Study of radon exhalation from the soil

The influence of meteorological parameters on radon exhalation rate was analyzed. The analyses show a significant influence of precipitation on radon exhalation rate. The highest exhalation rate was found during dry periods and the lowest during the periods of strong precipitation. We also tested two different types of detectors for the measurement of radon exhalation rate—the ionization chamber (AlphaGUARD) and the scintillation chamber of Lucas type. The exhalation rates measured by these detectors were in a good agreement. Likewise, there was an agreement in radon exhalation rates determined from short term and long term increases in radon activity concentration.     

Seasonal and diurnal variations of radon/thoron exhalation rate in Kanto-loam area in Japan

Radon and thoron concentration in the outdoor environment are affected by the magnitude of the exhalation rate that can vary diurnally and seasonally. This paper presents measurement results of radon and thoron exhalation rates and gamma-ray dose rate in different season at same location points in Gunma Prefecture Japan. Exhalation rates were measured by the MSZ instrument which is based on the accumulation method. Three measurement points Katashina Village, Midori City and Takasaki City were selected for measurement. Soil water saturation and soil temperature were measured to investigate their relationship with exhalation rate. The diurnal variation of exhalation rate may be correlated with soil temperature but no clear relationship was found between them. The gamma-ray dose rate do not vary significantly at the same places even in different season. The average radon exhalation rates were 11 ± 2, 2 ± 1, 5 ± 3 and 11 ± 4 mBq m⁻² s⁻¹ for spring, summer, autumn and winter, respectively. Those for thoron were 1,100 ± 100, 120 ± 30, 250 ± 80 and 860 ± 140 mBq m⁻² s⁻¹. Thus there was a variation of radon and thoron exhalation rate with different seasons. The radon and thoron exhalation rates in the summer and autumn surveys are higher than those in the spring and winter surveys which were affected by rainfall. It indicates that water saturation is an influential factor for radon and thoron exhalation rates.     

Radon emanation coefficient and its exhalation rate of wasted petroleum samples associated with petroleum industry in Egypt

Wasted petroleum, scale and sludge, samples associated with petroleum industries have elevated level of radionuclides concentrations which increase the radiation dose received to the workers. Radon concentration, emanation coefficient and exhalation rate give good information about the radioactivity levels. Twelve samples of scale, sludge and sand, collected from different oil fields in the Red Sea Refineries company for petroleum services in the eastern desert of Egypt, were selected for this study. Radon concentration released from selected samples was measured using AlphaGUARD radon monitor. Radon emanation coefficient and its exhalation rate were calculated based on the measured value of radon concentration. Correlation among radon exhalation rate with radium content and “emanated radon concentration” (radium concentration × emanation coefficient) as well were found to be of 0.94 and 0.99, respectively. Therefore, radon exhalation rate could be useful index for both radium concentration and emanated radon. Radon emanation coefficient was increased more than twice due to water content within material of less than of 10 %.     

Measurement of the radon exhalation rate from the medium surface by tracing the radon concentration

The paper will present a method based on the accumulation chamber technique for measuring of radon exhalation from the medium surface. A radon monitor traces the change of radon concentration in the accumulation chamber, and then the radon exhalation can be obtained accurately through linear fit. Based on our recent experiments, the radon exhalation rate from the medium surface obtained from this method is in good agreement with the actual exhalation rate of our simulation facility. This method is superior to the competition method which obtains the radon exhalation through the exponential fit by an external PC-system. The calculation for the exponential fit is very easy by computer and related software. However, for portable instruments, the single chip microcomputer can’t calculate the exponential fit rapidly. Thus, this method is usable for developing the new portable instrument to classify building materials, etc.     

Study of variation of soil radon exhalation rate with meteorological parameters in Bakreswar–Tantloi geothermal region of West Bengal and Jharkhand,India

Radon gas is the predominant ionizing radiation on earth. Its occurrence is controlled by the presence of uranium in all types of rocks in the earthcrust, apart from local geological features and atmospheric factors which influence its release into the atmosphere. The present work deals with 24 h observation of the dependence of radon exhalation rate from soil on local meteorological parameters at four locations in Bakreswar–Tantloi geothermal region, located in the highly faulted Chhotanagpur Plateau of eastern India. This study is the primary step towards the determination of soil radon exhalation dynamics in this geothermal area.

     

A simple technique for studying the dependence of radon and thoron exhalation rate from building materials on absolute humidity

Indoor radon and thoron concentrations were dominated with their exhalation rate from building materials. Thus, the evaluation of exhalation rate with highly precise is important. This paper presented a new technique to measure the dependence radon/thoron exhalation rate, from building materials used in Japan, on absolute humidity. The measurement technique consisted of a solid state alpha detector equipped a ventilation-type chamber and humidity control system in a flow through method. The exhalation rate of dried samples (Indian red granite and Japanese gray granite) was measured at various absolute humidity levels in the range of 1–20 g cm⁻³. It was found that exhalation rate increased exponential with increasing of absolute humidity for both samples. Furthermore, the dependence of radon emanation coefficient on building material’s temperature was also studied using an accumulation chamber equipped with scintillation cell alpha detector. The emanation coefficient of dry sample increased proportionally with increasing the material’s temperature with a correlation factor of 0.88.     

Ground-truthing predicted indoor radon concentrations by using soil-gas radon measurements

Predicting indoor radon potential has gained in importance even asthe national radon programs began to wane. A cooperative study to produceradon potential maps was conducted by the Environmental Protection Agency(EPA), U.S. Geological Survey (USGS), Department of Energy (DOE), and LawrenceBerkeley Laboratory (LBL) with the latter taking the lead role. They developeda county-wide predictive model based dominantly on the National Uranium ResourceEvaluation (NURE) aerorad data and secondly on geology, both small-scale databases. However, that model breaks down in counties of complex geology anddoes not provide a means to evaluate the potential of an individual home orbuilding site. In this current study, soil-gas radon measurements on a largescale are shown to provide information for estimating radon potential at individualsites sort out the complex geology so that the small-scale prediction indexcan be validated. An example from Frederick County, Maryland indicates a positivecorrelation between indoor measurements and soil-gas data. The method doesnot rely on a single measurement, but a series that incorporate seasonal andmeteorological considerations.     

The measuring of radon volumetric activity and exhalation rate in ground-level air

The physical and chemical characteristics of radon gas make it a good tracer for use in the application of atmospheric transport models. Radon exhalation rate from soil is one of the most important factors for evaluation of the environmental radon level. For this purpose to find out the volumetric activity of radon in ground-level air the measuring has been made using radon monitor SARAD RTM 2200. Radon volumetric activity and radon exhalation rate in ground-level air and at different depths of soil depending on soil temperature and atmospheric parameters in different seasons of the year was calculated and evaluated in two areas of Vilnius city. It has been established that the volumetric activity of radon and radon exhalation intensity is vertically distributed and the corresponding increase in deeper soil layers, and depends on the specific activity of radium, soil temperature and moisture content, temperature difference between soil and atmospheric temperatures.     

Comparison of thoron (220Rn) content and gamma radiation level in high background radiation area of Kollam district in Kerala,India

In order to map the thoron prone areas of the coastal region of Kollam district, a well known HBRA of south India, comparative study of radon and thoron exhalation rate was conducted. The in situ measurement of radon and thoron exhalation has been taken. These studies were correlated with the gamma radiation level. The average value of thoron exhalation is found to 5.55 ± 1.35 Bq m⁻² s⁻¹ along the coastal areas and the radon exhalation rate is found to 107.6 ± 32 Bq m⁻² h⁻¹. The value of thoron exhalation was found 12 times greater than the global values in Neendakara and Chavara region and about 6 times greater in the Alappad region.

     

Modeling of the radon exhalation from water to air by a hybrid electrical circuit

A new model based on electric circuit theory has been introduced for modeling the radon exhalation from water to air in a sample bottle. Comparing the differential equations for radon exhalation from water to air and a hybrid electrical circuit shown that the volume of water or air, radon concentration, radon flux and solubility coefficient (dependent on temperature of water) are equivalent with capacitance, voltage across of capacitor, current and voltage gain, respectively. Then by using a hybrid electrical model total radon transfer velocity from water to air and time variation of water radon concentration in our experimental setup has been obtained. Also the variations of air radon concentration with temperature, volume of water and volume of air is obtained. The results show a good agreement with those in literatures.     

成都市三环地区地基土壤氡含量测量

对成都市三环地区地基土壤中氡含量进行了检测,掌握了区域性氡含量的分布状况,探讨了整个成都市待建地坪基础中的放射性水平,并佐以对成都市地质构造的浅析,为今后城市化进程中的新建、扩建建筑的地下防氡设计提供依据,以最终提升市民的生活环境质量。     

Natural radionuclides content and radon exhalation rate from Brazilian phosphogypsum piles

Phosphogypsum is a waste of the wet-acid process for producing phosphoric acid from phosphate rock. For every ton of phosphoric acid obtained, from the reaction of phosphate rock with sulphuric acid, about four tons of phosphogypsum are produced. The level of radioactivity present in the phosphogypsum, among other impurities, prevents its reuse for a variety of purposes. Large quantities of phosphogypsum have been produced worldwide. In 2006, the annual production was estimated to be about 170 million tons. Brazilian annual production of phosphogypsum reaches 5.5 million tons. Brazil, like other countries that produce phosphate fertilizer, tries to find solutions for the safe applications of phosphogypsum, in order to minimize the impact caused by its disposal. Most of the worldwide phosphogypsum is stockpiled, posing environmental concerns. The monitoring of air and groundwater pollution, radon exhalation rate and direct exposure to gamma radiation for workers should be considered. The aim of this study is to evaluate the natural radionuclides content and the radon exhalation rate from phosphogypsum piles from Ultrafertil and Fosfertil fertilizer industries. Samples of this material were analyzed by gamma ray spectrometry for their radionuclide content. Radon exhalation rate was measured by the activated charcoal collector method. A theoretical model for radon exhalation calculation, suggested by UNSCEAR, was applied in order to corroborate the experimental results.     

Determination of the radon diffusion coefficient and radon exhalation rate in Moroccan quaternary samples using the SSNTD technique

Measurements have been made of radon (²²²Rn), release from diverse quaternary samples collected from different sediment deposits in the Errachidia and Beni-Mellal areas (Morocco). The radon diffusion coefficient as one of some important parameters of radon transport in the soil has been measured using solid state nuclear track detectors (SSNTD). Radon -activity, uranium content and radon exhalation rate have been determined in the studied samples. Uranium concentrations were found to vary from 0.14 to 9.52 ppm whereas the radon exhalation rate varied from 0.003 to 0.145 Bq^.m^-2.h^-1. A positive correlation has been found between radon exhalation rate and uranium content in the studied samples. The average radon diffusion coefficients were found to vary from (1.26±0.09)^.10^-6 m^2.s^-1 to (4.3±0.36)^.10^-6 m^2.s^-1. Furthermore, the correlation between ²²²Rn diffusion coefficient and porosity are also discussed.     

Natural radioactivity of building materials

Experiments were designed to measure trace uranium concentration and the rate of radon exhalation from masonry structural materials, both bare and surface finished and coated. LR115 cellulose nitrate track detectors were used to record the alpha emission from structural material surface. Fission track, neutron activation and fluorometric analysis methods were used to determine the uranium content. Most types of paints studied will reduce alpha contribution and radon emanation from building materials.     

Radon health hazards of some rocks of Iranian origin, frequently used as building stones

Radon exhalation rate from various types of stones, used inside the living buildings, is a major factor for evaluation of the environmental radon level. To verify the significance and lethal impacts of this unknown and obscure source of radiation upon the people around the world, the exhaled radon gas concentrations from the rocks, granodiorite, granite, limestone and aragonite, and the effect of their block sizes on the exhalation rate, have been studied. The block samples, collected from their ores, were transferred to plastic containers in which the CR-39 detectors could properly be placed and air tightened, for concentration measurements. The results show the radon concentration of 7.4 ± 0.8, 6.6 ± 0.6, 0.08 ± 0.02 and 0.09 ± 0.02 kBq m⁻³ for granodiorite, granite, limestone and aragonite, respectively. The corresponding annual dose values in a closed environment are: 186 ± 20, 166 ± 15, 2.5 ± 1 and 2 ± 1 mSv y⁻¹. These absorbed dose values indicate that granodiorite and granite when used inside the buildings could increase the risk of various cancers while aragonite and limestone have much lower risks and are recommended for use inside the buildings. The former ones when used in the closure areas remedial action should be implemented. The results do not show obvious dependence between the rock size of the samples and their radon exhalation rate.     

Long-term radon investigation in four selected kindergartens in different geological and climate regions of Slovenia

During a one year-and-a-half period in 1993 and 1994 indoor radon concentrations were measured with complementary measurement techniques in four selected kindergartens in different geological and climate regions in Slovenia. This study was performed to obtain more information how local geology, climate, building materials and occupational patterns affect radon concentration in a kindergarten. In addition, the advantages and disadvantages of different measurement techniques were critically appraised. It was found that average working hours radon concentrations, calculated on the basis of continuous radon measurements, are significantly lower than whole day averages obtained by track-etch detectors. The ratio might be as large as two.     

Simple and rapid methods for on-site determination of radon and thoron in soil-gases for seismic studies

The determination of soil-gas anomalies especially ²²²Rn anomalies, are important to precisely locate fault traces, as well as to investigate earthquake precursors. In this paper, we have studied and compared new rapid methods for on site determinations of radon (²²²Rn), thoron (²²⁰Rn) and total radon (²²²Rn+²²⁰Rn) in soil-gas. These new techniques pump the soil-gas continuously from the soil through a simple sampling tube to the counting cell for one-minute with discarding the excess. Then, either four one-minute counting periods (5-minute technique) or nine one-minute counting intervals (10-minute technique) are followed immediately. In all the methods, conversely to Morse"s method, the first counting period (C1) was not employed for calculations. Three calculation methods for the five-minute technique, two for the ten-minute technique and a modified Morse"s method are compared with theoretical values and different real soil-gases with different radon/thoron ratios. The affect of different flow rates of soil-gases into the counting cell was also investigated. Finally, the ten-minute technique seems to be a little more accurate, but the 5-minute technique is much more suitable for seismic field studies when a much larger number of determinations are required in a short time.     

Indoor radon risk potential of Hawaii

Summary A comprehensive evaluation of radon risk potential in the State of Hawaii indicates that the potential for Hawaii is low. Using a combination of factors including geology, soils, source-rock type, soil-gas radon concentrations, and indoor measurements throughout the state, a general model was developed that permits prediction for various regions in Hawaii. For the nearly 3,100 counties in the coterminous U.S., National Uranium Resource Evaluation (NURE) aerorad data was the primary input factor. However, NURE aerorad data was not collected in Hawaii, therefore, this study used geology and soil type as the primary and secondary components of potential prediction. Although the radon potential of some Hawaiian soils suggests moderate risk, most houses are built above ground level and the radon soil potential is effectively decoupled from the house. Only underground facilities or those with closed or recirculating ventilation systems might have elevated radon potential.     

Radioactivity contents in building materials used in Hong Kong

The radioactivity contents in building materials used in Hong Kong were measured to determine the sources of the high indoor radon concentrations observed in local buildings. The radium contents and the radon emanation coefficients of different building materials were measured by high resolution γ-ray spectroscopy using germanium detectors. The radon exhalation rates were measured using scintillation cells by circulating the exhaled radon from building materials and obtaining the initial growth rates. The radium content and the radon exhalation rates of concrete and bricks used in Hong Kong were found to be higher than those in some other countries, resulting in high indoor radon concentrations probably due to the high radioactivity contents in the aggregates, granitic in nature, used in building materials.     

Thoron interference in radon exhalation rate measured by solid state nuclear track detector based can technique

This paper presents the extent of thoron (²²⁰Rn) interference in the radon (²²²Rn) exhalation rate, measured by solid state nuclear track detector based ‘Can’ technique. Experiments were carried out following the standard procedure of ‘Can’ technique as well as active technique as a reference method for ²²²Rn and ²²⁰Rn exhalation measurements. It was found that ²²⁰Rn interference may lead to overestimation of ²²²Rn exhalation by a significant factor which can be as high as 12 depending upon the rate of ²²⁰Rn exhalation from samples.