From radon hazard to risk prediction-based on geological maps,soil gas and indoor measurements in Germany

Mapped geological units can be regarded as proxies standing for a complex series of subsoil geochemical and physical properties including the assigned radon activity concentration in soil gas, which is taken as best estimator of the regional geogenic radon potential. Areal distribution of measuring sites for soil gas in Germany is adapted to spatial variation of geology. A grid-based and distance-weighted interpolation procedure is applied, following geologically defined neighbourhood relations of measuring sites and accounting for isolated outcrops of known geology but without measurements. To investigate the statistical relationship between indoor radon, house type and building ground specifications, measurements of the indoor radon concentration have been carried out in more than 10,000 dwellings in different regions of Germany. Multiple regression analyses of variance reveal that besides region-specific geological properties and building characteristics, various house type and living style variables significantly contribute to the explained variance for ground floor radon concentrations. These parameters are also dominant in controlling the radon transfer relation from soil gas to indoor air. Risk prediction maps for radon in houses indicating the probability to exceed certain indoor threshold values can be useful especially for regions with no or only a few measurements of indoor radon.     

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.     

Indoor radon probability calculated from the Czech soil gas radon data in a grid net for the European Geogenic Radon Map construction: test of feasibility

The construction of the European Geogenic Radon Map in a proposed grid system 10 × 10 km requires the data test to derive the probability of exceeding the indoor action level 200 Bq m⁻³ from the geologically based data. The Czech Republic disposes both indoor and soil gas data sets to test the real probability to exceed 200 Bq m⁻³ from indoor radon measurements and to compare it with the probability calculated from soil gas radon concentrations. Comparison of real and calculated probability enables to delineate the areas, where under- or overestimation can be expected. The results of data processing show minor differences between processing the raw data in generalised polygons of geological units and in a grid net, when using the generalised geological characteristics of grid cells.     

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.     

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 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.     

Soil radon,permeability, and indoor radon prediction

Attempts to predict which geographic areas should be associated with a high percentage of homes with unusually high indoor radon levels have been based on estimates of soil radon and soil permeability for geological units. In northern Virginia and southern Maryland, it appears that predictions of indoor radon based on estimates of homesite soil radon and soil permeability are very useful.     

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。     

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.     

Development of an indoor radon risk map of the Walloon region of Belgium,integrating geological information

A radon risk map for the Walloon region of Belgium, based on the two databases available, has been calculated and is presented in this work. The data are organized into geological units. For each unit, an average logarithmic standard deviation is calculated, after correcting the higher variability of short term data. The region is divided with an 1-km grid. For each node, the local geological unit is determined, as well as the corresponding logarithmic standard deviation. The logarithmic mean is evaluated by smoothing the data belonging to the same geological unit as the node. Assuming a log-normal distribution, a map that shows for each node the predicted percentage of buildings with an indoor radon concentration above the Action level (400 Bq/m³) is constructed. This is the first radon risk map for this region that fully takes into account the geological information.     

High resolution multispectral satellite data interpretation and limited ground checking: A proxy for geological mapping and uranium exploration in Mahakoshal Fold Belt of Son valley area,Madhya Pradesh

This research aims at integrating remote sensing data and field studies to prospect for uranium mineralisation in the Palaeoproterozoic Mahakoshal Group of rocks in the Son valley area, Central India. In present work, a revised geological map of Mahakoshal Fold Belt (MFB) bounded by Son-Narmada north fault (SNNF) and Son-Narmada south fault (SNSF) along Chorhut-Sidhi-Chitrangi sector falling in Sidhi, Rewa and Shahdol districts of Madhya Pradesh has been prepared based on interpretation of digitally enhanced satellite images. The satellite image interpretation is supported by limited field works, radioelemental measurements (eU, eTh and % K) of in-situ rocks by four channel Portable Gamma Ray Spectrometer (PGRS) and existing published geological maps of Geological Survey of India. In search for mineral potential areas, accurate and up-to-date geological maps are essential as it represent the most basic information for carrying out further exploration activities. However, available geological maps of MFB and sedimentary formations ofVindhayan Supergroup along SNNF and Chhotanagpur Granite Gneissic Complex (CGGC) and Gondwana Supergroup along SNSF available in public domain are discontinuous and multi-scaled.     

A guideline for the evaluation of the soil radon potential based on geogenic and anthropogenic parameters

Following a brief review about radon (²²²Rn) in soils, this study gives a compilation and evaluation of important parameters of the soil ²²²Rn potential. Because investigations of the potential are usually limited to rural areas, anthropogenic or urban effects have not attracted much attention so far. Measurements within the densely populated Ruhr district (Germany) present some new insights into geogenic and anthropogenic parameters on the soil ²²²Rn potential. According to their importance, seven parameters were strung in aranking system, which can be applied in both rural and urban areas: made grounds, geology, relief, vegetation cover, tectonics, soil sealing, traffic vibrations. While the first four parameters control the soil ²²²Rn potential on a more regional scale, the last three can modify it locally. Furthermore, an evaluation of the potential within a ten-point-system is proposed. The advantage of the system lies in the possibility to estimate the soil ²²²Rn potential of any site on a local scale. Common classifications and rankings, based on insufficiently scaled maps, can be included in the proposed system.     

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.     

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.     

Porphyry copper potential mapping using the weights of evidence model in a GIS,northern Shahr e Babak,Iran

A variety of spatial geological data were compiled, evaluated and integrated to produce a potential map for porphyry copper deposits in the northern Shahr e Babak, Iran, within a total area of approximately 408 km². Remotely sensed data including LANDSAT Thematic Mapper were used to create the hydrothermal alteration haloes around intrusive bodies. Geological data, such as exposed granitic to intermediate intrusions, and part of the lineaments were extracted from available geological maps. Aeromagnetic data were also used to extract magnetic anomalies and extra lineaments. The Conditional Independence test was carried out on five binary maps representing diagnostic deposit recognition criteria, and four of them were then integrated using a weights of evidence model. The procedure generated a posterior probability map identifying favourable areas for porphyry copper deposits. The final map highlights the most important known copper deposits in high favourability domains. Some new target areas are also located in the favourability map and warrant further investigation.     

北京广东典型地区室内氡气浓度与地质背景关系

为了解不同地质背景条件室内氡浓度水平,采用脉冲电离室测氡仪AlphaGUARD测量了北京广东不同地质背景典型测点的室内氡浓度,同时对广东某一测点进行了长期的室内氡监测。测量和研究结果表明：地表岩性是影响室内氡浓度高低的重要因素之一。地处花岗岩地区的建筑物内氡浓度高于其他岩性地区的室内氡浓度,广东室内氡水平明显高于北京地区,广东北京花岗岩地区的平均室内氡浓度分别为69.98 Bq/m^3和43.97 Bq/m^3,第四系覆盖地区的平均室内氡浓度分别为43.60 Bq/m^3和35.74 Bq/m^3。民用住宅卧室内的室内氡浓度略高于公共建筑物办公室内的室内氡浓度。因此,结合地质背景研究室内氡的水平与分布对指导开展室内氡调查中确定抽样方案、选择测点及进行区域尺度室内氡评价有重要的实用价值。     

Evaluating the sensitivity of DRASTIC using different data sources,interpretations and mapping approaches

When used in a comprehensive risk assessment framework, aquifer vulnerability maps are a tool to identify the relative susceptibility of the groundwater from sources of contamination at the land surface. The DRASTIC method was designed for use over large areas with a wide variety of geological and hydrogeologic settings as a screening tool in groundwater protection and management. In this study, a series of vulnerability maps were made for the Greater Oliver area, in south central Okanagan, British Columbia, Canada, to test the sensitivity of the methodology to changes in input data type, interpretation, and mapping approaches. The study also illustrates how DRASTIC can be modified for use in areas of limited geological variability, where it may be important for smaller-scale changes in vulnerability to be recognized. Maps were produced using the original DRASTIC rating tables, a set of expanded tables using the original properties but modified ranges to accommodate the variability of data in the valley bottom region, and alternate tables, with modified properties and ranges. Differences in vulnerability rating for the maps using selected combinations and data interpretations are compared to the map using original DRASTIC rating tables using visual and statistical methods. One map was generated using expert hydrological knowledge. The modified tables allowed a greater amount of variability to be expressed in the valley bottom area compared to using the original tables and methods, and could provide a reasonable approach for assessing local scale variability for source water protection planning.     

Maps of the natural environment''s potential in West Germany and Norway as an aid for mineral resources management and protection

Mattig, U., 1990. Maps of the natural environment's potential in West Germany and Norway as an aid for mineral resources management and protection. Eng. Geol., 29: 321–331.

The applied geosciences are of increasing importance for finding an answer to many current problems in spatial management and environmental protection.

Based on the problem of an intelligent use of the geopotential, the paper deals with the achievement and optimization of an appropriate concept for designing geoscientific maps of the natural environment's potential, relevant to areal planning, by comparing a densely populated country like Germany and a more sparsely populated country like Norway. The study carried out is following the example of a map for reserve areas for mineral resources/near surface raw materials—sand and gravel—which enables a comparison and an assessment of the translation of information, relevant to land-use planning, in both countries.

The appropriateness of the interpretation of geoscientific information is ensured by drafting a comprehensive, clearly arranged cartographic presentation, for which uniform and comparable methods, criteria and standards will be developed. The basic concepts of areal planning have to be simple, distinct, adaptable and capable of development. They should enable the geoscientist to contribute his complex and expert knowledge to decisions of regional planning and spatial management.     

Potential groundwater recharge zones within New Zealand

Water resources in New Zealand are not evenly distributed across the country which makes it difficult to adequately allocate the use of water resources in every basin. Groundwater is a fundamental water resource in New Zealand for agricultural, industrial and domestic use. Detailed knowledge regarding groundwater recharge potential is a pre-requisite for sustainable groundwater management, including the assessment of its vulnerability to contamination by pollutants. In this study, a comprehensive GIS approach was used to map the potential groundwater recharge zones across New Zealand. National data sets of lithology, slope, aspect, land use, soil drainage and drainage density were converted to raster data sets with a spatial resolution of 500 m × 500 m and superimposed to derive groundwater potential zones. The resultant maps demonstrate that the potential is low in urban and mountainous areas, such as the Southern Alps, whereas the highest potential can be found in regions with large lakes and in the lower elevation plains areas, where Quaternary sediments prevail. The resulting maps can be used to identify areas of high nutrient leaching in zones where high groundwater recharge potential exists.     

Spatial distribution mapping and radiological hazard assessment of groundwater and soil gas radon in Ekiti State,Southwest Nigeria

Groundwater constitutes the major source of utility water in Ekiti State with the majority of the population depending on groundwater for drinking and other household uses. Soil in the area is commonly used as a component of building materials, which may produce radon in the indoor environment. Excessive concentrations of radon in water and soil can cause radiological health risks to human as witnessed by the increased cases of lung cancer among non-smokers in Nigeria, which may be traceable to the ingestion and inhalation ²²²Rn in drinking water and indoor air. In the present study, comparative in situ measurements of radon in groundwater and soil gas were carried out at one hundred selected locations across the Ekiti State in southwest Nigeria, using a RAD7 radon detector to generate a radon distribution map and to estimate radiation hazards due to radon. The concentrations of radon in groundwater ranged from 0.9 to 472 Bq L^?1 with a mean of 34.7?±?4.4 Bq L^?1, while those of soil gas ranged from 0.1 to 315 kBq L^?1 with a mean of 38.9?±?1.4 kBq L^?1. The total annual effective dose due to inhalation and ingestion of radon in groundwater amounted to 94.7 µSv year^?1, which is lower than the reference dose of 100 µSv year^?1 recommended by the World Health Organization (WHO). The radon map generated for groundwater and soil gas identified three distinct areas with radon levels ranging from low to high. The results of this study show that some locations (Emure, Gbonyin, Ijero and Ikole) show mean total annual effective doses which are higher than the recommended limit. It can then be inferred that the groundwater samples pose significant radiological hazards to the population and that the noticed increase in lung cancer cases may be attributed to the consumption of groundwater in the area.