222Rn Exhalation Rate Research Articles

Radon exhalation from granite countertops and expected indoor radon levels

Radon (222Rn) exhalation rates from granite countertops were measured using a continuous radon monitor. The countertops could be separated in three groups according to radon their exhalation rates. However, even for a worst-case scenario (e.g. E ~ 1.10 Bq m−2 h−1, no air circulation and full tile home) the contribution to indoor radon concentration is estimated to be [Rn] < 100 Bq m−3. In addition, despite the uneven radium distribution in the granite slabs, there is significant correlation (r 2 = 0.50) between the measured radon levels and the radium content of the granites.

A study on indoor radiation dose, radon, thoron and progenies concentrations in a hilly area

The background indoor gamma radiation in the residential places was estimated using CaSO4:Dy-based thermoluminescent dosimeters. The indoor gamma dose varied from 71 to 327 nGy h−1 with a mean value of 162 ± 31 nGy h−1. The highest gamma dose was observed in summer and the lowest in winter. The indoor gamma radiation was also found to vary with the type of house and building materials used. Indoor radon, thoron and progeny levels were measured for different types of dwellings during four seasons of a year using LR 115 type II film-based solid state nuclear track detectors loaded in twin chamber plastic cups. The average highest radon, thoron and progeny were observed during winter, and the corresponding lowest values were observed during summer. The concentrations of radon, thoron and progenies were found to vary with the type of houses and building materials used. The highest values were observed in mud houses, and the lowest values were recorded in wooden houses. This observed variation may be attributed to changes in ventilation conditions and exhalation rate of 222Rn and 220Rn from the floor and walls of the houses. The effective dose received by the general public due to indoor gamma radiation was found to be 0.79 mSv y−1 and the corresponding values due to radon, thoron were 1.02, and 0.54 mSv y−1, respectively. The inhalation dose received by the general public of the study area was found to be lesser than the action limit of International Commission on Radiological Protection (ICRP), 2009.

NORM, radon emanation kinetics and analysis of rocks-associated radiological hazards

Analysis of naturally occurring radioactive material (NORM) and environmental (radiological) hazard associated with radionuclides in rocks from northeastern Nigeria was carried out and the results are presented. NORMs analysis on rock samples was undertaken with gamma-ray spectroscopy, while radon isotopes were analyzed using an electric radon measurement device (RAD 7). Activity concentration (Bq kg−1) of 226Ra, 232Th and 40K ranges from 11.4 ± 2.6 to 74.6 ± 4.8, 26.6 ± 0.8 to 183.4 ± 3 and 30.1 ± 4.6 to 1120.3 ± 16.4, respectively. Ranges for annual effective dose (mSv) are 0.03–0.20; radium equivalent (Bq kg−1) is 5.7.33–358.36; external hazard index is 0.16–0.99; 222Rn and 220Rn exhalation rates (Bqm−3 h−1) are 2.60–6.25 and 0.50–7.10, respectively. For radon emanation coefficient, the working month level and related dosages ranges are 0.012–0.058, 0.25–0.00 and 1.38–3.30 mSv, respectively. The results reveal that the possible radionuclides enrichment in the rocks is potentially an environmental (radiation) hazard to the inhabitants of the area.

Determination of natural radioactivity, 222Rn and 220Rn exhalation rates and radiation hazards of fly ash and fly ash brick used in Baotou, China

Natural radioactivity levels, 222Rn and 220Rn exhalation rates and radiation hazards of fly ash and fly ash brick used in Baotou, China were determined. The activity concentrations of 226Ra, 232Th, and 40K in fly ash samples ranged from 38.81 to 93.73, 40.34 to 135.17, and 66.92 to 290.86 Bq/kg with an average of 76.52, 109.95, and 170.72 Bq/kg, respectively; while in fly ash brick samples, these radionuclides ranged from 42.43 to 71.60, 76.65 to 208.37, and 94.32 to 489.42 Bq/kg with an average of 53.83, 101.93, and 266.48 Bq/kg, respectively. The exhalation rates of 222Rn and 220Rn in all determined samples were in the range of 1.13-20.50 and 15.60-113.00 mBq/m2s, respectively. The calculated results of the radium equivalent activity, external hazard index, internal hazard index, indoor annual effective dose and outdoor annual effective dose indicated that fly ashes and fly ash bricks collected from some brick factories of Baotou would pose excessive radiation risks to inhabitants and that they are not suitable for use in building construction. The natural radioactivity level of fly ash and fly ash brick needs to be constantly monitored considering the radiation safety of the local residents.

A process-based &amp;lt;sup&amp;gt;222&amp;lt;/sup&amp;gt;radon flux map for Europe and its comparison to long-term observations

Abstract. Detailed 222radon (222Rn) flux maps are an essential pre-requisite for the use of radon in atmospheric transport studies. Here we present a high-resolution 222Rn flux map for Europe, based on a parameterization of 222Rn production and transport in the soil. The 222Rn exhalation rate is parameterized based on soil properties, uranium content, and modelled soil moisture from two different land-surface reanalysis data sets. Spatial variations in exhalation rates are primarily determined by the uranium content of the soil, but also influenced by soil texture and local water-table depth. Temporal variations are related to soil moisture variations as the molecular diffusion in the unsaturated soil zone depends on available air-filled pore space. The implemented diffusion parameterization was tested against campaign-based 222Rn soil profile measurements. Monthly 222Rn exhalation rates from European soils were calculated with a nominal spatial resolution of 0.083° × 0.083° and compared to long-term direct measurements of 222Rn exhalation rates in different areas of Europe. The two realizations of the 222Rn flux map, based on the different soil moisture data sets, both realistically reproduce the observed seasonality in the fluxes but yield considerable differences for absolute flux values. The mean 222Rn flux from soils in Europe is estimated to be 10 mBq m−2 s−1 (ERA-Interim/Land soil moisture) or 15 mBq m−2 s−1 (GLDAS (Global Land Data Assimilation System) Noah soil moisture) for the period 2006–2010. The corresponding seasonal variations with low fluxes in winter and high fluxes in summer range in the two realizations from ca. 7 to ca. 14 mBq m−2 s−1 and from ca. 11 to ca. 20 mBq m−2 s−1, respectively. These systematic differences highlight the importance of realistic soil moisture data for a reliable estimation of 222Rn exhalation rates. Comparison with observations suggests that the flux estimates based on the GLDAS Noah soil moisture model on average better represent observed fluxes.

Natural radioactivity and radon exhalation rates in man-made tiles used as building materials in Japan.

Man-made tiles frequently used in Japan were collected, and activity concentrations and radon ((222)Rn) exhalation rates in these tiles were measured. Dose estimations for inhabitants living in houses built using these tiles were also carried out. The activity concentrations of (226)Ra, (228)Ra and (40)K in the man-made tiles were 31-170, 35-110 and 260-980 Bq kg(-1), respectively. The (222)Rn exhalation rates in the tiles were 8.8-21 μBq m(-2) s(-1). The ranges of experimental activity concentrations and (222)Rn exhalation rates were almost identical to those of natural rocks used as typical building materials in Japan. The maximum value of effective dose to inhabitants living in houses built with the man-made tiles was 0.14 mSv y(-1), which is lower than the reference level range (1-20 mSv y(-1)) for abnormally high levels of natural background radiation published in the ICRP Publication 103.

Radon and Thoron Exhalation Rates from Surface Soil of Bangka - Belitung Islands, Indonesia

DOI:10.17014/ijog.2.1.35-42Radon and thoron exhalation rate from soil is one of the most important factors that can influence the radioactivity level in the environment. Radon and thoron gases are produced by the decay of the radioactive elements those are radium and thorium in the soil, where its concentration depends on the soil conditions and the local geological background. In this paper, the results of radon and thoron exhalation rate measurements from surface soil of Bangka Belitung Islands at thirty six measurement sites are presented. Exhalation rates of radon and thoron were measured by using an accumulation chamber equipped with a solid-state alpha particle detector. Furthermore, the correlations between radon and thoron exhalation rates with their parent nuclide (226Ra and 232Th) concentrations in collected soil samples from the same locations were also evaluated. The result of the measurement shows that mostly the distribution of radon and thoron is similar to 226Ra and 232Th, eventhough it was not a good correlation between radon and thoron exhalation rate with their parent activity concentrations (226Ra and 232Th) due to the environmental factors that can influence the radon and thoron mobilities in the soil. In comparison to a world average, Bangka Belitung Islands have the 222Rn and 220Rn exhalation rates higher than the world average value for the regions with normal background radiation.

A Study on Radon (222Rn) Exhalation Rate in the Rocks Used as Building Materials in Tiruchirappalli District, TN, India

Tiruchirappalli district is naturally endowed with rich building material resources, like stone, granite, sand, brick, cement etc. which are also used in the neighbouring districts. Hence, measurement of radon level in these building materials is important, because radon, a radioactive gas, is one of the major causative factors for human lung cancer and it is important to assess its impact on human health. The present study was undertaken to measure the activity concentrations of radon in 14 sedimentary rock (sand stone) quarries and 9 igneous rock (granite) quarries spread over Tiruchirappalli district. The Sealed Can Technique using Solid State Nuclear Track Detector (SSNTD) was employed for the measurement of radon emanation. The activity concentrations of radon in sedimentary rocks analyzed ranged from 13.2 - ±0.7 Bq m-3 to 218.0 - ± 10.6 Bq m-3 with the geometric mean activity level of 46.3 Bq m-3. However, radon concentrations in igneous rocks are distinctly higher than those of sedimentary rocks and ranged from 95.6 - ± 8.0 Bq m-3 to 1140 - ±95.0 Bq m-3 with the geometric mean activity concentration of 392.6±2.1 Bq m-3. The geometric mean radium concentration (CRa) recorded in both sedimentary (3.4 - ±2.3 Bq kg-1) and igneous rocks (50.2 - ±2.1 Bq kg-1) were well within the limit prescribed for dwellings (370 Bq kg-1). The mass and surface exhalation rates were also calculated in all the rock samples. The study concludes that the sedimentary rocks and the igneous rocks analyzed were radiologically safe (less than the permissible limit of 600 Bq m-3) when used as building materials except the granite rocks from Narthamalai (682 - ±57.3 Bq m-3) and Vilathupatti (1140.0 - ±121 Bq m-3).

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.

A method to simultaneously and continuously measure the 222Rn and 220Rn exhalation rates of soil in an open loop

This paper presents a process in which a radon monitor based on the electrostatic collection method is used to measure the 222Rn and 220Rn exhalation rates simultaneously and continuously employing a ventilation-type accumulation chamber. Generally, the radon exhalation rate can be measured by accumulation technique, but cannot be measured continuously. The advantage of this method using a ventilation-type accumulation chamber is that the radon exhalation rates can be measured continuously. Even though the environmental air is drawn into the chamber, the low atmospheric values of radon and thoron do not influence the measurement accuracy. The 222Rn and 220Rn exhalation rates error from the environmental air is less than 5% in this experiment.

Measurement of 222Rn Concentration and Exhalation Rate from Phosphate Rocks Using SSBD Detector in Saudi Arabia

The radon concentrations and exhalation rates of phosphate rocks samples were measured using a silicon surface barrier detector. In this study, samples were collected from different locations of phosphate mine in Northern Saudi Arabia. The radon concentrations varied from 17 ± 0.5 to 77 ± 1.3 Bq m−3, and the radon exhalation rates from these samples ranged from 0.1255 (0.024) to 0.5791 Bq m−2 h−1 (0.111 Bq kg−1 h−1. The annual effective doses varied from 0.429 to 1.943 mSv y−1. The data were compared with the global values of radon concentration.

Back diffusion correction for radon exhalation rates of common building materials using active measurements

The radioactivity content of various samples like soil and building materials are expressed in term of the activity concentration (Bq kg−1) of uranium, radium, thorium and potassium present in them and the radon (222Rn) exhalation rate. The radon exhalation rate is an important parameter for expressing the radioactive contents of materials used for building. The contribution of radioactive gas radon to inhalation dose can be measured by exhalation rate. The exhalation rates measured may be free or bound, the free exhalation rates of materials were calculated by initial slope of radon growth curve in closed chamber test. While the measurement of the bound exhalation rates of materials is difficult due to back diffusion and leakage. Thus it is necessary to measure these two parameters and correction should be made for free exhalation rates. The leakage rate was found to be (4.76 ± 0.14) × 10−3 h−1 (65 ± 2.1 cc h−1) for 13.7 L chamber and (6.32 ± 0.9) × 10−3 h−1 (216 ± 30 cc h−1) for 34.2 L chamber. The free exhalation rates of building materials varied from 0.25 ± 0.02 Bq m−2 h−1 for fired brick to 1.79 ± 0.05 Bq m−2 h−1 for concrete while the back diffusion rates showed maximum value (5.49 ± 0.2) × 10−2 h−1 for unfired brick and minimum (1.05 ± 0.14) × 10−2 h−1 for concrete samples. The back diffusion rates of the samples under study were also measured by direct fitting of radon growth data and were in good agreement with the measured values.

Activity Concentration of Natural Radionuclides and Radon and Thoron Exhalation Rates in Rocks Used as Decorative Wall Coverings in Japan

In Japan, many dwellings have decorative wall coverings made from granite, andesite, tuff, gabbro, and marble. However, information regarding activity concentrations and radon (Rn) and thoron (Rn) exhalation rates for such rocks is very scarce. Therefore, samples of the granite, andesite, tuff, and marble that are used as wall coverings in Japan were collected from mining companies, and their activity concentrations and Rn and Rn exhalation rates were measured. Dose estimations for inhabitants living in houses built with these materials were also carried out. The activity concentration of natural radionuclides in all the materials was lower than the critical values described by the International Atomic Energy Agency (IAEA) (10,000 Bq kg for K and 1,000 Bq kg for all other radionuclides of natural origin). The maximum values of Rn and Rn mass exhalation rates for the granite samples were 0.12 and 430 mBq kg s, and those for the area exhalation rates were 1.8 and 6300 mBq m s, respectively; these values are higher than those for other samples. The maximum value of effective doses to inhabitants was 0.68 mSv y, which is lower than the intervention exemption level (1 mSv y) given in the International Commission on Radiological Protection (ICRP) Publication 82.

Quantification of emission estimates of CO2, CH4 and CO for East Asia derived from atmospheric radon-222 measurements over the western North Pacific

ABSTRACTEmissions of CO, CH4 and CO2 in East Asia were estimated using the atmospheric concentration of 222Rn measured at Minamitorishima (MNM) and Yonagunijima (YON) with a high-precision 222Rn measuring system. The 222Rn measurements showed a distinct seasonal variation, as well as enhanced 222Rn (ERN) events associated with high-frequency synoptic variations. The enhancements of CO, CH4 and CO2 coincided with the ERN events at MNM and YON. The enhancement ratios ΔCH4/ΔRn, ΔCO2/ΔRn and ΔCO/ΔRn calculated for the ERN events and corrected for the radioactive decay of 222Rn during the transport were used to estimate the emissions of CO, CH4 and CO2 by multiplying a constant 222Rn exhalation rate of 1.0 atom cm−2 s−1 and the associated catchment area estimated by a 3D transport model. By modifying the categorisation of the sources, the 222Rn-derived emissions of CO2 and CH4 were found to be in agreement with the published emission databases. As for the CO emission, results of our study were consistent with the REAS CO emission database but showed that the EDGAR database underestimates the CO emission over East Asia by about 44%. It is demonstrated that the 222Rn tracer method used in this study could provide a useful and independent tool to verify the trace gas emissions in East Asia.

Radon exhalation and natural radiation exposure in low ventilated rooms

In the first part of this paper, the influence of radon (222Rn) exhalation rate from walls and air exchange upon its concentration in room air was considered using a simple mathematical room model. The exhalation rates have been determined in ten low ventilated rooms of ten villas in Jeddah city (Western Province) of Saudi Arabia. An electroprecipitation method has been applied for the determination of the 222Rn gas concentration in these rooms. The mean 222Rn gas concentration was found to be 46.80±8.80Bqm−3. The mean 222Rn exhalation rate was estimated to be 20.11±6.90Bqm−2h−1. The mean inhalation dose due to the exposure to 222Rn gas was calculated to be 1.18±2.30mSvy−1.The second part of this paper deals with a study of natural radionuclide contents of samples collected from the building materials of these rooms under investigations in part one. Analyses were performed in Marinelli beakers with a gamma spectroscopy system to quantify radioactivity concentrations. The collected samples revealed the presence of the uranium–radium (226Ra) and thorium (232Th) radioisotopes as well as 40K. The mean activity concentration of 226Ra, 232Th and 40K was determined to be 48.30±5.08, 43.90±5.63 and 223.90±7.55Bqkg−1, respectively. These activities amount to a radium equivalent (Raeq) of 125.96±15.90Bqkg−1 and to a mean value of external hazard index (Hex) of 0.34±0.04.

Anomalous change in atmospheric radon concentration sourced from broad crustal deformation: A case study of the 1995 Kobe earthquake

Abstract Before the Kobe earthquake, an anomalous increase in atmospheric Rn concentration was observed. By separating the measured concentration of atmospheric Rn into three components according to the distance from the monitoring station, the variation of Rn exhalation rate can be estimated for the respective area using the daily minimum and maximum concentrations. The mean rate of Rn exhalation gradually increased in an area of 20 km around the monitoring station, becoming five times higher than normal in the period between October 1994 and the date of the earthquake. This area had a large co-seismic displacement of up to 30 cm, which roughly corresponds to the crustal strain of 10−6-order, and it is considered the main source for the atmospheric Rn prior to the Kobe earthquake. Analyses revealed that the pre-seismic change in the atmospheric Rn concentration exhibited an anomalous pattern which would yield information on the spatial distribution of the mechanical response of the ground.

Natural Radioactivity and Radon Exhalation in Phosphate Fertilizers

238U, 232Th, 226Ra, 222Rn and 40K activity concentrations in fertilizer samples collected from a local market were determined. Radon activity concentrations ranged from 0.04–252 Bq kg−1 and were comparable with low activity concentrations ranges reported previously. Radon exhalation rates and effective 226Ra concentration were determined using CR-39 solid-state nuclear track detectors. Effective 226Ra concentrations ranged from 4.27–33.93 Bq kg−1. Two different 222Rn exhalation rates were determined; area dependent exhalation rates (0.044–0.351 Bq m−2 h−1) and mass dependent exhalation rates (0.023–0.180) Bq kg−1 h−1). Even without secular equilibrium, strong correlations were generally apparent among uranium concentrations, effective 226Ra concentrations and 222Rn exhalation rates in samples with high concentrations of uranium. 232Th and 40K concentrations ranged from 0–44.6 and 0.08–127 μg/g, respectively.

TransCom continuous experiment: comparison of &amp;lt;sup&amp;gt;222&amp;lt;/sup&amp;gt;Rn transport at hourly time scales at three stations in Germany

Abstract. Fourteen global atmospheric transport models were evaluated by comparing the simulation of 222Rn against measurements at three continental stations in Germany: Heidelberg, Freiburg and Schauinsland. Hourly concentrations simulated by the models using a common 222Rn-flux without temporal variations were investigated for 2002 and 2003. We found that the mean simulated concentrations in Heidelberg are related to the diurnal amplitude of boundary layer height in each model. Summer mean concentrations simulated by individual models were negatively correlated with the seasonal mean of diurnal amplitude of boundary layer height, while in winter the correlation was positive. We also found that the correlations between simulated and measured concentrations at Schauinsland were higher when the simulated concentrations were interpolated to the station altitude in most models. Temporal variations of the mismatch between simulated and measured concentrations suggest that there are significant interannual variations in the 222Rn exhalation rate in this region. We found that the local inversion layer during daytime in summer in Freiburg has a significant effect on 222Rn concentrations. We recommend Freiburg concentrations for validation of models that resolve local stable layers and those at Heidelberg for models without this capability.

Natural radioactivity levels of limestone rocks in northern Iraq using gamma spectroscopy and nuclear track detector

The activity concentration of radionuclides, such as 238U, 226Ra and 40K of limestone rocks in northern Iraq was measured using gamma spectroscopy. The radionuclide activities were obtained and discussed. CR-39 nuclear track detector was used to measure the radon exhalation rates as well as the effective radium contents of these samples and are found to correspond with uranium concentration values measured by NaI(Tl) detector in the corresponding limestone rocks samples. The absorbed gamma dose rates in air due to the presence of 238U, 226Ra, 40K and cosmic ray contribution varied between 105.3 and 223.11 nGy/h. The annual effective dose of each sample has been calculated. The correlation between activities of 226Ra, 222Rn exhalation rates and 238U is explained. Results show a symmetrical distribution of activity concentrations of primordial of radionuclides in selected samples. The values of all studied radionuclides are considered to be a typical level of natural background and compared with results of similar investigations carried out else where.

INFLUENCE OF THE POROSITY ON THE 222RN EXHALATION RATE OF CONCRETE

The composition of 23 concrete mixtures was varied in five separate series to evaluate the influence of porosity on the ²²²Rn exhalation rate. In each series, a range in porosities is obtained by varying (1) the amount of cement, (2) type of cement (Portland or blast furnace slag cement), (3) the amount of water at a fixed cement level, (4) addition of an air entraining agent, or (5) the amount of recycled aggregates. The porosities ranged from 1% to 16%. The ²²²Rn exhalation rate is normalized to the ²²⁶Ra activity concentration and expressed as the ²²²Rn release factor to eliminate the effect of differences in ²²⁶Ra activity concentrations among the various concrete mixtures. Since most ²²²Rn originates from the cement, a ²²²Rn release factor based on the amount of ²²⁶Ra introduced by the cements appeared to be more adequate. Although the methods to attain the porosities in the concrete mixtures differ widely, this cement-related factor corresponds well with the capillary porosity of the mixtures. Since the water-to-cement ratio of the fresh paste is a good indicator of the capillary porosity, this is the guiding factor in the fabrication of concretes low in ²²²Rn exhalation. The lower the water-to-cement ratio, the less capillary pore area will be available from which ²²²Rn can emanate from the mineral matrix into the pore system. The good correlation between the cement-based ²²²Rn release factor and literature data on the internal capillary pore area support the results of this study.