Radon Data Research Articles

Radon data processing and outputs for the needs of the State Office for Nuclear Safety (according to the Czech Radon Programme)

Much of the population living in the Czech Republic is exposed to radiation from natural sources, especially to the radon effect. The aim of geological research defined by the State Office for Nuclear Safety (SONS) was to detect areas with estimated high radon concentration in soil gas. A uniform method of measurements and uniform methodology of radon risk category assessment of geological units and a centralized radon database was established. Radon risk classification was based on statistical evaluation of soil gas radon concentration and permeability in investigated geological units. Prognostic radon risk maps in various scales were the main outputs of this research. With the help of GIS tools spatial analyses were found a correlation between soil gas radon values in selected geological units and indoor measurements in dwellings. After verification of the efficiency of track etch detectors placed in dwellings with the help of prognostic maps 75% reliability of these maps was proven. This reliability of analyses induced the SONS to widely use radon risk maps to determine areas with predicted high radon risk category.

Spatial distribution of indoor radon in Triveneto (Northern Italy): a geostatistical approach

The study of spatial distribution of the indoor radon has assumed in the last years a lot of interest. The geostatistical techniques turn out to be particularly promising. The present work presents the results of a study where around 4000 indoor radon data from Veneto, Friuli Venezia-Giulia and Alto Adige, collected during the sampling campaigns performed in dwellings and in schools, have been analyzed. After the definition of the common data set, the study of the spatial distribution of the phenomenon has been performed by examining the experimental variograms. Declustering techniques have been applied. Predictive maps were defined by using simulation techniques; they allow to determine the probabilities of exceeding defined concentration levels, the 'radon-prone' areas. Systematic results regarding the validation of these maps are reported. This methodological study indicates how it is possible to understand the geographical variability of the phenomenon, trying to find out correlations among indoor radon, geological characteristics (i.e. lithology, morphology, tectonics, soil gas) and building-specific features, which can significantly influence radon concentrations.

Radon transform inversion using the shearlet representation

The inversion of the Radon transform is a classical ill-posed inverse problem where some method of regularization must be applied in order to accurately recover the objects of interest from the observable data. A well-known consequence of the traditional regularization methods is that some important features to be recovered are lost, as evident in imaging applications where the regularized reconstructions are blurred versions of the original. In this paper, we show that the affine-like system of functions known as the shearlet system can be applied to obtain a highly effective reconstruction algorithm which provides near-optimal rate of convergence in estimating a large class of images from noisy Radon data. This is achieved by introducing a shearlet-based decomposition of the Radon operator and applying a thresholding scheme on the noisy shearlet transform coefficients. For a given noise level ε, the proposed shearlet shrinkage method can be tuned so that the estimator will attain the essentially optimal mean square error O ( log ( ε − 1 ) ε 4 / 5 ) , as ε → 0 . Several numerical demonstrations show that its performance improves upon similar competitive strategies based on wavelets and curvelets.

Precursory signatures in the radon and geohydrological borehole data for M4.9 Kharsali earthquake of Garhwal Himalaya

Continuous recording of different geophysical parameters incorporated at a single location as a unified effort for earthquake precursory through geodynamical changes initiated for the first time in the Garhwal Himalaya, India. A 68 m deep borehole, penetrating into the water table is operated for continuous radon monitoring along with meteorological/geohydrological observations at two points, one at 10 m (in the air column) and the second one at 50 m (within water column) depths from surface. Preliminary studies reveal diagnostic short duration anomalies in radon concentration recorded few days before the occurrence of a nearby moderate M4.9 earthquake at Kharsali on the 23rd of July, 2007. For nearly half of the year, radon emanation at 10 m depth in the closed air column showed definite pattern of daily variations that may be due to the influence of tidal forces, meteorological and other geodynamical phenomena. This pattern is totally missing during June and July, 2007 when few anomalies for small durations were observed out of which two are unique. These two anomalies exceed 2 σ (standard deviation) from average radon concentration in both positive and negative sides. However, its emanation at 50 m depth (water radon) is almost constant throughout the year 2007 except some disturbances observed to the ending of June and during July. These abnormalities in radon emanation and other parameters in the borehole may be considered precursory to the M4.9 Kharsali earthquake of July 23, 2007 having an epicenter distance of 60 km. The empirical relation used for amount of radon anomaly with the epicenter distance predicts an earthquake of M4.6 and M4.7 with the observed anomaly at 10 m and 50 m observation points respectively after taking a 60 km epicenter distance.

Statistical analysis of indoor radon data for the Walloon region (Belgium)

Two databases of indoor radon measurements in the Walloon region in Belgium can be used to establish a radon risk map of this region, taking into account the geological information. The data were collected, respectively, by long-term track-etch measurements and by short-term charcoal measurements. Here we present a preliminary study showing that the two databases can be merged. We begin our study by testing two types of distributions: the log-normal distribution and the log-Gumbel distribution, with the purpose of selecting the best to fit our databases. The paper then describes a methodology that allows us to combine them. The composite database will be used to establish a radon risk map for the Walloon region based on geology.

A STUDY OF RESIDENTIAL RADON IN SWEDEN USING MULTI-LEVEL ANALYSIS

A Swedish radon data set, consisting of more than 8,000 measurements of residential radon levels in about 50% of the Swedish municipalities, was analyzed using a multi-level approach. The results were compared with those of a single-level analysis. We found that there was a significant variability between municipalities. The point estimates of the population mean radon levels were similar (geometric mean 60 Bq m-3 and arithmetic mean 106 Bq m-3). The analysis shows the advantages of multi-level modeling compared with a single-level ordinary least squares (OLS) model. A single-level model results in too optimistic standard errors, about 25% of those of the multi-level model, which can lead to erroneous conclusions. In a multi-level model including house type as a fixed effect (single-family house, row house, or apartment in multi-family house), the estimates of the fixed effect of house type were similar for the single-level and the multi-level models.

A preliminary design of a radon potential map for Canada: a multi-tier approach

Canada is a vast country with most of the population living on a small portion of the land. However, for a national radon potential map, it is mandatory to cover the entire country including sparsely populated areas. Because of these characteristics, the radon map development for Canada is challenging. After briefly reviewing of radon map development in the world, this study considers a multi-tier approach to best use available however limited resources and to generate a national radon map in a timely fashion. In summary, radon potential maps for highly populated areas should be determined by direct indoor radon measurements where enough indoor radon data are available. In areas where indoor radon measurements are limited or not yet available, the radon potential maps could be developed from various data sources with a multi-factor scoring system including geological information on soil permeability, soil gas radon concentration and ground uranium concentration. In sparsely populated areas, radon potential maps can only be generated with geological predictive tools, especially in those areas where no houses have yet been built. Because indoor radon measurement data and geological information relevant to radon are very limited in Canada, a multi-step strategy is also worth considering in addition to the multi-tier approach.

Uncertainty of block estimates introduced by mis-allocation of point samples: on the example of spatial indoor Radon data

The European indoor Radon map which is currently under production is based on gridded data supplied by the contributing countries. Each grid node represents the arithmetic mean (among other statistics) of the individual measurements within 10 × 10 km 2, called cells, pixels or blocks, which are aligned to a common metric coordinate system. During work the question emerged, if uncertainty in the geo-referencing of individual data might affect the aggregated “block” statistics to an extent that the statistics have an unpredictably high additional uncertainty, which makes them unusable. In this note we try to quantify the effect, based on simulations. The overall result is that the relevant statistics should not be affected too badly in most cases, in particular if the rate of mis-allocations, and the mean uncertainty of coordinates are not too high, so that also cell statistics which are to some degree distorted by mis-allocated data, can still be used for the purpose of the European Radon map.

Re-analysis of the experiment data of vertical migration of radon and its daughters under ideal condition

Helium-radon clusters will migrate upwards provided the clusters are made up of one radon atom and more than 8 helium atoms. With less than 8 the atoms, the specific gravity of the helium-radon clusters will be heavier than their buoyancy and the clusters will migrate downwards. Hence the average number of atoms will be greater 1a upwards-migrating clusters. The mathematical calculation has been done to obtain the average atomicity of clusters from experimental radon data. The results show that the number of α particles provided by uranium ore is insufficient, if not considering the diffusion of radon, because one radon atom needs to combine with 7.5 helium atoms. But if the diffusion of radon is taken into account, there will have enough number of α particles because one radon atom needs to combine with just 4.26—5.57 helium atoms. Therefore, the diffusion of radon cannot be ignored when we apply the migration mechanism of helium-radon clusters to explain the vertical migration experiment data of radon and its daughters.

Underground sources of nutrient contamination to surface waters in Bangkok, Thailand

Radon-222 is very concentrated in groundwater relative to surface waters and thus serves as an effective groundwater discharge tracer. We observed spikes in radon data from an earlier (2004) survey of the Chao Phraya River that appeared to correspond to locations where major canals (“klongs”) enter the river. We returned in 2006 and conducted more detailed surveys along some of the main klongs on the western (Thonburi) side of the Chao Phraya to evaluate this possibility. Our results show that both radon and conductivity are enriched in some areas of the klongs with 3 apparent “end-members,” two of which are likely related to groundwater seepage. Furthermore, nutrient analyses conducted during a time-series experiment at a site of suspected high discharge (Wat Intharam, Klong Bangkok Yai) showed that dissolved inorganic nitrogen (DIN) and phosphate correlated significantly to the groundwater tracer, radon. Rough estimates of the nutrient fluxes in this area are orders of magnitude higher than those measured in coastal settings and may represent a significant fraction of the riverine flux. It thus appears very likely that seepage of shallow groundwater is an important pathway for nutrient contamination of the klongs, and thus to the river, and ultimately to the Gulf of Thailand.

Seasonal variability of radon-derived fetch regions for Sado Island, Japan, based on 3 years of observations: 2002–2004

Three years of hourly atmospheric radon measurements at Sado Island (Japan) are discussed and compared with corresponding measurements at Gosan (South Korea), and Hok Tsui (China). In conjunction with back trajectory analysis, Sado radon data are used to characterise the seasonal variability in fetch regions of air masses subject to extremes of terrestrial influence. In winter, fetch regions of air masses that have experienced the greatest terrestrial influence covered southern Siberia; in summer, the terrestrial fetch was dominated by Japan; throughout the remaining months the terrestrial fetch encompassed the Korean Peninsula and far eastern China. Summer radon data are then used to estimate the radon flux from central Honshu (23.5 mBq m −2 s −1), which varied regionally between 10.6 and 47.9 mBq m −2 s −1. The Sado radon record reported here completes a 4-site, multi-year dataset of hourly radon concentrations across East Asia and the central Pacific (spanning 16° of latitude), which constitutes a unique evaluation tool for transport and mixing schemes of atmospheric and chemical transport models.

POPULATION ATTRIBUTABLE FRACTION FOR LUNG CANCER DUE TO RESIDENTIAL RADON IN SWITZERLAND AND GERMANY

Studies on miners as well as epidemiological studies in the general population show an increased lung cancer risk after exposure to radon and its progeny. The European pooled analysis of indoor radon studies estimates an excess relative risk of 8% (16% after correction for measurement uncertainties) per 100 Bq m(-3) indoor radon concentration. Here, we determine the population attributable fraction (PAF) for lung cancer due to residential radon based on this risk estimate for Switzerland and Germany. Based on regionally stratified radon data, the PAF was calculated following the World Health Organization concept of global burden of disease, compared to a realistic baseline radon concentration equal to the outdoor concentration. Lifetable approaches were used taking smoking and sex into account. Measurement error corrections were applied to both risk estimates and the radon distribution. In Switzerland, the average indoor radon concentration is 78 Bq m(-3), resulting in a PAF of 8.3%. Therefore, 169 male lung cancer deaths and 62 deaths in women can be attributed to residential radon per year. For Germany, the average indoor radon concentration is 49 Bq m(-3), corresponding to a PAF of 5.0% (1,422 male and 474 female deaths annually). In both countries, a large regional variation in the PAF was observed due to regional differences in radon concentrations and population structure. Both calculations show a strong dependency on the risk model used. Risk models based on miner studies result in higher PAF estimates than risk models based on indoor radon studies due to different assumptions regarding exposures received more than 35 years ago. The use of a non-zero baseline radon concentration also contributes to the lower PAF estimates reported here. Although the estimates of the population attributable fraction of residential radon presented here are lower than previously reported estimates, the risk is still one of the most widespread environmental hazards. Radon monitoring and radon reduction programs are therefore important issues for environmental public health management.

Differentiation between earthquake radon anomalies and those arising from nuclear activities

The present work offers a methodology to correlate the earthquake time, magnitude and location based on the behavior of radon concentration. By correlating tectonic events to radon behavior, based on previously published radon data, radon concentration signals can be taken into consideration in decision making. Three correlations between magnitude, time and epicenter distance are presented. The applicability of any one of them depends on the measurement technique. Moreover, a suggested procedure is presented to determine the possible confusion between signals for radon anomalies originating from tectonic failure and those arising from nuclear activities. The suggested method depends on the change observed on the 219Rn and 222Rn daughters concentration ratios.

Pilot study of the application of Tellus airborne radiometric and soil geochemical data for radon mapping

The scope for using Tellus Project airborne gamma-ray spectrometer and soil geochemical data to predict the probability of houses in Northern Ireland having high indoor radon concentrations is evaluated, in a pilot study in the southeast of the province, by comparing these data statistically with in-house radon measurements. There is generally good agreement between radon maps modelled from the airborne radiometric and soil geochemical data using multivariate linear regression analysis and conventional radon maps which depend solely on geological and indoor radon data. The radon maps based on the Tellus Project data identify some additional areas where the radon risk appears to be relatively high compared with the conventional radon maps. One of the ways of validating radon maps modelled on the Tellus Project data will be to carry out additional indoor measurements in these areas.

Variation of soil radon concentrations in southern Ontario

Radon has been identified as the second leading cause of lung cancer after tobacco smoking. Information on indoor radon concentrations is required to assess the lung cancer burden due to radon exposure. However, radon data in highly populated southern Ontario are very limited. Since radon in soil is believed to be the main source of radon in homes, measurements of soil gas radon concentrations can be used to estimate variations in radon potential of indoor environments. This study reports a transect survey of natural background variation in soil radon levels across southern Ontario. The results indicate that radon risk could be high in some areas of southern Ontario.

Comparison of various methods of estimating radon dose at underground workplaces in wineries

Levels of radon were surveyed in the air at underground workplaces of eight major Slovenian wineries. Geometric mean and geometric standard deviation values, respectively, obtained with different devices were 81 Bq m(-3) and 2.3 with alpha scintillation cells, 114 Bq m(-3) and 2.0 by exposing etched track detectors for 1-5 months, and 183 Bq m(-3) and 2.6 from 1-4-weeks continuous measurements. The equilibrium factor was 0.25-0.67, and the unattached fraction of radon short-lived decay products was in the range 0.09-0.20. Effective doses were calculated and compared based on radon data obtained with different techniques.

Prediction of indoor radon in Germany on a regional scale

Abstract Measurements of indoor radon activity concentration have been carried out in more than 10 000 dwellings in different regions of Germany. The statistical correlations between geology, building ground, indoor radon and the house characteristics were investigated. The geographical location – and therefore the geological setting – can be used as a proxy for both region-specific geological properties and building characteristics. Together with different variables of house type and living habits it significantly contribute to the explained variance for both ground floor and basement radon activity concentrations. Soil gas and indoor radon activity concentrations are connected by a transfer factor. The study has shown, that this factor can vary depending on regional differences in building characteristics, especially between the western and eastern part of Germany. Radon risk prediction maps for radon in houses based on the German soil gas map and the regional distribution of radon transfer, indicating the probability of exceeding indoor threshold values, can be designed. They can be used as a tool for indoor radon prediction, especially in regions without a sufficient number of indoor radon data.

γ-Ray spectrometry of radon in water and the role of radon to representatively sample aquifers

Measurement of radon in water by γ-ray spectrometry using a HPGe detector has been investigated to determine aquifer characteristics. The radon activity concentration is determined by taking the weighted average of the concentrations derived from γ-ray lines associated with 214Pb and 214Bi decay. The role of accurate radon data to representatively sample aquifers was also investigated by studying a semi-cased borehole. A simplified physical model describing the change of radon concentration with the pumping time, reproduces the data and predicts the time for representative sampling of the aquifer.

Soil gas radon, indoor radon and gamma dose rate in CZ: contribution to geostatistical methods for European atlas of natural radiations

A comparison of Czech indoor radon data, soil gas radon data and gamma dose rate was performed on the data sets of 92,276 indoor radon measurements in existing dwellings (National Radiation Protection Institute - NRPI), database of 9500 test sites of soil gas radon measurements (Czech Geological Survey - CGS) georeferenced to levels of gamma dose rate map. Three methods were used for the study of soil gas Rn-indoor Rn relationship: (1) based on the vectorised point soil gas and indoor data related to vectorised areas of gammadose rate, (2) vectorised soil gas-indoor data based on vectorised geological units and (3) soil gas and indoor data related to grid squares 10 x 10 km2. The first and second methods seem to express the closer correlation compared with the third one, however the correlation using the third method is influenced by the representativeness of data value in the square of 100 km2 area. On the other hand, the third method can be used for the overview coverage of the continental areas with lack of input information.

Radon in soil gas--investigation and data standardisation at radon reference sites, Czech Republic

Radon risk mapping at building sites in the Czech Republic indicate an advisable level of protection of buildings against the penetration of radon from the geological basement. Various techniques and instruments are used for the measurement of radon in soil gas. A national radon chamber and three radon reference sites in Central Bohemia enable radon data standardisation. Tests of field radon measurements and the reported radon activity concentration in soil gas at the reference sites are based on comparisons with other organisations and with a database of reference site measurements. The radon reference sites have been used for various investigations of radon in soil gas during the period 2000-07.