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.     

氡气灾害调查的一些结果

氡气灾害是一种广泛分布的地质灾害。室内氡气浓度偏高会使居民患肺癌的几率增高，而室内氡气主要来自房屋地基所在的地质单元。笔者在美国犹他大学研究所工作期是，研究了瑞丁普朗花岗片麻岩带近地表氡的浓度与铀含量的关系以及铀的分布与居民癌症死亡率之间的相关关系。铀的区域性分布是利用航空伽马能谱测量资料求得的，说明利用航空伽马能谱测量资料开展氡气灾害区域评价的可能性。文中还举例说明氡气调查在制定建设规划方面的作     

Indoor radon mapping and its relation to geology in Hungary

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.     

Uranium mineralization in the Alum Shale Formation (Sweden): Evolution of a U-rich marine black shale from sedimentation to metamorphism

The Alum Shale Formation is a metal-rich black shale, deposited on the Baltoscandian platform between Middle Cambrian and Early Ordovician. These black shales may be of particular economic interest for their relatively high uranium content (100–300 ppm) and their wide distribution from Norway to Estonia. Scandinavian Alum Shale may thus constitute a great potential resource of uranium, as a low grade ore. The Alum Shale Formation is particularly interesting to study the mineralogical expression and content of uranium in series submitted to progressive burial and metamorphism. For this purpose, the behavior of U, P, Ti and organic matter was studied on a series of representative samples from most Alum Shale prospection zones. In southern Sweden, where Alum Shale underwent fairly shallow burial, uranium concentrations have no mineralogical expression except a rather high U content of biogenic phosphates. Calcite concretions (beefs) and fractures recorded the migration of hot overpressured hydrocarbons and brines from thermally mature areas to immature Alum Shale. However, thermal maturation and fluid migration did not allow remobilization of uranium and metals. At the opposite, in northern Sweden, where the series were folded, duplicated and submitted to low grade Greenschist metamorphism during Caledonian orogeny, phospho-silicates U-Si-Ca-P (±Ti ±Zr ±Y) and minor amounts of uraninite are identified and indicate that U, P, and Ti were mobile and precipitated as new phases. The effect of metamorphism is therefore important to consider as the leachability of U, especially during (bio)-hydrometallurgical processes, which will be by far different between the two considered areas.     

Correlation of soil radon and uranium with indoor radon in the Albuquerque,New Mexico area

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.     

断层上方第四系覆盖层中氡气运移规律的数值模拟

在前人研究的基础上,建立了稳定条件下断层上方第四系覆盖层中氡气的运移方程,给出了相应的边界条件,对断层上方覆盖层中的氡浓度分布进行了数值模拟,并对其影响因素进行了讨论.结果表明,断层上方第四系覆盖层中存在明显的氡浓度异常,其分布与覆盖层的厚度、断层的宽度、氡的扩散系数和对流速度等因素有关.     

Pollutant transport in a shallow unconfined aquifer in Perry,Ohio

The groundwater system in northern Perry Township in Lake County, Ohio, is a shallow, unconfined aquifer consisting of periglacial lake beach deposits and less permeable lacustrine plain deposits. Groundwater flow is generally toward Lake Erie from south to north and is controlled by the top of the Ashtabula Till, but strong, local variations are caused by northward flowing streams During the study period, water levels in most wells exhibited a seasonal fluctuation of less than 0 3 m from their mean values. The areal distributions of chloride and nitrate concentrations indicate that road salt runoff easily infiltrates the aquifer and that nitrate may be sourced from fertilizer application. Ground-water flow and solute transport models indicate that in excess of 27 years are required to obtain chemical steady-state under hydrologic steady-state conditions. The simulations also demonstrate that nitrate loading must occur in more than one cultivated field in order to obtain the observed wide-spread nitrate distribution.     

Geology of the Devonian black shales of the Appalachian Basin

Black shales of Devonian age in the Appalachian Basin are a unique rock sequence. The high content of organic matter, which imparts the characteristic lithology, has for years attracted considerable interest in the shales as a possible source of energy. The recent energy shortage prompted the U.S. Department of Energy through the Eastern Gas Shales Project of the Morgantown Energy Technology Center to underwrite a research program to determine the geologic, geochemical, and structural characteristics of the Devonian black shales in order to enhance the recovery of gas from the shales. Geologic studies by Federal and State agencies and academic institutions produced a regional stratigraphic network that correlates the 15 ft black shale sequence in Tennessee with 3000 ft of interbedded black and gray shales in central New York. These studies correlate the classic Devonian black shale sequence in New York with the Ohio Shale of Ohio and Kentucky and the Chattanooga Shale of Tennessee and southwestern Virginia. Biostratigraphic and lithostratigraphic markers in conjunction with gamma-ray logs facilitated long-range correlations within the Appalachian Basin. Basinwide correlations, including the subsurface rocks, provided a basis for determining the areal distribution and thickness of the important black shale units. The organic carbon content of the dark shales generally increases from east to west across the basin and is sufficient to qualify as a hydrocarbon source rock. Significant structural features that involve the black shale and their hydrocarbon potential are the Rome trough, Kentucky River and Irvine-Paint Creek fault zone, and regional decollements and ramp zones.     

Application of logistic regression model for slope instability prediction in Cuyahoga River Watershed,Ohio, USA

High incidences of slope movement are observed throughout Cuyahoga River watershed in northeast Ohio, USA. The major type of slope failure involves rotational movement in steep stream walls where erosion of the banks creates over-steepened slopes. The occurrence of landslides in the area depends on a complex interaction of natural as well as human induced factors, including: rock and soil strength, slope geometry, permeability, precipitation, presence of old landslides, proximity to streams and flood-prone areas, land use patterns, excavation of lower slopes and/or increasing the load on upper slopes, alteration of surface and subsurface drainage. These factors were used to evaluate the landslide-induced hazard in Cuyahoga River watershed using logistic regression analysis, and a landslide susceptibility map was produced in ArcGIS. The map classified land into four categories of landslide susceptibility: low, moderate, high, and very high. The susceptibility map was validated using known landslide locations within the watershed area. The landslide susceptibility map produced by the logistic regression model can be efficiently used to monitor potential landslide-related problems, and, in turn, can help to reduce hazards associated with landslides.     

Organic geochemistry of the kerogen and bitumen from the Ohio Shale by pyrolysis-gas chromatography

An exposure of the Ohio Shale at Bristol Ridge, Ohio in the Bellefontaine Outlier was sampled into 53 channel units. Proximate and elemental (CHN) analyses were performed on these samples to determine the concentration of organic matter. The organic content averaged 6.82% with the highest both in the lower half (11.08%) and extreme upper part (10.43%) of the section.Fragmentation of the kerogen of each of the whole rock samples was accomplished by pyrolyzing for 10 s at 750°C in the injection port of a gas chromatograph with a FID detector. The concentration and distribution of the diagnostic hydrocarbons fragmented at this temperature were used to infer the molecular construction of the high molecular weight kerogens. The suite of identified hydrocarbons for each of the samples throughout the section was similar, but a very large fluctuation in the amount of pyrolysis products was observed. This fluctuation is strongly related to organic richness as defined by the proximate and elemental analyses. The identification of diagnostic normal alkanes and aromatics and SCI indicates that the kerogen assemblage is composed of both marine and terrestial components — most likely a mixed Type II kerogen. The contribution of individual aromatic and normal alkanes is variable, which suggests that there were minor fluctuations in the proportions of terrestrial and marine organic matter during decomposition.Bitumen pyrolized from the whole rock and bitumen removed by Soxhlet extraction using a 4:1 benzene/methanol solvent mixture were analyzed. Comparison of these two techniques yield similar pristane/phytane ratios and Carbon Preference Index (CPI) values. On decomposition the whole rock bitumen exhibited a mean pristane/phytane ratio of 1.5 and a mean CPI value of 1.4, whereas the Soxhlet-extracted bitumen exhibited a mean pristane/phytane ratio of 1.6 and a mean value of 1.3. The low pristane/phytane ratios from this outlier indicates a possible marine environment, with reducing conditions existing immediately below the sediment-water interface. The CPI values also indicate the sedimentary sequence is thermally immature. Reflectance of the vitrinite (%R_o 0.05) and fluorescence (Q 0.93) of the algal bodies indicate a maturation at the beginning of the oil window or at boundary between thermal immaturity and maturity.     

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。     

鄂尔多斯西缘羊虎沟组页岩气聚集地质条件分析

为了研究鄂尔多斯盆地西缘羊虎沟组页岩气成藏潜力,根据泥页岩厚度、有机质类型、有机质丰度与成熟度等因素,从暗色泥页岩地层空间展布特征、构造特征与热事件、生烃能力等方面分析页岩气聚集的地质条件。研究表明,羊虎沟组暗色泥页岩单层最大厚度约30m,区内发育的逆冲推覆构造使地层叠置形成厚的泥页岩层段,泥页岩干酪根以III型为主,II—I型也有发育,TOC平均值为3.25%,R0为1%~4%,这些条件均有利于页岩气聚集成藏。综合分析认为呼鲁斯太南部、乌达及石炭井地区为页岩气聚集最有利的区域。     

Comparison of organic geochemistry and metal enrichment in two black shales: Cambrian Alum Shale of Sweden and Devonian Chattanooga Shale of United States

In most black shales, such as the Chattanooga Shale and related shales of the eastern interior United States, increased metal and metalloid contents are generally related to increased organic carbon content, decreased sedimentation rate, organic matter type, or position in the basin. In areas where the stratigraphic equivalents of the Chattanooga Shale are deeply buried and and the organic material is thermally mature, metal contents are essentially the same as in unheated areas and correlate with organic C or S contents. This paradigm does not hold for the Cambrian Alum Shale Formation of Sweden where increased metal content does not necessarily correlate with organic matter content nor is metal enrichment necessarily related to land derived humic material because this organic matter is all of marine source. In southcentral Sweden the elements U, Mo, V, Ni, Zn, Cd and Pb are all enriched relative to average black shales but only U and Mo correlate to organic matter content. Tectonically disturbed and metamorphosed allochthonous samples of Alum Shale on the Caledonian front in western Sweden have even higher amounts for some metals (V, Ni, Zn and Ba) relative to the autochthonous shales in this area and those in southern Sweden.     

不同覆盖物抑制铀尾矿氡析出的效果

对5种不同覆盖物（红土、砂、废石、砂与红土混合物、废石与红土混合物）降低铀尾矿氡析出的效果进行了现场实验研究。结果表明,不同覆盖物的效果存在较大差异,在相同覆盖厚度条件下,氡析出率降低系数是红土〉红土与废石混合物〉红土与砂混合物〉废石〉砂。表面氡析出率随覆盖物厚度增大而减小,氡析出率降低系数的对数与覆盖厚度成正比,所得到的各种覆盖物的拟合线性方程可用来评价覆盖效果。建立了各种覆盖物覆盖厚度估算的经验公式。综合考虑降氡效果、经济成本、生态环境效应,废石与红土混合物是该地区铀尾矿库最佳覆盖物。     

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.     

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     

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.     

Helium in soil and overburden gas as an exploration pathfinder — an assessment

Orientation surveys were conducted over five deposits to test the potential of determining helium in overburden gas as a pathfinder for uranium mineralization and other deposits containing uranium or thorium. Samples were collected via fixed tubes emplaced at depths of 6 m in backfilled holes drilled for this purpose. Compared to the atmospheric background value of 5.24 ppm v/v He, a variable weak anomaly (maximum 5.45–5.65 ppm He) was found over part of the Angela uranium deposit, N.T., in an arid area where mineralization is mostly at a depth of 60–90 m, at or below the water-table. Helium contents were mostly at background levels over a uranium deposit in the Officer Basin, W.A., where mineralization is at the water-table at 30–35 m, although radon gave a marked anomaly. Neither helium nor radon indicated the Manyingee deposit, W.A., which has uranium mineralization in a confined aquifer at 60–110 m. Similarly, no helium anomalies were found over the uranium- and thorium-rich Mt. Weld carbonatite or mineral sands at Eneabba.There appeared to be no correlation between helium distributions shown by groundwater and overburden-gas sampling at Manyingee or Mt. Weld. At Mt. Weld, groundwaters contained 0.06 to 13.60 μ/l He and overburden gases 5.24–5.47 ppm He, with the higher gas concentrations over country rock, where waters had background helium contents. It is presumed that equilibration between overburden gas and the atmosphere is far more rapid than that between overburden gas and groundwater, so that any helium released from the water is quickly dispersed.Overburden-gas helium concentrations were found to vary according to overburden type, being 5.24–5.32 ppm where sandy and porous and 5.30–5.50 ppm where clay-rich and less permeable. These background variations, which are greater than the total background-anomaly contrasts reported in the literature for shallow soil gases, have not been accounted for in most trial surveys, nor has the possibility of similar variations being due to analytical error. From the data obtained, there is little evidence that helium can be considered an effective pathfinder for blind or concealed deposits using soil gas or overburden gas as sample media. Previous work on the use of soil and soil-gas helium determinations in uranium exploration is reviewed in the light of these findings and the concept and techniques assessed.     

应用氡气测量和土壤天然热释光测量推断花岗岩型铀矿含矿部位——以下庄花岗岩型铀矿田为例

文中简要介绍了氡气测量和土壤天然热释光测量（TL）野外样品采集及室内样品分析的工作方法和应注意的事项。对下庄花岗岩型铀矿床的初步研究结果表明：（1）在硅化破碎带型铀矿体上方，氡气测量的高值异常主要反映构造破碎带在地表的出露位置，土壤天然热释光测量的高值异常则主要反映铀矿体的位置，当两种方法的异常重合时，找到铀矿体的可能性较大；（2）在“交点”型铀矿体上方，氡气测量的高值异常同样反映了构造破碎带在地表的出露位置，而土壤天然热释光测量的高值异常则反映了构造破碎带与中基性岩脉的交线处为铀矿体的赋存位置。