浅谈地基土壤中氡浓度的测定及影响因素

本文介绍了地基土壤中氡浓度的测定标准和方法．探讨了实际工作中影响土壤氡测定结果准确性的相关因素。     

广州新建住宅室内氡浓度调查

采用活性炭盒法测量广州地区新建住宅楼室内氡浓度,在对1796个样本进行统计后得到近年来新建住宅室内氡浓度平均值为84.2Bq/m~3,在检测房间中有3%的房间室内氡浓度大于200Bq/m~3。土壤氡浓度对高层住宅室内氡的影响不大。室内氡浓度检测时的状态不同,检测结果也完全不同。     

浅析合肥地区场地土壤氡浓度值分布

文章在简要介绍氡气的危害和检测方法以及检测要求的基础上,依据国家标准规定的土壤氡浓度检测方法,对合肥市数十个新建建筑项目的场地土壤氡浓度进行检测,根据检测数据,探讨合肥市各行政区域内土壤氡浓度分布情况,为绿色建筑的前期规划和设计阶段提供参考。     

合肥地区土壤氡浓度水平调查及影响因素分析

文章通过选取合肥不同区域的多个实际工程案例,使用FD216环境氡测量仪进行现场土壤氡浓度检测,对检测结果进行综合分析,得出合肥地区土壤氡浓度的大致分布情况,并通过检测分析环境因素对土壤氡浓度的影响。     

绍兴城区土壤氡浓度分布特征及分析

《民用建筑工程室内环境污染控制规范（GB 50325-2001）》是民用建筑工程中土壤氡浓度测量的主要依据,通过在绍兴城区开展土壤氡浓度测试、调查工作,把实测结果、地质背景和现场特征分析相结合,分析了绍兴城区土壤氡浓度高背景区的分布特征及形成原因。     

利用检测手段来预防民用建筑工程室内氡的危害

采用美国Durridge公司生产的RAD7型α能谱氡气测氡仪,对3个有代表性的工程土壤中氡浓度、建筑物所用建筑材料的表面氡析出率和最终竣工验收室内环境氡指标的检测,利用检测手段全方位地阐述预防民用建筑工程室内氡的危害。     

谈勘察设计阶段土壤氡浓度控制问题

防氡工程设计类同于防水工程设计,工程设计人员应掌握土壤中氡浓度的情况,必要时应采用有效的工程措施,使土壤氡浓度处于较低水平,从而保证室内氡浓度也降至最低,有利于以后施工及验收工作的进行。     

广州市土壤氡区域背景值及其应用

《民用建筑建筑工程室内环境污染控制规范》要求对建筑场地土壤中的氡浓度进行测定,并根据区域放射性资料确定是否要采取防氡降氡措施,而广州市因尚未进行相关普查故无法提供区域背景值,文中根据广州市的地质和构造特点,结合工程实际提出土壤氡的区域背景值及其应用。     

土壤氡浓度随季节变化规律

介绍了土壤氡浓度的测量方案及仪器,探讨了氡浓度随季节的变化规律以及氡浓度一天的变化规律,并得出了一定的结论,为工程地下防氡设计提供了依据。     

地下工程的防氡通风

七十年代以来,欧美各国为了节省能源,加强了房屋门窗的密闭措施,并减少通风换气次数,结果,房屋内的氡气及其子体浓度升高,造成了对人们的危害,引起了卫生界的重视。我国对地面建筑中氡危害的研究,已开始起步,进行普查;对地下工程中氡的危害,也在着手研究。有些研究部门对一些地下工程进行了氡及其子体浓度的测定,发现有的工程中氡及其子体的浓度很高,比地面建筑高几十倍甚至几百倍,有的比铀矿里的浓度还高得多。因此开发利用人防工程,开发地下空间,就要研究和解决地下工程中的防氡问题。本文着重对地下工程中氡及其子体的允许浓度、氡气浓度与通风的关系以及通风系统在设计、使用过程中应注意的一些问题,提出一些看法。     

Mapping the geogenic radon potential in Germany

Mapping the geogenic radon potential in Germany is a research project initiated by the German Federal Ministry for the Environment, Conservation and Reactor Safety. The project was aimed to develop a standard methodology for the estimation of a geogenic radon potential and to apply this method to map the region of Germany as an overview for planning purposes. The regionalisation results from a distance-weighted interpolation of the site-specific values of radon concentration in soil gas and in situ gas permeability of soils on a regular grid considering the corresponding geological units. The map of Germany in a scale of 1:2 million is based on the radon concentration in soil gas as an estimator of the geogenic radon potential assuming the 'worst case' of uniform highest permeability. The distribution is subdivided into categories of low (< 10 kBq/m3), medium (10-100 kBq/m3), increased (100-500 kBq/m3) and high (> 500 kBq/m3) radon concentration. High values occur especially in regions with granites and basement rocks of Paleozoic age, and are proven by measurements in 0.03% of the total area. Many of these regions are also known for their enhanced indoor values. The class with increased values takes a portion of 7.86% and likewise occurs mainly in regions with outcrops of folded and metamorphic basement, but also of some Meso- and Cenozoic sediments with increased uranium contents and/or higher emanation coefficients. For 67.3% of the country, the radon concentration is classified as 'medium', and an assignment to specific geological units cannot be made at the map scale considered. Low radon contents, where protective measures against radon are usually not considered, are found in the geologically rather homogeneous part of northern Germany with unconsolidated Cenozoic sediments, covering approximately 25% of the total country. It is of course not possible to predict the indoor radon concentration of single houses from these maps, because construction type and structural fabric of houses are essentially governing the extent to which subsoil radon potential affects the indoor concentration. Besides this, in places with site-specific geochemical, structural and soil-physical properties, local radon anomalies may occur which were not recorded in the course of the wide-meshed screening study.     

A test of radon service providers available on the Internet

With the announcement of the Government of Canada's Radon Guideline and increased public awareness of radon risk, more and more Canadians wish to test their homes for radon. Radon service providers available on the Internet have attracted many homeowners' attention. These services provide an easy and less expensive way for homeowners to test radon levels in their homes. However, a question has frequently been asked, 'How reliable are the radon testing services available on the Internet?' To answer this question, we ordered 36 radon testing kits from 10 service providers on the Internet. The test results showed that online radon testing services could collectively meet the performance requirement. However, the quality of a few service providers needs to be improved. PRACTICAL IMPLICATIONS: Indoor radon tests were performed with detectors ordered from 10 service providers available on the Internet. The results showed that online radon testing services could collectively meet the performance requirement. However, the quality of a few service providers needs to be improved.     

Comparison of Northern Ireland radon maps based on indoor radon measurements and geology with maps derived by predictive modelling of airborne radiometric and ground permeability data

Publicly available information about radon potential in Northern Ireland is currently based on indoor radon results averaged over 1-km grid squares, an approach that does not take into account the geological origin of the radon. This study describes a spatially more accurate estimate of the radon potential of Northern Ireland using an integrated radon potential mapping method based on indoor radon measurements and geology that was originally developed for mapping radon potential in England and Wales. A refinement of this method was also investigated using linear regression analysis of a selection of relevant airborne and soil geochemical parameters from the Tellus Project. The most significant independent variables were found to be eU, a parameter derived from airborne gamma spectrometry measurements of radon decay products in the top layer of soil and exposed bedrock, and the permeability of the ground. The radon potential map generated from the Tellus data agrees in many respects with the map based on indoor radon data and geology but there are several areas where radon potential predicted from the airborne radiometric and permeability data is substantially lower. This under-prediction could be caused by the radon concentration being lower in the top 30 cm of the soil than at greater depth, because of the loss of radon from the surface rocks and soils to air.     

Seasonal variations in soil gas radon concentration

We have been studying seasonal variations in soil gas radon concentration in southern Finland since 1982.To detect the radon we employ liquid scintillation solution in an open glass vial placed in a plastic tube set in a hole drilled in the ground.The results from an esker area show that there may be an appreciable seasonal variation in soil gas radon concentration, similar to that in houses. Because of the varying permeability and radium concentration of the ground, small changes in the building may have a large impact.     

Soil gas measurements below foundation depth improve indoor radon prediction

A soil gas measurement method developed earlier, [Nucl Tracks Radiat Meas, 22(1-4) (1993) 468] was applied to boreholes drilled to below foundation depth. Radon concentration and permeability were measured at 50-cm intervals. In radon prone areas, permeability showed an increase with depth over several orders of magnitude, indicating a low permeability top layer with a thickness of 0.5 m and more. A radon availability index (RAI) was empirically defined and the maximum RAI of each boring proved to be a reliable indicator for radon problems in nearby houses. The permeability of the top layer also proved to be an important factor for a better understanding of soil gas transport and the influence of rain. Implications for radon mitigation are derived.     

Determination of radon exhalation from construction materials using VOC emission test chambers

The inhalation of ²²²Rn (radon) decay products is one of the most important reasons for lung cancer after smoking. Stony building materials are an important source of indoor radon. This article describes the determination of the exhalation rate of stony construction materials by the use of commercially available measuring devices in combination with VOC emission test chambers. Five materials – two types of clay brick, clinker brick, light‐weight concrete brick, and honeycomb brick – generally used for wall constructions were used for the experiments. Their contribution to real room concentrations was estimated by applying room model parameters given in ISO 16000‐9, RP 112, and AgBB. This knowledge can be relevant, if for instance indoor radon concentration is limited by law. The test set‐up used here is well suited for application in test laboratories dealing with VOC emission testing.     

Installation of supply/exhaust ventilation as a remedial action against radon from soil and/or building materials

Installation of supply/exhaust ventilation systems is a possible remedial action against excessive concentration of radon. Installations in some 15 one-family houses in Sweden have been evaluated regarding effectiveness, costs and impact on energy demad. This remedial action is most suitable when exhalation from the structure itself is the major source of radon. The resulting decrease in concentration of radon can be estimated from dilution in the increased flow of air through the building. The exhalation from the building materials is constant and unaffected by ventilation rate. When the radon originates from the soil subjacent to the building the inflow of radon is a function of untightness and pressure difference between soil and indoor air. The result of retrofitting a ventilation system will then be the combined effect of dilution and a possible change in pressure difference. The defects in these buildings are normally remedied by more cost-effective action based on sealing the route of entry or depressurising/ventilating the subjacent soil. If a ventilation system is installed, it should preferentially be a balanced supply/exhaust system in order to give a minimal negative pressure indoors.     

A prediction method for radon in groundwater using GIS and multivariate statistics

Radon (222Rn) in groundwater constitutes a source of natural radioactivity to indoor air. It is difficult to make predictions of radon levels in groundwater due to the heterogeneous distribution of uranium and radium, flow patterns and varying geochemical conditions. High radon concentrations in groundwater are not always associated with high uranium content in the bedrock, since groundwater with a high radon content has been found in regions with low to moderate uranium concentrations in the bedrock. This paper describes a methodology for predicting areas with high concentrations of 222Rn in groundwater on a general scale, within an area of approximately 185x145km2. The methodology is based on multivariate statistical analyses, including principal component analysis and regression analysis, and investigates the factors of geology, land use, topography and uranium (U) content in the bedrock. A statistical variable based method (the RV method) was used to estimate risk values related to different radon concentrations. The method was calibrated and tested on more than 4400 drilled wells in Stockholm County. The results showed that radon concentration was clearly correlated to bedrock type, well altitude and distance from fracture zones. The weighted index (risk value) estimated by the RV method provided a fair prediction of radon potential in groundwater on a general scale. Risk values obtained using the RV method were compared to radon measurements in 12 test areas (on a local scale, each of area 25x25km2) in Stockholm County and a high correlation (r=-0.87) was observed. The study showed that the occurrence and spread of radon in groundwater are guided by multiple factors, which can be used in a radon prediction method on a general scale. However, it does not provide any direct information on the geochemical and flow processes involved.     

Temporal variations of radon concentration in the saturated soil of Alpine grassland: The role of groundwater flow

Radon concentration has been monitored from 1995 to 1999 in the soil of the Sur-Frêtes ridge (French Alps), covered with snow from November to April. Measurements were performed at 70 cm depth, with a sampling time of 1 h, at two points: the summit of the ridge, at an altitude of 1792 m, and the bottom of the ridge, at an altitude of 1590 m. On the summit, radon concentration shows a moderate seasonal variation, with a high value from October to April (winter), and a low value from May to September (summer). At the bottom of the ridge, a large and opposite seasonal variation is observed, with a low value in winter and a high value in summer. Fluctuations of the radon concentration seem to be associated with temperature variations, an effect which is largely delusory. Indeed, these variations are actually due to water infiltration. A simplified mixing model is used to show that, at the summit of the ridge, two effects compete in the radon response: a slow infiltration response, rich in radon, with a typical time scale of days, and a fast infiltration of radon-poor rainwater. At the bottom of the ridge, similarly, two groundwater contributions compete: one slow infiltration response, similar to the response seen at the summit, and an additional slower response, with a typical time scale of about a month. This second slower response can be interpreted as the aquifer discharge in response to snow melt. This study shows that, while caution is necessary to properly interpret the various effects, the temporal variations of the radon concentration in soil can be understood reasonably well, and appear to be a sensitive tool to study the subtle interplay of near surface transfer processes of groundwater with different transit times.