Exhalation Rate Research Articles

Assessment of soil gas radon migration and transport through the estimation of radon diffusion length and diffusion coefficient in the soil matrix

Naturally occurring radioactive gas, radon is a decay product of radium present in the soil. Radon flux reaches the atmosphere through exhalation from soil surface. This study aims to estimate the radon diffusion length and diffusion coefficient in soil matrix on the premises of HNB Garhwal University campus at Tehri Garhwal, India. Soil gas radon concentration was measured at different depths (15, 30, 45, 60, 75, and 90 cm) using a Smart RnDuo (Scintillation-detector) at 14 different locations in the university campus. Simultaneous measurement of surface and mass exhalation rates was also carried out for each location. Gamma-ray spectrometry was used to estimate the radium content in soil samples. Results of the present study suggest that soil gas radon concentration increases with increasing sampling depth. The diffusion coefficient and length were calculated using the soil gas radon concentration gradient within the soil matrix. The average value of diffusion length (l) and diffusion coefficient (D) were obtained as, ls = 0.70 ± 0.22 m, Ds = 0.0054 ± 0.0049 m2 sec-1 and la = 0.77 ± 0.63 m, Da = 0.0073 ± 0.014 m2 sec-1 by Fick’s diffusion model and analytic models, respectively.

Effect of temperature on the radon release characteristics of red clay

Bricks and tiles crafted from fired red clay are extensively utilized in everyday construction activities. However, red clay inherently contains radon gas, a radioactive substance that could potentially endanger human health. Hence, investigating the radon emission patterns of red clay post high-temperature treatment holds significant importance. This study examines the pore structure of red clay following high-temperature treatment through nitrogen adsorption and analyzes the radon release patterns. Findings reveal that the radon release rate from red clay initially rises, then declines with increasing temperature, peaking at 200 °C, registering at 0.0127 Bq/(m2 s). The pore structure significantly influences radon exhalation, with connectivity and micropore volume demonstrating linear correlations with radon exhalation rate, with correlation coefficients of 0.96 and 0.78, respectively. This research offers valuable insights into radon radiation in structures made of red clay.

Radiation protection and natural building materials in cultural heritage

IntroductionBuildings that constitute cultural heritage and that are the identity of a defined geographical area are increasingly being restored to offer the community historical places to enjoy. Often the restoration preserves the original structure and building materials, which are usually natural stones. In this study, a radioprotection protocol dedicated to this kind of built environment was proposed and validated.MethodsAfter identifying the two predominant types of building material stones (Rosso ammonitico and Pietra Serena), radiometric measurements for natural gamma-emitting radionuclides (Ra-226, Th-232, and K-40) and measurements of the emanation coefficient and calculation of the exhalation rate of radon gas were carried out.ResultsThe two types of stone have a content of natural radionuclides that do not exceed the levels recommended by the regulations. The difference between the two types of stone is of an order of magnitude indicating that the red ammonite has a greater radiological impact than the pietra serena.DiscussionThe results, in addition to ensuring the radioprotection of the population, highlighted the need to increase the number of this kind of investigations to implement scientific knowledge and serve the stakeholders involved.

Investigation of radon and thoron exhalation rates in soils: Manali-Leh Highway region of Himalayas

This study analyses the natural radionuclides concentration (226Ra and 232Th) along with the radon and thoron exhalation rates in 50 soil samples collected from the Manali-Leh Highway region of the Himalayas. The specific activity of 226Ra and 232Th radionuclides was determined using a NaI(Tl) detector, revealing that the concentration values of these radionuclides are lower than the global average. The radon and thoron exhalation rates in the soil samples were measured utilizing a SMART RnDuo detector. The radon mass exhalation rates range from 6 to 87 mBq kg−1 h−1, with average values of 25 mBq kg−1 h−1. The thoron surface exhalation rates vary from 110 to 757 Bq m−2 h−1, with a mean value of 385 Bq m−2 h−1. Additionally, the emanation coefficient and alpha dose equivalent for radon were calculated and the correlation between parent and daughter radionuclides was also explored.

Assessing Radon Exhalation Rates from Building Tiles: Implications for Sustainability and Indoor Air Quality

Assessing Radon Exhalation Rates from Building Tiles: Implications for Sustainability and Indoor Air Quality

Radiation doses assessment and radon exhalation rate from the soils of Albyda area, Yemen

This work focuses on evaluating the potential health hazards posed by natural radionuclides in soil samples collected from 20 different sites in the Albyda area, Yemen. The activity concentrations of 226Ra, 232Th and 40K and radon exhalation rates in the soil samples were investigated. Alpha GUARD detector was used to estimate 222Rn concentration, while activity levels for natural radionuclides were measured by HPGe detector. The average values obtained for 226Ra, 232Th, and 40K were 27.60 ± 2.40 Bq/kg, 35.07 ± 2.45 Bq/kg, and 544.71 ± 48 Bq/kg, respectively, and for 222Rn concentrations were 135 ± 15 Bq/m3. Our findings show that the concentrations of radionuclides were within the limits of the world average established by UNSCEAR, except the concentrations of 40K, which was slightly higher than the world average (420 Bq/kg), while the average 222Rn concentration was lower than the ICRP reference level of 300 Bq/m3, and the average area exhalation rate 3.46 × 10−5 Bq m−2 s−1 was lower than the UNSCEAR world average of 0.016 Bq m−2 s−1. Therefore, the soil in this study does not pose any radiological hazard to the population due to the harmful effects of ionizing radiation. The results of the current study highlight the potential health hazard posed by radon and radioactivity levels in the soil samples from Albyda area, Yemen, which will help to increase awareness of the radiological hazard and the data could also be used as a reference for future research on radioactivity mapping in the study area.

Measuring the real radon exhalation from walls in buildings

Building materials may significantly contribute to indoor radon activity concentration. Measuring the radon exhalation rate directly on the existing building elements represents the most accurate and reliable method to assess the building materials’ contribution. However, due to the method’s inner difficulties, no specific apparatus has been developed and documented in the literature.An innovative apparatus has been designed, constructed, and commissioned to measure the radon exhalation rate in situ from vertical surfaces of existing building walls. The apparatus is non-destructive, completely self-standing, and easily transportable. The sealing mechanism has been demonstrated to assure airtightness similarly to destructive setups. The measurements’ repeatability is less than 10% at different radon exhalation rates.The apparatus introduced is the only available solution to measure the site-dependent contribution of building materials to the indoor radon concentration. The apparatus allows for improving the specificity, so the effectiveness, of the remedial interventions to reduce the radon-related health risk.

Radiological characterization of materials used in the Italian heritage buildings

Building materials (BMs) can cause significant gamma dose indoors due to their natural radionuclide content. In 2013, the European Directive 59/2013/EURATOM introduced, in annex XIII, a list of types of BMs of interest for the content of gamma-emitting radionuclides among which materials or additives of natural igneous origin, such as granitoids, tuff and lava, are included. These materials have been largely employed for decorative and structural purposes in the course of centuries in the Italian heritage buildings. Aim of this study is to assess the contribute of BMs in terms of alpha exposure. Six samples of different materials, characterized in a previous study by the authors in terms of radiological content by means of a gamma spectrometry, have been analyzed in order to determine the specific exhalation rate of 222Rn, the radon emanation coefficient and excess in indoor radon concentration. Results confirm that BMs of natural igneous origin can play an important role in terms of alpha radiation dose and internal exposure due to the inhalation of the alpha particles emitted.

Study on the radon exhalation rate of phyllite under thermal effects

As a result of human underground mining activities, phyllite has been extensively reused to make raw ceramic materials and concrete aggregates. Building materials are a significant source of indoor radon, and radon gas emitted from phyllite poses radiation risks to humans. High temperatures can alter the structural properties of rocks, impacting radon exhalation. Thus, this study examined phyllite's radon exhalation rate after heat treatment ranging from 25 °C to 1000 °C. The effects of changes in pore structure and mineral composition on phyllite's radon exhalation were analyzed in detail using nuclear magnetic resonance (NMR), polarizing optical microscopy (POM), three-dimensional microscopy (3DM), and scanning electron microscopy (SEM). Results indicate that the radon exhalation rate initially increases and then decreases with rising temperature. This rate correlates positively with both total porosity and micropore porosity. Processes such as free water evaporation, pyrite oxidation, quartz phase transformation, and chlorite dehydroxylation within phyllite contribute to pore development and the movement of free radon within pore spaces. The highest total porosity and radon exhalation rate occur at 700 °C, measuring 8.6 % and 6.14 Bq/m2·h, respectively—4.30 times and 1.18 times higher than at 25 °C. Additionally, mineral decomposition and melting reduce pore connectivity and effective porosity, hindering radon migration. These findings offer guidance for assessing radon radiation risks and indoor radon potential in phyllite-based building materials.

Measurement and mapping of radon exhalation rate around the uranium mines in Sikar, Rajasthan, India

Measurement and mapping of radon exhalation rate around the uranium mines in Sikar, Rajasthan, India

Laboratory study on the relationship between the vertical distribution of radon concentration in soil and the exhalation rate of radon from the soil surface

Laboratory study on the relationship between the vertical distribution of radon concentration in soil and the exhalation rate of radon from the soil surface

Characteristic parameters and radon exhalation rates of aerated concrete blocks

ObjectiveTo understand the characteristic parameters and radon exhalation rates of aerated concrete blocks. MethodsA total of 39 nationally inspected samples were measured. Their dry density was determined based on their mass and volumes, their porosities were measured on the principle of volumetric expansion, and their radium content was determined using a high-purity germanium (HPGe) detector for gamma-ray spectroscopy. Furthermore, their diffusion lengths were quantified by establishing a combined cumulative and diffusion chamber, and their radon exhalation rates were measured through closed-box testing using a continuous radon monitor. ResultsThe aerated concrete blocks exhibited dry densities ranging from 464 to 840 ​kg/m3 [average: (654.0 ​± ​82.5) kg/m3], open porosities from 67.1 ​% to 81.1 % [average: (74.3 ​± ​3.3) %, radium (226Ra) content from 12.3 to 136 Bq/kg [average: (63.0 ​± ​30.4) Bq/kg], diffusion lengths from 0.49 to 1.01 ​m [average: (0.70 ​± ​0.15) m], and radon exhalation rates from 0.6 to 22.8 Bq·m−2·h−1 [average: (7.3 ​± ​5.3) Bq·m−2·h−1]. ConclusionAerated concrete blocks exhibit significantly higher porosities, diffusion lengths, and radon exhalation rates than traditional concrete and clay bricks. These blocks might contribute to the high indoor radon concentration observed in modern buildings in China.

Radon exhalation rate from the latex pillows and its potential exposure to users

ObjectiveTo develop a new system to accurately measure the radon exhalation from the latex pillows, and to estimate its potential exposure to users. MethodsThe new system is composed of two loops, the first loop is designed to trap background radon and thoron until their levels are nearly zero, and the second loop is the measurement loop to detect radon and thoron exhalation rates from the pillows. ResultsThe results showed that mass radon exhalation rated ranged from 0.18 Bq·kg−1⋅h−1 to 0.78 Bq·kg−1⋅h−1, with an average of (0.36 ​± ​0.17) Bq·kg−1⋅h−1 in the 9 samples. The average annual effective dose to users in a model room was estimated to be (15.51 ​± ​12.69) μSv by assuming two pillows was used. These results demonstrate that the new system can effectively measure radon exhalation rates in latex pillows, and the potential exposure to radon exhalating from the pillows is very low.

Radon exhalation and emanation assessments in the Transdanubian Central Mountain in Hungary

ObjectiveTo determine the radium-226 activity concentration, the massic radon exhalation rate and emanation factor of 55 soil samples from the Central Transdanubian Mountains in Hungary as well as possible radon exhalation hotspots in the sampling area were determined. Further indoor measurements are planned to investigate the possible exposure to radon of the inhabitants. MethodsThe radium-226 activity concentration measurements were carried out with a semiconductor HPGe gamma-ray spectrometer. The massic radon exhalation rate and emanation factor were determined by measuring the radon activity concentrations using the accumulation method with a system developed by our department based on an AlphaGUARD DF2000 portable radon monitor. ResultsThe activity concentrations of radium-226 were between (11.4 ​± ​2.5) and (118.2 ​± ​3.0) Bq/kg, while their average was 39.51 Bq/kg. The massic radon exhalation rates were between (1.02 ​± ​3.64) mBq⋅kg−1⋅h−1 and (275.63 ​± ​4.05) mBq⋅kg−1⋅h−1, while their average was 39.51 mBq⋅kg−1⋅h−1. Finally, the emanation factors were between (0.01 ​± ​0.04) and (0.80 ​± ​0.03) with an average of 0.30. ConclusionsIn our study, the results recorded from the bedrock at the sampling sites were analyzed. 9 samples were taken from sites comprised of limestone bedrock, moreover, the average radium-226 activity concentrations and massic radon exhalation rates at these sampling sites were higher than average. It was also concluded that although no regional correlation can be seen from the results, a possible smaller radon hotspot was identified from our measurements where further sampling will be carried out.

Radon Gas Detection of Soil Samples in Primary Schools at Najaf City, Iraq

Abstract: The radon concentration, specific activity of 226Ra (CRa), and 238U concentrations (CU) in soil samples from 100 primary schools of Al-Najaf province, Iraq, were measured to determine the safety of students and staff using the CR-39 nuclear track detector based on the sealed can technique. The mean values of 222Rn concentration in the air space of the container (C) and the soil sample (CRn) were 23.53±1.149Bq/m3 and 960.38±47 Bq/m3, respectively. The mean values of CRa and CU were 0.035±0.002 Bq/kg and 0.043±0.002 ppm, respectively. The 222Rn,226Ra, and 238U concentrations were lower than the worldwide level. Radiological parameters such as annual effective dose (AED) and radon exhalation rate per unit mass (EM) and per unit surface (ES) also were determined. The results indicate normal levels for these parameters, except for higher values of AED in some primary schools, according to UNSCEAR data. Keywords: Radon, CR-39 detector, Soil of primary schools, Al-Najaf province.

Response surface prediction model of radon exhalation rate on beach surface of uranium tailings pond based on single factor law

Response surface prediction model of radon exhalation rate on beach surface of uranium tailings pond based on single factor law

Assessment of the Radioactivity, Metals Content and Mineralogy of Granodiorite from Calabria, Southern Italy: A Case Study.

In this paper, an assessment of the natural radioactivity level, radon exhalation, metal contamination, and mineralogy of a granodiorite rock sample from Stilo, in the Calabria region, Southern Italy is presented as a case study. This rock was employed as a building material in the area under study. The specific activity of 226Ra, 232Th and 40K natural radioisotopes was assessed through high-purity germanium (HPGe) gamma-ray spectrometry. Then, several indices such as the absorbed gamma dose rate (D), the annual effective dose equivalent (AEDE), the activity concentration index (ACI) and the alpha index (Iα), were quantified to determine any potential radiological health risk related to radiation exposure from the analyzed rock. Furthermore, E-PERM electret ion chambers and inductively coupled plasma mass spectrometry (ICP-MS) measurements were carried out to properly quantify the radon exhalation rate and any possible metal pollution, respectively. In particular, to further address metal pollution factors, the geo-accumulation index (Igeo) was calculated to properly address the toxicity levels of the ecosystem originating from the detected metals. Finally, with the aim of successfully discriminating the provenance of such naturally occurring radionuclides, a combined approach involving X-ray diffraction (XRD) and µ-Raman spectroscopy was employed for the identification of the main radioisotope-bearing minerals characterizing the investigated granodiorite. The results achieved in this case study can be taken as the basis for further inquiries into background levels of radioactivity and chemical contamination in natural stone employed as building materials.

Evaluation of accurate measurement methods for radon exhalation rate with advection effect and application in field

In decommissioning of a uranium tailings pond, radon exhalation rates on a beach surface should meet regulatory standards. Accurate measurements of the radon exhalation rate are demanded. However, current studies fail to consider the impact of advection under temperature variations or pressure gradients caused by gas movement on measurements using an accumulation chamber. Two proposed methods were therefore evaluated to accurately measure radon exhalation rates on the loose medium surface under advective conditions. Repeated experiments were conducted on a laboratory experimental platform filled with uranium tailings sand under advective flow rates of 0.03 and 0.3 L/min to validate the stability and reliability. Deviations between measured and true values were 0.1–6.1 % and 6.3–29.2 % for the two methods, respectively. Subsequently, numerical simulation was used to analyze defects of traditional methods and mechanisms of the new methods. In a field study, all methods were compared, and a predictive map of radon exhalation rates was created using interpolated data from 20 random sites using the new method. Results from the proposed methods, compared with traditional ones, were closer to true values under advective conditions, and accurate assessment of beach surface treatment was expected.

A study of 222Rn/220Rn exhalation rate and indoor 222Rn/220Rn levels in higher Himalayan terrain.

The noble radioactive gas radon and its isotope thoron dominate terrestrial radiation in the indoor environment. These gases eventually disintegrate generating radioactive ions that readily adhere to aerosol particles. This study was conducted in a tectonically active location with significant radon concentrations. The obtained average values of radon mass exhalation and thoron surface exhalation rate from this study are higher than the global average values of 56 mBq kg-1h-1 and 1000 mBq m-2s-1, respectively. As the exhalation rates are higher, naturally the average radon and thoron concentrations are also greater than the worldwide average values of 40 and 10Bqm-3, respectively. No significant correlation was observed between 222Rn and 220Rn exhalation rate and indoor 222Rn/220Rn concentration. The exposure dose due to 222Rn, 220Rn and their progenies shows no significant health risk.

Measurements of radon exhalations and radiological doses using LR-115 (II) nuclear track detectors in Tiru region of the Naga Schuppen Belt, India.

In this present study, the nuclear track detector LR-115 (II) was employed to assess radon (222Rn) exhalation rate, effective radium (226Ra) content, and the annual effective dose from coal and soil samples collected in and around the coal mining area of Tiru region of Nagaland, India. The 222Rn mass and surface exhalation rates and 226Ra contents were found to be in the ranges of 7.3-17.3 mBq kg-1 h-1, 242.9-573.6 mBq m-2h-1 and 1.0-2.3Bqkg-1, respectively, for coal and 15.8-22.0 mBq kg-1 h-1, 523.8-730.4 mBq m-2h-1 and 2.1-2.9Bqkg-1, respectively, for soil. The 222Rn exhalation rates and 226Ra contents in soils were found to be higher than in coal. The estimated annual effective doses for coal and soils were found to be in the ranges of 17.6-41.6 and 38.0-53.0μSv y-1, respectively. This study is an important contribution to the understanding of radiation exposure in the coal mining area of the thrust-bound sedimentary sequence of the Naga Schuppen Belt, and it would have potential impact on further human health studies. However, the measured values for all the samples were found to be within the globally recognised permissible range.