optical fiber is subsequently measured. As a result, the average of the attenuation is 0.004 μw per each meter per Bq/l since the fault’s length is more than ten kilometers; sensitivity of the measurement can be improved many times over.

Temporal variation of soil radon and thoron concentrations in Mizoram (India), associated with earthquakes

Continuous soil-gas radon and thoron measurements were carried out at 15 days interval along Mat fault in Mizoram (India), which lies in the seismic zone V of the seismic zonation map of India. The study was carried out from March 2012 to February 2013 using LR-115 Type II detectors, manufactured by Kodak Pathe, France. The effect of meteorological parameters on radon and thoron data was taken into consideration. The annual average value of radon and thoron concentration was found to be 621.21 and 590.18 Bq/m3 with a standard deviation of 377.60 and 301.34 Bq/m3, respectively. Inverse correlation coefficient was obtained between radon/thoron concentration and the meteorological parameters except in one case (thoron and relative humidity) which showed a weak positive correlation. Standard deviation method was employed in order to differentiate those anomalies which are solely caused by seismic events and not by meteorological parameters. The data obtained have been correlated with the seismic activities that occurred around the measuring site. Positive correlations were found between radon/thoron data and the earthquakes.