Relationship between radon concentrations in indoor air and in soil gas

In the Ljubljana region, 53 schools were selected for measurements of radon concentrations in soil gas close to a school building, and indoor radon concentrations in one of the ground-floor classrooms of each building. The aim was to establish a relationship between radon concentrations in indoor air and in soil gas from the ground on which the building is situated. Soil gas radon concentrations between 2 and 14 kBqm^-3 were found. Indoor radon concentrations ranged from 20 to 1,440 Bqm^-3, with seven values exceeding 200 Bqm^-3. It is concluded that good quality of the construction elements ensure low indoor radon concentration, regardless of high soil gas radon level.     

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.     

Predicting New Hampshire indoor radon concentrations from geologic information and other covariates

 Generalized geologic province information and data on house construction were used to predict indoor radon concentrations in New Hampshire (NH). A mixed-effects regression model was used to predict the geometric mean (GM) short-term radon concentrations in 259 NH towns. Bayesian methods were used to avoid over-fitting and to minimize the effects of small sample variation within towns. Data from a random survey of short-term radon measurements, individual residence building characteristics, along with geologic unit information, and average surface radium concentration by town, were variables used in the model. Predicted town GM short-term indoor radon concentrations for detached houses with usable basements range from 34 Bq/m³ (1 pCi/l) to 558 Bq/m³ (15 pCi/l), with uncertainties of about 30%. A geologic province consisting of glacial deposits and marine sediments was associated with significantly elevated radon levels, after adjustment for radium concentration and building type. Validation and interpretation of results are discussed. Received: 20 October 1997 · Accepted: 18 May 1998     

Increased soil gas radon and indoor radon concentrations in Neoproterozoic olistostromes of the Teplá-Barrandian unit (Czech Republic)

The Neoproterozoic olistostromes were first distinguished as a special geological unit in a generalised geological map of the Czech Republic on a scale 1:500,000. The olistostromes represent a tectonic mélange or subaquatic continental slope-slides formed by a mixture of black shales, greywackes, carbonates and shales, forming an extremely inhomogeneous geological environment. The extreme over-limit values of indoor radon (Rn, ²²²Rn) were first detected during check measurements performed for final building approval by team of the National Radiation Protection Institute in a house situated on bedrock of black shales—lithological component of olistostromes north-eastward from Plzeň. Additional measurements of soil gas Rn performed by the Czech Geological Survey were oriented to cover the whole olistostrome belt extending over 65 × 25 km area NE of Plzeň–Prague general direction. The increased concentrations both of soil gas and indoor Rn were confirmed in the whole extent of Neoproterozoic olistostrome belt compared to neighbouring geological units (Neoproterozoic metasediments on NW and Cambrian Palaeovolcanites and Ordovician sediments on SE). This observation lead to increasing the radon index of olistostromes to medium radon category (from the low one) both in general and detailed Rn index maps. Drawing the attention to this lithological type enables to improve the radon risk prevention for newly built houses and interest of remediation of existing houses not only in the specific area of the Czech Republic, but also in other European countries, where Neoproterozoic olistostromes form the geological basement.     

Mapping radon-prone areas - a geophysical approach

 Radon-prone areas in Israel were mapped on the basis of direct measurements of radon (²²²Rn) in the soil/rock gas of all exposed geological units, supported by the accumulated knowledge of local stratigraphy and sub-surface geology. Measurements were carried out by a modified alpha-track detection system, resulting in high radon levels mainly in rocks of the Senonian-Paleocene-aged Mount Scopus Group, comprised of chert-bearing marly chalks, rich in phosphorite which acts as the major uranium source. Issues of source depth, seasonal variations and comparison with indoor radon levels are addressed as well. This approach could be applied to other similar terrains, especially the Mediterranean Phosphate Belt.     

Geological and geochemical factors affecting radon concentrations in dwellings located on permeable glacial sediments—a case study from Kinsarvik,Norway

In 1996–1997, indoor radon values of more than 40,000 Bq/m³ and large seasonal and geographical variations in indoor air radon were reported from a residential area located on a highly permeable ice-marginal deposit. Geochemical analyses of bedrock, groundwater and sediments and comparisons between indoor radon values and soil radon values indicate that the indoor radon concentrations in this area are strongly affected by subterranean airflows caused by temperature differences between soil air and atmospheric air. The airflows concentrate the radon-laden soil air towards the topographic highest part of the deposit in winter and towards the topographic lowest part in summer. In areas where subterranean airflows are likely to occur, radon measurements performed both in summer and in winter provide the best estimate of annual average indoor radon concentrations, and assessments of indoor radon concentrations based on single soil gas measurements are not recommended.     

A geostatistical approach for mapping and uncertainty assessment of geogenic radon gas in soil in an area of southern Italy

Spatial distribution of concentrations of radon gas in the soil is important for defining high risk areas because geogenic radon is the major potential source of indoor radon concentrations regardless of the construction features of buildings. An area of southern Italy (Catanzaro-Lamezia plain) was surveyed to study the relationship between radon gas concentrations in the soil, geology and structural patterns. Moreover, the uncertainty associated with the mapping of geogenic radon in soil gas was assessed. Multi-Gaussian kriging was used to map the geogenic soil gas radon concentration, while conditional sequential Gaussian simulation was used to yield a series of stochastic images representing equally probable spatial distributions of soil radon across the study area. The stochastic images generated by the sequential Gaussian simulation were used to assess the uncertainty associated with the mapping of geogenic radon in the soil and they were combined to calculate the probability of exceeding a specified critical threshold that might cause concern for human health. The study showed that emanation of radon gas radon was also dependent on geological structure and lithology. The results have provided insight into the influence of basement geochemistry on the spatial distribution of radon levels at the soil/atmosphere interface and suggested that knowledge of the geology of the area may be helpful in understanding the distribution pattern of radon near the earth’s surface.     

A comparison of field and laboratory analytical methods for radon site investigation

Soil-gas radon measurements provide a valuable tool in assessing probable indoor radon levels on a regional basis. However, in Great Britain, seasonal weather changes can cause large changes in soil-gas radon concentration. Although this does not significantly constrain systematic radon potential mapping programmes, it does cause difficulties in responding to ad-hoc requests for site-specific radon investigations. The relationship between soil-gas radon and gamma spectrometry measurements made in the field with radon released from a representative sample of soil in the laboratory has been investigated as part of a program to develop a method of radon potential mapping and site investigation which can be used at any time of the year. Multiple soil and soil-gas samples were collected from sites underlain by bedrocks with widely varying radon potentials. For each geological unit, sites both free of and covered by glacial drift deposits were sampled. Soil and soil-gas samples were taken at the same depth of 60–100 cm. The effectiveness of these radon site investigation procedures has been evaluated by studying the relationship between the soil-gas radon, gamma spectrometry and radon emanation data with an independent estimate of the radon risk. The geologic radon potential (GEORP), which is the proportion of existing dwellings which exceed the UK radon Action Level (200 Bq m⁻³) for a particular combination of solid and drift geology within a defined geographic area, has been used for this study as the independent estimate of radon risk. Soil-gas radon, radon emanation and eU (equivalent uranium by field γ spectrometry) are all good geochemical indicators of radon risk (GEORP) in Derbyshire but only soil-gas radon correlates significantly with GEORP in Northamptonshire. Radon in soil gas discriminates more effectively between sites with different radon potential in Northamptonshire if soil permeability is also taken into account. In general, measurement of soil-gas radon in the field provides the most universally applicable indicator of radon potential. If soil-gas radon concentrations cannot be determined because of climatic factors, for example when the soil profile is waterlogged, measurement of radon emanation in the laboratory or measurement of eU can be used as radon potential indicators in some geological environments. This applies particularly in areas where the soil composition rather than the composition and permeability of the underlying rock or superficial deposits are the dominant controls of radon potential. It appears, therefore, that it may be necessary to use different radon site investigation methods according to the specific factors controlling radon emanation from the ground. In some cases no method will provide a reliable indicator of radon risk under unfavourable climatic conditions.     

氡地质潜势规律研究方法探讨

氡的地质潜势是环境氡研究的重要内容,也是从地质背景出发快速评价氡浓度水平的有效方法,氡析出率是反映氡地质潜势的最好参数,根据放射性元素分布规律,地质背景及放射性元素衰变等,建立了计算氡析出率的理论公式。理论计算结果表明,北京市区氡的地质潜势分为四个不同的区,不同潜势区中室内氡浓度水平发生相应变化。说明通过氡地质潜势规律研究,可以确定室内氡浓度水平潜在高值区。     

Distribution of indoor radon concentrations and uranium-bearing rocks in Texas

 The purpose of this study was to compare regional patterns of indoor radon concentration with uranium-bearing rock zones and county populations in Texas. Zones yielding radon concentrations that are relatively high for Texas include shale and sandstone in northwest Texas; red beds in north-central Texas; felsic volcanic rocks in west Texas; and sandstone, limestone, and igneous rocks in central Texas. Located in northwest Texas, only five of the 202 counties evaluated have mean indoor radon concentrations above 4.0 pCi l^–1. Two of those counties have populations above the state median of 20 115. The highest county mean concentration is 8.8 pCi l^–1. Results of this study suggest that (1) regional geology influences indoor radon concentrations in Texas, (2) statewide, the radon concentrations are relatively low, (3) highly populated counties do not coincide with regions of high indoor radon concentration, and (4) regions that may warrant further monitoring include northwest Texas and, to a lesser degree, west and central Texas. Received: 8 August 1995 · Accepted: 6 September 1995     

Radon variations in an active landslide zone along the Pindar River, in Chamoli District, Garhwal Lesser Himalaya, India

Radon measurements were made in the soil and spring/seepage water in and around an active landslide located along the Pindar river in the Chamoli District of Uttaranchal in Garhwal Lesser Himalaya, to understand the application of radon in geological disasters. The landslide is a compound slide i.e. a slump in the crown portion, and debris slide and fall in the lower part. The bedrock consists of gneisses and schists of the Saryu Formation of the Almora Group of Precambrian age. The presence of several small slump scars and debris slide/fall scars along the length of the slide indicates continuous downward movement. The radon concentrations in the present study are much lower in comparison to values reported from other regions. However, the present radon data show relative variation in the slide zone. The concentration of radon measured in landslide zones varies from 3.1 Bq/l to 18.4 Bq/l in spring water and from 2.3 kBq/m³ to 12.2 kBq/m³ in the soil gas of the debris. Along the section of the slide, the radon values in water and soil are slightly higher in the upper slopes i.e. toward the crown portion of the landslide as compared to the distal portion. The relatively low concentration of radon both in soil gas and water in the toe portion of the landslide may be due to the high porosity of the debris, which does not allow radon to accumulate in the soil and water, whereas, towards the crown portion, the high frequency of fractures increases the surface area due to particle size reduction, and the near absence of debris enhances the radon emanation in soil.     

Study of soil gas radon variations in the tectonically active Dharamshala and Chamba regions,Himachal Pradesh,India

Soil gas radon measurements were made in Chamba and Dharamshala regions of Himachal Pradesh, India, to study the correlation, if any, between the soil gas radon, radium activity concentration of soil, and the geology/active tectonics of the study region. Soil gas radon surveys were conducted around the local fault zones to check their tectonic activities using the soil gas technique. Soil gas radon activity concentration at thirty-five different locations in Dharamshala region has been found to be varying from 13.2 ± 1.5 to 110.8 ± 5.0 kBq m^?3 with a geometrical mean of 35.9 kBq m^?3 and geometrical standard deviation of 1.8. Radon activity concentration observed in the thirty-seven soil gas samples collected from the Chamba region of Himachal Pradesh varies from 5.2 ± 1.0 to 35.6 ± 2.5 kBq m^?3, with geometrical mean of 15.8 kBq m^?3 and geometrical standard deviation of 1.6. Average radium activity concentrations in thirty-four soil samples collected from different geological formations of Dharamshala region and Chamba region are found to be 40.4 ± 17 and 38.6 ± 1.7 Bq kg^?1, respectively. It has been observed that soil gas radon activity concentration has a wide range of variation in both Dharamshala and Chamba regions, while radium activity concentrations in soil samples are more or less same in both the regions. Moreover, soil gas radon activity concentration has a better positive correlation with the radium activity concentration in soil samples collected from Chamba region as compared to Dharamshala region.     

土壤氡测量国际比对及几个重要问题

为了保证我国氡填图方法研究中关键参数土壤氡浓度测量结果的准确性和可靠性,笔者所在的实验室作为首次参加氡国际比对的中国组织,参加了2010年在捷克举行的3个氡参考点Cetyně、Bohostice和Buk现场测量国际比对。经T-学生分布检验,当显著性水平α=1%时,本实验室在氡参考点上45个测点的实测土壤氡浓度值cA与全部比对测量参加者的CA(2000年以来该参考点全部组织的平均值)数据有很好的一致性;3个参考点的平均氡浓度与自2000年以来在这些氡参考点进行试验的所有成功组织(N=180)提交数据形成的数据库中的数据高度一致,总相对误差小于6%。该成果表明本实验室的土壤氡测量技术已达国际相应水平。通过本次氡国际比对,发现了我国土壤氡测量中仪器校准、土壤气体采样技术等方面存在的问题,建议系统开展土壤氡测量方法及其技术规范等研究。     

Assessment of soil radon potential in Hong Kong, China, using a 10-point evaluation system

Radon and its progenies have been ranked second of being responsible for lung cancer in humans. Hong Kong has four major groups of uranium-rich plutonic and volcanic rocks and is suffering from radon emanated therefrom. However, there is a lack of radon potential maps in Hong Kong to resolve the spatial distribution of radon-prone areas. A ten-point radon potential system was developed in Germany (2005) to predict radon potential using both the in situ geogenic and geographic parameters under hierarchical ranking. Primarily, the ten-point system requires the desk study of the geological environment of sampling sites, which has an advantage of saving resources and manpower in extensive radon potential mapping over the traditional soil radon concentration sampling method. This paper presents a trial of radon potential mapping in Hong Kong to further verify the system. Despite some slight departures, the system demonstrates an acceptable correlation with soil radon concentrations (R ² = 0.62–0.66) from 768 samples of mainly intermediate radon potential. Hong Kong has a mean soil radon concentrations of 58.9 kBqm^?3, while the radon potential from the ten-point system achieves an average of 4.93 out of 10 over the territory. The vicinity of fault zone showed high soil radon concentrations and potentials, which were conducive to uranium enrichment and rapid soil-gas diffusion near faults. High uranium-238 content in soil was found to cause high soil radon concentration with a large R ², 0.84. The Jurassic granite and volcanic crystal tuff cover more than 85 % of the whole Hong Kong area, and they show relatively high radon concentrations (Geometric mean 83 and 49 kBqm^?3, respectively) which are associated with their high uranium contents (Geometric mean 234 and 197 Bqkg^?1, respectively). While indoor radon concentration is an important factor for radon risk assessment, this study has not considered the correlation between indoor radon concentration and radon potential. The reason is that almost all buildings in Hong Kong are high-rise buildings where indoor radon concentrations are governed only by the radium content in the building materials and the ventilation conditions.     

Impact of the deeper geological basement on soil gas and indoor radon concentrations in areas of Quaternary fluvial sediments (Bohemian Massif,Czech Republic)

The relationship of soil gas radon Rn²²² and indoor radon was studied within the Quaternary fluvial sediments of the Czech Republic. The processing of data selection from the radon database of the Czech Geological Survey and indoor radon data (database of the National Radiation Protection institute) has proved the concentration dependence of radon in Quaternary fluvial sediments on deeper bedrock. The ArcGIS processing was accompanied by the field verification in five profiles, intersecting the granitoid Central Bohemian Plutonic Complex and its rim rock types. Both theoretical and experimental results show dependence of soil gas radon and indoor radon concentrations in Quaternary fluvial sediments on deeper geological basement, thus leading to the conclusion that the lateral transport of Quaternary sediments does not play such a dominant role in radon concentrations, as was thought previously. This fact will enable to determine precisely the radon index of Quaternary sediments (in the Czech radon mapping classified as an intermediate index) into three categories according to the lithology of their geological basement.     

Some measurements of radon in south west England

Summary A survey of radon in soil gas emissions was carried out in the Carnmenellis area of Cornwall to establish the location and extent of any major radon gas concentrations. Measurements of soil radon gas levels showed considerable variation. Radon emission variation with respect to atmospheric pressure was monitored but results showed no correlation between the variables. A survey of schools in the region with high indoor radon concentrations was carried out for comparison with the results of the main survey. A good correlation was found between the two surveys, suggesting that broad-based radon hazard mapping on a local scale may be feasible.     

Radon distributions in the Hail Region of Northern Saudi Arabia

Indoor radon measurements were carried out in a total of 420 dwellings and 17 schools in Hail region of Saudi Arabia, using NTDs based radon dosimeters. The duration of the measurements was one year, from April 2008 to April 2009. The indoor radon concentrations varied from 4 to 513 Bq/m³ with an overall average of 45 Bq/m³ for all surveyed dwellings. These passive measurements were confirmed by the active measurements. The anomalous concentrations above 200 Bq/m³ were observed in 13 dwellings, representing 3.1 % of the total surveyed dwellings. In Inbowan village alone, it was found that 7.6 % of the dwellings have indoor radon concentration above 200 Bq/m³. The highest average indoor radon concentration of 64 Bq/m³ was found in Inbowan village while the lowest average of 24 Bq/m³ was found in Majasah village. The city of Hail showed an average indoor radon concentration of 49 Bq/m³. The average indoor radon concentration in one area located at the edge of the Aja Mountain in Hail city was 111 Bq/m³. The elevated indoor radon concentrations in many dwellings in the Hail region, prompted us to measure outdoor ground radon in such locations using gas monitor. It was found that radon concentrations at a depth of 0.5 m varied significantly from place to place ranging from 1.2 to 177 kBq/m³. The outdoor radon concentrations are generally correlated with the indoor radon measurements. Radon exhalations from construction materials and soil samples from the Hail region were also measured. It was found that radon exhalations from soil samples are higher than that of construction materials by a factor of at least 3 and reaching up to 11. These results indicate that soil is the main source of indoor radon. Geological interpretations of the results are also given.     

Radon soil–gas as a geological mapping tool: case study from basement complex of Nigeria

In an effort to quantify the geogenic radon soil–gas potential and appraise the use of radon technique as a geological mapping tool in a crystalline basement rock terrain of Ile–Ife Nigeria, radon measurement concentration were made using a radon detector instrument (EDA RD-200) that measures radon isotopes by a scintillator cell coupled to a photomultiplier tube. The data were collected from soils derived from three different lithologic rock units. The observed values were then correlated with the geology of the area. Significant differences in the radon soil–gas concentrations among the three geologic units were observed. Granite gneiss has the highest concentration, followed by grey gneiss and mica schist in that order. The geometric mean (GM) concentration of radon-222 measured in soils directly overlying the three different rock types were 301.4 pCi/l for granite gneiss, 202.8 pCi/l for the grey gneiss, and 199.4 pCi/l for mica schist. Conversely, the average values for radon-220 averaged 1510.0, 815.4, and 733.0 pCi/l for granite gneiss, grey gneiss, and mica schist rocks, respectively. Statistical t test (α=0.05) results indicated that there was no significant difference in the geometric mean of radon soil–gas measured between low and medium potential zones. However, significant differences were found between the low and high radon potential zones, and between the medium and high zones. The low concentrations of radon soil–gas emission observed in this study is explained in terms of the seasonal variation due to thermal convection fluid movement, while the radon concentrations were found to be controlled by the lithology and geochemistry of the underlying bedrock.     

环境中氡及其子体的危害与控制

简要回顾氡致肺癌的长时间认识过程和研究历史,简述了当年铀矿工人和矿工吸入氡及其子体与肺癌发病率的关系,指出环境中氡的危害。重点讨论了国内外室内氡和地下建筑物中氡浓度分布及其来源,从而启发人们研究环境中氡的地质来源以及控制室内氡水平的基本措施;进一步阐述了我国室内氡研究的成果和需要进一步研究的问题。     

Radon reduction in homes constructed on saprolite in the Central Appalachians

 A 3-year study of indoor radon in more than 1000 homes in northern Virginia and southern Maryland was conducted using 3-month exposure alpha-track monitors. In a study set of 200 homes, first-floor indoor radon concentrations, which most closely approximates home exposure levels, averaged slightly more than 3 pCi/l. In a study set of 100 homes, sub-slab ventilation was used to reduce indoor radon concentrations. Interest in remediation was related to public perception of the hazardous nature of radon; people living in homes with indoor radon measurements of more than 4 pCi/l were more likely to participate in the remediation phase of the project. Sub-slab ventilation was successful in more than 90% of the homes in reducing indoor radon from concentrations as high as 30 pCi/ to less than 4 pCi/l, at least for the entire year of post-remediation radon measurements. Received: 29 February 1996 · Accepted: 29 May 1996