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1.
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.  相似文献   

2.
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.  相似文献   

3.
Radon buildup in homes is now recognized throughout the world as a potentially major health hazard. The U.S. Nuclear Regulatory Commission and the U.S. Environmental Protection Agency estimate 8,000–30,000 fatalities per year in the United States due to indoor radon. The Albuquerque, New Mexico area was chosen for study because it is representative of metropolitan areas in the southwestern United States where slightly uraniferous source rocks (Sandia granite) have provided the very immature soil for much of the area. The granite contains 4.7 ppm U, and limestone capping the granite 5.7 ppm U. Soils in the area average 4.24 ppm U, and Th/U ratios average 3.2. These data suggest some removal of U from the source rocks, but fixation of the U in the soils (that is, as opposed to widespread removal of the U by solution), thus providing a ready source for soil radon. A pilot study of soil radon in the area in winter of 1983–1984 shows high values, 180 pCi/l, relative to the U.S. average (about 100 pCi/l). In the winter of 1986–1987, 180 dwellings were surveyed for their indoor radon levels, including 20 that had been surveyed in summer of 1986. Twenty-eight percent of those in the winter study yielded indoor radon above the EPA suggested maximum permissible level of 4 pCi/l air, well above the EPA estimate of 10–15 dwellings for the U.S. The indoor radon levels show positive correlation with closeness to the Sandia Mountains, to soil radon, to excess insulation, to homes with solar capacities, and other factors. Building materials may provide a very minor source of some indoor radon. Summer readings are lower than winter readings except when the houses possess refrigerated air conditioning.  相似文献   

4.
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.  相似文献   

5.
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.  相似文献   

6.
 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  相似文献   

7.
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.  相似文献   

8.
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.  相似文献   

9.
The levels of Rn-222 in homes located in Fairfax County, Virginia, and Montgomery County, Maryland, are currently being measured during four consecutive three-month seasonal intervals using alpha-track detectors. Significant variations occur between parts of northern Virginia and southern Maryland because the area is part of three very different geologic provinces. Results from the winter period in these three provinces show that the indoor radon levels were about twice as high as anticipated. Approximately 45 percent of the homes had winter indoor radon levels above 4 pCi/l, the EPA’s recommended action level, and in the spring period, more than 30 percent of the homes still had indoor levels above 4 pCi/l. Indoor radon variations due to seasonal control were about as significant as geological control. Worst-case combinations developed over some rock units in the winter, producing areas in which about 70 percent of the homes exceeded 4 pCi/l.  相似文献   

10.
本文是为了确定在卢氏盆地内被第四系覆盖的黄村断裂的位置、断裂性质,分析黄村断裂与其北侧的乔家窑地热异常的关系。断裂构造是深部氡气汇集和迁移的主要通道,氡气沿断裂向上迁移,在地表浅部形成氡异常。土壤氡气异常可揭示隐伏断裂构造的位置、产状和活动性。黄村断裂通过卢氏乔家窑一带,为第四系沉积物所覆盖。沿垂直断裂走向方向布置4条测线。应用瞬时土壤测氡仪进行了野外现场测量,测试了土壤氡气浓度,确定土壤氡气异常,分析黄村断裂位置、产状和活动性。结果表明:黄村断裂带上方土壤氡气具有异常显示,异常位置与断层位置具有较好的一致性。沿QJ12测线,从南向北,土壤氡气异常形态为低-高-较高-较低-低的峰值形态。在断层带上方氡气峰值异常高于背景值的1.5倍以上,异常峰多数为2个测点以上组成。土壤氡气变化特征表明黄村断裂具有较强的活动性。利用土壤氡气异常分析了黄村断裂深部结构特征,给出了主断裂面与次级断裂面产状和位置。结合土壤氡气异常,分析了乔家地热形成机理。初步研究结果表明,豫西基底构造具有多期活动性,活化区域内的压扭性断裂,可转变为局部张性断裂,控制水热、成矿物质的迁移和富集。  相似文献   

11.
Fracture and fault networks are conduits that facilitate groundwater movement in hard-rock terrains. Soil-gas helium emanometry has been utilized in Wailapally watershed, near Hyderabad in southern India, for the detection of fracture and fault zones in a granite basement terrain having a thin regolith. Based on satellite imagery and geologic mapping, three sites were selected for detailed investigation. High spatial resolution soil-gas samples were collected at every one meter at a depth of >1.5m along 100m long profiles (3 in number). In addition, deep shear-wave images were also obtained using the multichannel analysis of surface waves. The study clearly indicates several soil-gas helium anomalies (above 200 ppb) along the profiles, where the shear-wave velocity images also show many near-surface vertical low velocity zones. We thus interpret that the soil-gas helium anomalous zones and the vertical low-velocity zones are probable traces of fault/fracture zones that could be efficient natural recharge zones and potential groundwater conduits. The result obtained from this study demonstrates the efficacy of an integrated approach of soil-gas helium and the seismic methods for mapping groundwater resource zones in granite/gneiss provinces.  相似文献   

12.
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.  相似文献   

13.
Soil-gas radon concentrations and exhalation rates have generally been observed to be anomalously high along active faults in many parts of the world. The soil-gas method is based on the principle that faults and fractures in rocks are highly permeable pathways along which gases can migrate upward from deep crust and mantle to soil cover, retaining their source signatures. The present study summarizes the influence of fault zones on anomalous radon concentrations in soil by integrated geophysical and geo-structural analyses in three study areas of Central-Northern Calabria (Southern Italy). Soil-gas radon surveys have been carried out by means of an alpha scintillation counting system, at 12,509 locations between 2002 and 2004. A geostatistical approach has been used to estimate the spatial distribution of soil radon concentrations. Relations among soil-gas distribution and geo-structural features have been evaluated by ordinary multi-Gaussian kriging. Highest soil radon concentrations (ca. 90 kBq m?3) have been measured in the Rossanese sector. In the three study areas, no appreciable differences can be noticed among lithotypes, with the highest concentration values (ca. 89 kBq m?3) measured in alluvial deposit and in clay. Measurements of soil-gas radon reveal anomalies clearly connected to the tectonic structures. Increased signals are linearly distributed along regional WNW–ESE trending shear zones, with main pathways of concentration also recognizable along the E–W fault system in the Rossanese sector, the N–S fault system in the Crati Graben and the Catanzaro Trough, and the NE–SW fault system in the Catanzaro Trough. The distribution of epicentres of historical earthquakes occurred between 1184 and 2001 confirms the recent activity of the same fault systems. Soil-gas radon concentrations generally increase, as expected, with decreasing distance to the faults.  相似文献   

14.
 Radon concentrations were measured in soil, air and groundwater in Bhilangana Valley, Garhwal Himalaya, India by using an LR-115 plastic track detector and radon emanometer. Radon concentrations were found to vary from 1 KBq/m3 to 57 KBq/m3 in soil , 5 Bq/l to 887 Bq/l in water and 95 Bq/m3 to 208 Bq/m3 in air. The recorded values are quite high due to associated uranium mineralization in the area. Radon concentration was also found to depend on the tectonic structure and geology of the area. Received: 22 July 1996 · Accepted: 8 January 1997  相似文献   

15.
 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  相似文献   

16.
High indoor radon in approximately 30 percent of private dwellings in the Albuquerque, New Mexico area has been reported previously. The present study explains the areas of high indoor radon as a function of different soil and/or bedrock in the area. Soils were sampled during summer and winter periods using alpha track radon detectors. The values range from 40 to 890 pCi/I air at a depth of 38 cm. The gross mean average is 360 pCi/I for the area for summer readings and 200 pCi/I for winter readings; both values are well over the average U.S. soil radon values of approximately 100 pCi/I. Analyses of soil uranium show a range in values of 1–6 ppm, with a mean of 3.1 ppm. Thorium values range from 3.3 to 28.8 ppm, and Th/U ratios range from 2.9 to 4.6.These values for U, Th, and Th/U suggest that soil U and Th are close to the values reported for the Sandia granite, the source of most of the pediment on which Albuquerque is built. Soil infiltration rates range from ~6 × 10–4 to 4.5 × 10–3 cm/sec for the samples, and soil moisture content ranges from 1.4 to 7.2 percent. A fair correlation of summer soil radon with infiltration rate is noted. Correlation of soil radon with moisture content and/or with percent silt, silt + clay, clay size fraction material is not established by this study. Soil radon values do correlate with regions in the Albuquerque area where high indoor radon is common. A better correlation of high indoor radon values with soils developed immediately over bedrock is observed. Furthermore, all values of average soil and indoor radon increase significantly with proximity of the stations to the Sandia Mountains. Soil uranium also shows this trend. The data argue that regions of potentially high radon can thus be identified.  相似文献   

17.
研究了广东省四家温泉宾馆室内温泉水及其使用过程中对氡浓度的影响。利用RAD-7测氡仪和NR667A测氡义连续测量室内外氡浓度和水氡浓度,发现室内氡浓度受地基土壤、建筑物类型、利用方式(是否洗浴、洗浴时间长短等)、通风状况等诸多因素的影响。无人入住时宾馆室内氡浓度的变化说明土壤氡的渗入是底层房间室内氡的重要影响因素。当在浴室内使用温泉水洗浴时,浴室内平均氡浓度比没有用温泉水时高出1～8．3倍,客房内氡浓度比没有用温泉水洗浴时高出1．2～8．3倍。在使用温泉水时,某些宾馆室内氡浓度超标,可能对宾馆工作人员造成潜在的健康危害,应采取管理措施或技术手段降低其暴露水平。  相似文献   

18.
Measurement of soil-gas radon in some areas of northern Rajasthan,India   总被引：1，自引：0，他引：1  
The health hazards of the radioactive gas radon on general public are well known. In order to understand the level and distribution of 222Rn concentrations in soil-gas in Sri Ganganagar district of Rajasthan, a 222Rn survey was carried out for the first time using RAD7, an electronic radon detector manufactured by Durridge Company (USA), at different locations covering a total area of 10,978 km 2, having a population of approximately 20 lakh. The measurement of 222Rn concentration in soil-gas was carried out at four different depths (10, 40, 70, and 100 cm). The radon concentration in soil-gas for 10, 40, 70, and 100 cm depths ranged from 0.09–4.25, 0.15–6.30, 0.50–9.18, and 0.72–10.40 kBq m ?3, respectively. The minimum value of radon concentration is observed in 33 GB village at 10 cm depth and maximum for Mohanpura village at 100 cm depth. As expected, our data show an increase of soil-gas radon concentration levels with depth. The present results are compared with the available radon data from other studies.  相似文献   

19.
Radon is a naturally occurring colourless and odourless radioactive gas that is soluble in water and is the main source of radioactivity of groundwater. Use of radon contaminated groundwater increased the radon levels in the air, especially in poorly ventilated houses, which is hazardous to health. Ingestion of such water for quite long period may lead to stomach cancer. The drinking water standards proposed by the Bureau of Indian Standards (BIS) exclude the permissible concentration of radon in drinking water. The US Environmental Protection Agency (USEPA) in 1991 proposed a Maximum Concentration Level (MCL) of 11.1 Bq/l for public water supply. The water samples from the bore wells in Tumkur district of Karnataka show radon concentrations in the range of 5 to 250 Bq/l. Ninety percentages of the samples show radon levels above the permissible limit as per USEPA. The spatial variation and geological control over radon concentration in groundwater in the area and sampling sensitivity are discussed here. The study was conducted during March 2012.  相似文献   

20.
Indoor radon mapping and its relation to geology in Hungary   总被引：2，自引：0，他引：2  
Indoor radon mapping may show stronger dependence on geological formations if the measured homes are one-storied houses with no basement. In Hungary, 17,244 homes were investigated on the yearly average of indoor radon concentrations; among these homes, there were 6,154, one-storied, no-basement houses. In Hungary, 21 geological units were created relevant for indoor radon index characterized by lithology, the position of the ground water table, and the gas permeability. Maps were drawn of different topography (counties, grid, geological units) and different values (maximum, mean, indoor radon indexes). A kind of standardization of houses was that only the one-storied, no-basement ones were chosen, but from geological point of view some more information was gained when the wall materials (bricks or adobe) were also taken into account. (“Adobe” is made of clay and straw in Hungary, and not burned as brick, just dried on sunshine). Enhanced indoor radon values can be observed on the bedrock of Cenozoic volcanic rocks and their eroded materials deposited on the local alluvial valleys. Another group with relatively increased indoor radon values can be connected to granite bodies. The grid method is useful for covering large state or even continental areas. For practical public use and detailed radon risk mapping geological or administrative unit-systems could yield more reasonable and useful results.  相似文献   

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