Emanation Rate Research Articles

A high-sensitivity radon emanation detector system for future low-background experiments

Radioactive radon atoms originating from the primordial 238U and 232Th decay chains are constantly emanated from the surfaces of most materials. The radon atoms and their radioactive daughter isotopes can significantly contribute to the background of low-background experiments. The 222Rn progeny 214Pb, for example, dominates the background of current liquid xenon-based direct dark matter detectors. We report on a new detector system to quantify the 222Rn surface emanation rate of materials. Using cryogenic physisorption traps, emanated radon atoms are transferred from an independent emanation vessel and concentrated within the dedicated detection vessel. The charged radon daughter isotopes are collected electrostatically on a silicon PIN photodiode to spectrometrically measure the alpha decays of 214Po and 218Po. The overall detection efficiency is ∼ 36 % for both polonium channels. The radon emanation activity of the emanation vessel was measured to be (0.16± 0.03) mBq, resulting in a detection sensitivity of ∼ 0.06 mBq at 90 % C.L.

Characterization of a 220Rn source for low-energy electronic recoil calibration of the XENONnT detector

Low-background liquid xenon detectors are utilized in the investigation of rare events, including dark matter and neutrinoless double beta decay. For their calibration, gaseous 220Rn can be used. After being introduced into the xenon, its progeny isotope 212Pb induces homogeneously distributed, low-energy (<30 keV) electronic recoil interactions. We report on the characterization of such a source for use in the XENONnT experiment. It consists of four commercially available 228Th sources with an activity of 55 kBq. These sources provide a high 220Rn emanation rate of about 8 kBq. We find no indication for the release of the long-lived 228Th above 1.7 mBq. Though an unexpected 222Rn emanation rate of about 3.6 mBq is observed, this source is still in line with the requirements for the XENONnT experiment.

Radiometric analysis of Brazilian commercial ornamental stones

The term “commercial ornamental stones” comprises different natural stones with different mineralogical components and the distribution and amount of natural radionuclides depended on the mineralogy. Few studies on natural radioactivity in ornamental stones carried out in Rio de Janeiro (Brazil) and the present work were carried out in order to analyze the distribution of activity concentration in these materials. The activity concentration of 238U, 235U, 226Ra, 232Th and 40K in Ornamental Stones measured using γ-ray spectrometry to estimate the radiation hazard as well as establishing a database for radioactivity levels. Samples were collected in stores in Rio de Janeiro, carefully transported, weighed, packed with PVC film and left to rest for at least 45 days to reach secular equilibrium. Samples analyzed by gamma spectrometry using a hyper pure germanium detector (HPGE). Detection efficiency for each sample was obtained using LabSOCS software. The activity concentrations for samples were within the ranges (0.83 ± 0.15 to 39.96 ± 1.19, 8.04 ± 2.54 to 111.36 ± 13.33, 0.43 ± 0.03 to 264.58 ± 0.98, BDL to 8.17± 0.65 and 1.30 ± 0.57 to 1567.01 ± 65.08) Bq⋅kg−1 for 238U, 226Ra, 232Th, 235U and 40K, respectively. The world average for building materials is 50 Bq⋅kg−1 for 238U, 50 Bq.kg−1 for 232Th and 500 Bq⋅kg−1 for 40K. In the present work, the average for granite was 19.43 ± 0.39 Bq⋅kg−1 for 238U, 56.70 ± 1.13 Bq⋅kg−1 for 232Th and 1113.28 ± 20.27 Bq⋅kg−1 for 40K, thus the values for 232Th and 238U are above the world average. Analyzing for the granite that showed the highest concentrations of activity the average values of Transport Rate was 3.12 ± 0.04 Bq⋅m−2⋅s−1, Emanation Rate was 0.16 ± 0.00 Bq⋅kg−1⋅s−1, Exhalation Flow was 530.26 ± 6.05 Bq⋅m−3, Effective Equivalent Dose Due to Radon Exposure was 0.78 ± 0.01 WLM⋅year−1 and Annual Effective Dose Due to Radon and Thoron was 7.02 ± 0.10 mSv⋅year−1. Annual Effective Dose Due to Radon and Thoron it is above the annual limit for public individuals which is 1 mSv⋅year−1 and below the occupationally exposed individual, which is 20 mSv⋅year−1 in an average of 5 years, it does not exceed the maximum level recommended by ICRP-60.

Radon Gas Estimation from Building Materials

Radon gas originating from building materials is generally thought to cause low concentration. Investigation and estimation of radon levels originating from building materials are important in terms of public health due to the use of dense concrete in tunnel form type houses, which is a building type widely used in Turkey, even though a significant part of Turkey is an earthquake zone. In this article, the effects of different parameters such as 238U concentration in building materials, diffusion constant of building elements, emanation rate, and ventilation rate on radon gas concentration are investigated. As a result, it is concluded that in some cases (such as high diffusion coefficient and insufficient ventilation rate) in houses built with tunnel form concrete structures, the radon level arising from building materials can reach a level that cannot be neglected.

Measurements of Radiometric Concentrations for &lt;sup&gt;222&lt;/sup&gt;Ra, &lt;sup&gt;238&lt;/sup&gt;U, &lt;sup&gt;232&lt;/sup&gt;Th and &lt;sup&gt;40&lt;/sup&gt;K in Soil Samples from Two Uranium Mines’ Stockpiles, Erongo Region, Namibia

&lt;p&gt;The continuous exposures from radiations to human population has led to research studies on evaluating the radioactivity concentrations in most parts of the world. Naturally occurring radioactive materials (NORM) have been greatly regarded as the chief sources of both terrestrial and cosmological radiations. In this study a high-purity germanium well detector was used to measure the activity concentrations of samples from mines 1 and 2 considered in the study. The measured average activity concentration for &lt;sup&gt;226&lt;/sup&gt;Ra, &lt;sup&gt;238&lt;/sup&gt;U, &lt;sup&gt;232&lt;/sup&gt;Th and &lt;sup&gt;40&lt;/sup&gt;K in mine 1 were estimated at 2546±10, 557±13, 215±2 and 1079±26 Bq.kg&lt;sup&gt;-1&lt;/sup&gt;, respectively. For mine 2, the estimated average values of the radionuclides of &lt;sup&gt;226&lt;/sup&gt;Ra, &lt;sup&gt;238&lt;/sup&gt;U, &lt;sup&gt;232&lt;/sup&gt;Th and &lt;sup&gt;40&lt;/sup&gt;K were calculated as 4414±27, 842±29, 436±5 and 2225±52 Bq.kg&lt;sup&gt;-1&lt;/sup&gt;, respectively. The high concentration of radium in samples contributed to high rate of radon emanation into the atmosphere, ground and surface water as well and, if no remedial measures are put in place, this may contribute to plants, animals and eventually human exposures in the region. The study concludes that mine tailings contribute to an increase in background radiation in the environment due to the fact that they are uncovered and deposited in the open environment, resulting in wind-blown &lt;sup&gt;226&lt;/sup&gt;Ra carrying dust entering nearby residential dwellings. The exposures rates could also be increased by other possible transfer pathways, such as ingestions, inhalations and external gamma radiations. Mining companies are urged to decrease windblown atmospheric exposure by using water tanks mounted on mining equipment to sprinkle on top of the soil or covering the tailings with canvas sheet.&lt;/p&gt;

Metrology infrastructure for radon metrology at the environmental level

Since 2020 a large consortium has been engaged in the project EMPIR 19ENV01 traceRadon to develop the missing traceability chains to improve the sensor networks in climate observation and radiation protection. This paper presents results in the areas of: Novel 226Ra standard sources with continuous controlled 222Rn emanation rate, radon chambers aimed to create a reference radon atmosphere and a reference field for radon flux monitoring. The major challenge lies in the low activity concentrations of radon in outdoor air from 1 Bq∙m-3 to 100 Bq∙m-3, where below 100 Bq∙m-3 there is currently no metrological traceability at all. Thus, measured values of different instruments operated at different locations cannot be compared with respect to their results. Whin this paper, new infrastructure is presented, capable of filling this gap in traceability. The achieved results make new calibration services, far beyond the state of art, possible.

Production and characterization of a 222Rn-emanating stainless steel source

Precise radon measurements are a requirement for various applications, ranging from radiation protection over environmental studies to material screening campaigns for rare-event searches. All of them ultimately depend on the availability of calibration sources with a known and stable radon emanation rate. A new approach to produce clean and dry radon sources by implantation of 226Ra ions into stainless steel has been investigated. In a proof of principle study, two stainless steel plates have been implanted in collaboration with the ISOLDE facility located at CERN. We present results from a complete characterization of the sources. Each sample provides a radon emanation rate of about 2 Bq, which has been measured using electrostatic radon monitors as well as miniaturized proportional counters. Additional measurements using HPGe and alpha spectrometry as well as measurements of the radon emanation rate at low temperatures were carried out.

Radon emanation from dust of varying composition and size

222Rn emanating from environmental dust constitutes an important background component for many low-energy, low-rate experiments. Radon emanation rates from dust and rock, thus, are important for experiment planning. In this paper, we report measured radon emanation fractions for five types of dry dust differing in grain size and composition. These data were obtained by a novel technique in γ-spectroscopy, measuring emanated and non-emanated 222Rn progeny activities as well as the parent 226Ra activity in a time series. The range of observed radon emanation fractions is (3.7 ± 2.0)% to (16.2 ± 0.9)%. Four of the five samples are standardized samples available commercially, so additional investigations of these samples may be readily carried out.

Quantification of the dependence of the emanation of radon from water on the pH and temperature of water

Uranium- and thorium-series isotopes are able to dissolve in hot spring waters and decay into radon, which could potentially cause health risk of the public. Besides, several environmental investigations can be carried out by measuring radon concentrations in hot spring waters. Accordingly, the measurement of radon in hot spring water is a significant issue.A practical method for measuring radon in hot spring water was developed by using a silicon semiconductor detector, RAD-7. The overall effect of detection efficiency and radon leakage of the measuring system were examined to calibrate the measured concentration of radon in hot spring waters. In addition, the effect of water temperature and pH on emanation of radon from standard 226Ra solutions as well as that of the measuring time on precision of the measurement were investigated. The correlation among temperature, pH and emanation of radon was then obtained. Further, the established method was applied to in-situ measurement to investigate the concentration of radon in hot spring waters from different geological areas in Taiwan.According to the percent error of the measurement, the measuring time for environmental samples was set as 50 min. The overall effect of radon leakage and detection efficiency of the measuring system was estimated to be 99.19 ± 7.47% with a standard rock source of 222Rn from NIST. Standard sources of 222Rn were prepared from 226Ra standard solutions with different pH values. The 226Ra standard solutions were sealed and stand for 38 days in a 250 mL vial specific for the RAD-7. After measured by the WAT250 mode of the RAD-7, the data were measured as (52.5 ± 8.9)%∼(83.6 ± 11.0)% of the prepared concentration of 222Rn (from 226Ra). The emanation rate of 222Rn from standard solution under pH 1.44–9.07 was (53.2 ± 6.9)% ∼(84.3 ± 11.1)% and decreased with pH to a minimum value at 7.00. Moreover, the effect of temperature increases with pH. High correlated trend curves (r2 = 0.9829–0.9999) for 222Rn emanation rate versus pH under different temperature were obtained. A smooth curved surface fitted by the MATLAB for emanation rate of 222Rn was accordingly derived. The 222Rn concentrations in waters of the Beitou Hot Spring (acid-digestion sulfate spring on sedimentary rock strata), Wulai Hot Spring (sodium bicarbonate spring on metamorphic rock strata), Choshuitan (sodium bicarbonate spring on mudstone strata) and Zhaori Hot Spring (acid-digestion sulfate spring on andesite strata) were measured with RAD-7 by WAT250 for 50 min and then calibrated by 222Rn emanation rate estimated above, which were 215 ± 37 (Bq/m3), 6797 ± 1073 (Bq/m3), 2124 ± 577 (Bq/m3) and 26644 ± 2768 (Bq/m3).

Mathematical Modelling to estimate Radon exhalation rates: A study on soil samples from Pangi valley of Chamba district, Himachal Pradesh, India

Radon being radioactive gas is the main source of radiation exposure in the environment. When inhaled, it may cause carcinogenic diseases due to alpha emission during the radon decay, as alpha particles may damage respiratory and alveolar epithelial cells. Thus continuous investigation of the radon level in the environment is always required. In the same, correlation between concentration of radium with radon exhalation rates in the soil samples may be very helpful to know the variation of the radon level. In present study soil samples have been collected randomly from various locations of Pangi Valley of Chamba district, Himachal Pradesh, a northern hill state of India. Radon exhalation rates in collected samples have been measured using the closed can technique in correlation to different soil parameters. Radon mass exhalation rate in soil samples have found to vary from 0.018 to 0.179 Bq kg-1 h-1 with an average value of 0.082 Bq kg-1 h-1 and area exhalation rate from 0.56 to 5.42 Bq m-2 h-1 with an average of 2.47 Bq m-2 h-1. A Mathematical model has been developed using soil parameters viz. bulk density, porosity, emanation rates, diffusion coefficients etc. and use to estimate the radon exhalation rates in soil samples. A strong positive correlation has been obtained between the theoretically estimated and experimentally measured obtained values.

Variable 222Rn emanation rates in an alluvial aquifer: Limits on using 222Rn as a tracer of surface water – Groundwater interactions

Radon-222 (222Rn) is routinely used as a tracer of surface water (SW) – groundwater (GW) interactions. However, methods that rely on this tracer to quantify SW-GW exchange fluxes, GW residence time, SW-GW mixing ratios, or GW flow velocities usually depend on the assumption of spatially constant 222Rn production within aquifers and/or hyporheic sediments. In the present study, we measure the natural variability of 222Rn emanation rates in a highly instrumented alluvial aquifer and underline some important issues in assuming homogenous 222Rn production in alluvial systems. A robust experimental setup was used to determine 222Rn emanation rates from sediments. High-resolution measurements reveal that 222Rn emanation rates are highest within the first few meters below the surface. These results have significant implications for the interpretation of 222Rn activities in GW, notably in the vicinity of infiltration zones, as changes in hydraulic conditions can lead to variations in 222Rn signatures that can only be resolved with proper knowledge of the spatial distribution of 222Rn production rates. In such contexts, the assumption of constant 222Rn production leads to an inadequate understanding of SW infiltration patterns, and biased 222Rn-based estimates of SW-GW exchange.

Status of radon exposure in Bangladeshi locations and dwellings.

Potentially higher cancer risk due to exposure from natural background radiation was indicated for the Bangladeshi population by estimations based on the countrywide study. Several regions with elevated natural background exhibited higher soil radium and thorium contents than the world average. Being the decay products of these radioactive elements, natural radon isotopes could constitute environmental risk factors for internal radiation exposure to the lungs of people living in these areas. Although lung cancer is one of the most prevalent types of cancer in Bangladesh, its status and features are still unclear. To clarify the present status of one of the potential risk factors for lung cancer in the country, this review intends to ascertain the countrywide radon exposure, and its pathways by types of local dwelling and by regions, which would provide an indication of the internal exposures in areas of elevated natural background radiation and radionuclides of soil as well as an understanding of the preliminary contribution of environmental radon on the country's lung cancer prevalence. In this review, countrywide monitored air radon exposures for Bangladeshi dwellings and workplaces are organized from peer-reviewed published papers. Radon has been identified as one of influential sources of radiation dose in Bangladesh with its higher radon exhalation and emanation rate from soil. A novel nationwide depiction of the overall assessed indoor and soil radon levels for Bangladesh has been made through radiation maps. This would be helpful for designing future systematic radon/radiological monitoring and research on the country's lung cancer prevalence.

Emission Patterns of Esters and Their Precursors Throughout Ripening and Senescence in ‘Redchief Delicious’ Apple Fruit and Implications Regarding Biosynthesis and Aroma Perception

The volatile profile of ‘Redchief Delicious’ apple (Malus ×domestica Borkh.) fruit was evaluated at 18 time points from 3 weeks before to 8 weeks after onset of autocatalytic ethylene production to capture the dynamics associated with development from mature green to senescent fruit. Minor amounts of ester production began several days before the onset of ethylene production. Ester production rose rapidly as internal ethylene levels increased beyond 22 nmol·L−1 (0.5 µL·L−1). Peak ester production roughly coincided with maximum ethylene synthesis, declining thereafter. Ester production was further evaluated according to the acid- (alkanoate) and alcohol- (alkyl) derived portions of the ester. The maximum rate of production for a given ester tended to occur later in development as the chain length of the alcohol-derived portion declined. The production rate for many esters paralleled the rate of emanation of their respective alcohol substrates, suggesting that availability of the alcohols limits ester production more than availability of the acid substrates. Combining production rates with sensory descriptors and human sensitivity to individual volatiles permitted approximations of aroma sensations likely engendered by the fruit throughout ripening. Overripe and alcoholic sensations are predicted to increase 2 weeks after the initiation of ripening in response to an increase in the production of ethyl esters. Acetate esters predominated, comprising 50% to 80% of esters throughout maturation and ripening, indicating that the substrate acetyl-CoA may be at saturating levels for alcohol acyl transferase (AAT) at the final step of ester formation. Acetate feeding did not enhance ester production, although label from 13C-acetate was extensively incorporated into esters. The data are consistent with the action of multiple AAT isozymes differing in activity and substrate preference. Incorporation of labeled 13C-acetate into precursors of esters, alcohols, and acids, reflected ester biosynthesis via 1- and 2-carbon chain elongation pathways in ripening ‘Redchief Delicious’ apple fruit.

MODELING AND EXPERIMENTS TO ESTIMATE RADON EMANATION FACTOR IN SOIL-GRAIN SIZE AND MOISTURE EFFECT.

The influence of soil grain size on its radon emanation mechanism was investigated by developing a Monte-Carlo model. The proposed model supplements the previous formulations by accounting for the effect elicited by specific surface area of the sample. The specific surface area of a sample is governed by its grain size and it strongly influences the emanation rate which is a surface phenomenon. The emanation study was further extended to include the moisture effect. Experiments were carried out with two soil samples; Soil-2 and Soil-4 collected from different terrains, to analyze the role played by moisture in the emanation mechanism. The above model was augmented with provisions to include the moisture input. The model could reproduce the experimental results. There is an abrupt increase in the emanation factor when the moisture content changes from 0 to 2%. Thereafter, the increase is gradual and finally becomes steady when the moisture level reaches 10%. Soil-2 and Soil-4 showed sizeable difference in their radon emanation factor values. This could be explained based on the parent226Ra distribution pattern which stems from the mineralogical composition of the samples. Quartz was predominantly found in Soil-2, whereas Soil-4 shows peaks corresponding to minerals namely ilmenite, Rutile and Zircon confirming relatively higher concentration of heavy minerals than Soil-2. The emanation factor values of the individual minerals reported in the literature were used to decide upon the 226Ra distribution depth and with this input the model to ascertain the experimental observations.

Radon and thoron exhalation rate, emanation factor and radioactivity risks of building materials of the Iberian Peninsula.

Radon (222Rn) and thoron (220Rn) are radioactive gases emanating from geological materials. Inhalation of these gases is closely related to an increase in the probability of lung cancer if the levels are high. The majority of studies focus on radon, and the thoron is normally ignored because of its short half-life (55.6 s). However, thoron decay products can also cause a significant increase in dose. In buildings with high radon levels, the main mechanism for entry of radon is pressure-driven flow of soil gas through cracks in the floor. Both radon and thoron can also be released from building materials to the indoor atmosphere. In this work, we study the radon and thoron exhalation and emanation properties of an extended variety of common building materials manufactured in the Iberian Peninsula (Portugal and Spain) but exported and used in all countries of the world. Radon and thoron emission from samples collected in the closed chamber was measured by an active method that uses a continuous radon/thoron monitor. The correlations between exhalation rates of these gases and their parent nuclide exhalation (radium/thorium) concentrations were examined. Finally, indoor radon and thoron and the annual effective dose were calculated from radon/thoron concentrations in the closed chamber. Zircon is the material with the highest concentration values of 226Ra and 232Th and the exhalation and emanation rates. Also in the case of zircon and some granites, the annual effective dose was higher than the annual exposure limit for the general public of 1 mSv y−1, recommended by the European regulations.

THE INFLUENCE OF PINHOLES IN WATERPROOFING MATERIALS ON THE VALUE OF THE RADON DIFFUSION COEFFICIENT.

This article focuses on an experimental study of the influence of imperfections on the value of the radon diffusion coefficient of various waterproofing materials. Microscopic holes were made by a thin tip or by a microdrill bit to imitate the real damage that can be incurred during construction. To determine the change in the radon diffusion coefficient, each waterproofing material was measured five times. The first measurement was performed on undamaged samples, while the following measurements were performed on samples with one, two, four and eight pinholes. The radon diffusion coefficient was measured under nonstationary conditions, because homemade radon sources with a slow rate of radon emanation were used. The radon diffusion coefficients identified in the study were compared according to the thickness of the material and the number and the size of the pinholes. The exact shape and size of the imperfections were documented by an electron microscope.

Building material radon emanation and exhalation rate: Need of a shared measurement protocol from the european database analysis

In this paper the authors present a collection of radon emanation and exhalation rate data of about 2000 samples of building materials used in Europe. The data analysis highlighted some critical issues, such as the use of different units to express radon exhalation rate, the use of different measurement techniques and the general lack of information about density and thickness of samples. In many cases these differences of type and amount of information make difficult a reliable comparison of the obtained data. In the light of these considerations, the need arises to start, at both national and European level, a research activity aimed to develop a shared protocol for measuring the radon exhalation rate based on widely used and reliable measurement techniques. At European level, this protocol could support in forthcoming EU Member States national radon action plans, to take into account the contribution of building materials to the indoor radon concentrations.

Statistical inferences from measured data on concentrations of naturally occurring radon, thoron, and decay products in Kumaun Himalayan belt.

Regional averages of radon, thoron, and associated decay product concentration are reported to be higher than their respective global averages in recent studies conducted in Indian Himalayan belt. The present study explores another region in Indian Himalayan belt by conducting measurements of radon, thoron, and decay product's activity concentration in 92 dwellings of Bageshwar district. The year-long measurements were performed in all 3 seasons distinguishing dwellings as per their construction material. The average radon and thoron concentration for the study region was measured as 57Bq/m3 and 66Bq/m3, respectively. Analysis of the measured data in terms of seasonal effects and construction material led to well established inferences, i.e., higher concentration for mud houses and for winter season. In addition, the present study focuses on lesser probed statistical inferences. One of them is related to the appropriateness of frequency distribution function for the measured data and other dwells upon the correlation analysis of inter-related factors for high concentration cases. Three distribution functions (Lognormal, Weibull, and Gamma) were found to be following the trend of frequency distribution curve of the measured data. For mud houses in winter season, variations of radon/thoron concentration were attempted to correlate with mass/surface exhalation rate, emanation rate, and source term content. More than 80% of the dwellings of the study region were found to have gas and decay product's concentration levels, higher than the respective global average values. However, these values were mostly within the reference levels for residential environments. Nevertheless, this region requires further studies to pinpoint the causes for elevated levels and suggest simple remedial modifications if required.

Agricultural soils a trigger to nitrous oxide: a persuasive greenhouse gas and its management.

Agricultural soils form the backbone of the country's economic development. The increased population has not only reduced this treasure but also has affected the global climate at an alarming rate. Among the GHGs, emission of N2O due to agricultural activities is nowadays a global concern. Agricultural industries have increased N2O and CH4 by 17% in the atmosphere since 1990, with an average emanation rate of around 60 MT CO2 equivalents per year. Crop production accounts for approximately 50% of N2O emissions stemming from the farming community and discharges of fertilizer-induced N2O, for the time being estimated by IPCC at 1.24% of the N used ranging from 0.76% (rice) to 2.77% (maize). The concentration of atmospheric N2O has increased (60ppb) after the industrial revolution, at the pace of 0.73ppbyear-1. Besides, soil structure, temperature, moisture, denitrifying microbial population, pH, C:N ratio, and relief are the factors which significantly enhance the N2O levels into the atmosphere. N2O as a GHG has more potential towards global warming than CO2 and has a very long residence period (115years) in the atmosphere. N2O emission is nowadays a core issue which needs to be mitigated so as to decline the levels of its production in agricultural soils. However, priority should be given to the organic farming, management of soil chemistry, and phytoremediation to reduce the addition of N2O into the ambient air. Furthermore, deployment of N2O reductase in agricultural soils increases the efficiency of converting N2O to inert N2 which is a valuable strategy to reduce N2O production.

Investigation of 220Rn emanation and exhalation from soil samples of Larsemann Hills region, Antarctica

In the present study, thoron exhalation flux density were measured in the soil samples collected around the Indian station namely Bharati (69° 24.41′ S, 76° 11.72′ E) and its nearby islands in the Larsemann hills region of Antarctica. Further, dependency of thoron mass emanation rate and emanation coefficient on the soil grain size was studied by segregating the soil samples into four different grain size groups: 50–100 μm, 100–200 μm, 200–500 μm and 500–1000 μm which showed that both of them follow a decreasing trend with increase in grain size. A comparison of measured mass emanation rate between different soil samples showed that it had a larger variation for the smaller grain size which eventually decreased as grain size increased while emanation coefficient was observed to be nearly constant for all the grain size groups. The variation in emanation coefficient with respect to mean grain size has been investigated and an empirical exponential model has been proposed for predicting emanation coefficient for different grain sizes.