Radon anomaly in soil gas as an earthquake precursor.

The mechanical processes of earthquake preparation are always accompanied by deformations; afterwards, the complex short- or long-term precursory phenomena can appear. Anomalies of radon concentrations in soil gas are registered a few weeks or months before many earthquakes. Radon concentrations in soil gas were continuously measured by the LR-115 nuclear track detectors at site A (Osijek) during a 4-year period, as well as by the Barasol semiconductor detector at site B (Kasina) during 2 years. We investigated the influence of the meteorological parameters on the temporal radon variations, and we determined the equation of the multiple regression that enabled the reduction (deconvolution) of the radon variation caused by the barometric pressure, rainfall and temperature. The pre-earthquake radon anomalies at site A indicated 46% of the seismic events, on criterion M3, R<200km, and 21% at site B. Empirical equations between earthquake magnitude, epicenter distance and precursor time enabled estimation or prediction of an earthquake that will rise at the epicenter distance R from the monitoring site in expecting precursor time T.     

Two year evolution of radon emission and tectonic movements in Tuzla Fault,Seferihisar-İzmir

Previous studies showed that tectonic movement and meteorological events are accompanied with radon release. In this study soil gas radon and tectonic movements were investigated with meteorological factors taking into account. Soil gas radon measurements were collected over a-two year period (2008–2010) at the Tuzla Fault in Turkey. The relationship between radon anomalies and seismic activities was evaluated using Dobrovolsky's form. It is shown that not only magnitude of earthquake but also distance from the measurement site should be used for identifying radon anomalies.     

Criteria of radon risk of territories and methods for their determination

The paper analyzes the values used in the assessment of radon potential of territories. It was shown that the most reliable criterion in the assessment of radon risk of territories can be the value of radon activity concentration fixed at large depths. The authors proposed a simple method to assess this value and radon flux density from the soil surface, based on the measurement of radon activity concentration in soil gas at two twice differing depths and the diffusion model of transport.     

土壤物理性质对土壤氡浓度及地表氡析出率的影响

目的探讨土壤性质对土壤氡浓度及地表氡析出率的影响。方法在北京、贵阳、呼和浩特的31个测量点进行土壤氡浓度及析出率的现场实测。采集土壤样品，在实验室进行土壤镭含量、含水量、孔隙度和粒径分布等物理性质测量。用线性拟合方法分析了实测土壤氡、析出率数据之间的相关性，以及它们与土壤镭含量的关系。结果地表氡析出率与土壤氡浓度和土壤镭含量有正相关关系；土壤含水饱和度过高或过低均会使析出率和土壤氡浓度降低；贵阳地区土壤镭含量较高，但其粉砂黏土壤的特性使土壤氡浓度很难准确采样，导致结果偏低。结论地表氡析出率和土壤氡浓度虽然与土壤镭含量有正相关关系，但在实际环境中易受含水量等多因素影响，而且土壤氡浓度的准确测量受土壤特性限制较大。     

A comparison between active and passive techniques for measurements of radon emanation factors

Some radon related parameters have been determined through two different techniques (passive and active) in soil and phosphogypsum samples. Emanation factors determined through these techniques show a good agreement for soil samples while for phosphogympsum samples appear large discrepancies. In this paper, these discrepancies are analyzed and explained if non-controlled radon leakages in the passive technique are taken into account.     

土壤氡析出率影响因素及估算模型

目的通过对某定点处土壤氡析出率的长期测量观察,分析并总结环境因素对氡析出率的影响规律。方法使用ERS-2静电收集式氡采样测量仪,每次采样累积时间40min,每10分钟测量一次氡浓度,通过线性拟和求算出土壤表面氡析出率;利用已有的数学模型对测量结果进行估算和评价;同时测量环境空气的湿度、温度、土壤含水量和土壤氡浓度。结果春季土壤氡析出率平均值为(24·9±5·6)mBq/(m2·s),夏季平均值为(11·9±3·4)mBq/(m2·s)。结论在影响土壤氡析出率的诸因素中,湿度非常重要,而环境温度对氡析出率的影响相对较小;测量期间环境气压变化不明显,没有观测到气压对析出率的影响。开展土壤射气系数的研究,将有助于阐明多种环境因素对土壤表面氡析出率的影响。     

Earthquake precursory studies in Kangra valley of North West Himalayas, India, with special emphasis on radon emission

The continuous soil gas radon monitoring is carried out at Palampur and the daily monitoring of radon concentration in water is carried out at Dharamshala region of Kangra valley of North West Himalayas, India, a seismic zone V, to study the correlation of radon anomalies in relation to seismic activities. In this study, radon monitoring in soil was carried out by using barasol probe manufactured by Algade France, whereas the radon content in water was recorded using RAD 7 radon monitoring system of Durridge Company USA. The effect of meteorological parameters viz. temperature, pressure, wind velocity, rainfall, and humidity on radon emission has been studied. The seasonal average value and standard deviation of radon in soil and water is calculated to find the radon anomaly to minimize the effect of meteorological parameters on radon emission. The radon anomalies observed in the region have been correlated with the seismic events of M≥2 reported by Wadia Institute of Himalayas Geology Dehradoon and Indian Meteorological Department, New Delhi in NW Himalayas within 250 km distance from the monitoring stations.     

Application of decision trees to the analysis of soil radon data for earthquake prediction

Different regression methods have been used to predict radon concentration in soil gas on the basis of environmental data, i.e. barometric pressure, soil temperature, air temperature and rainfall. Analyses of the radon data from three stations in the Kr ko basin, Slovenia, have shown that model trees outperform other regression methods. A model has been built which predicts radon concentration with a correlation of 0.8, provided it is influenced only by the environmental parameters. In periods with seismic activity this correlation is much lower. This decrease in predictive accuracy appears 1–7 days before earthquakes with local magnitude 0.8–3.3.     

Procedures for the determination of 222Rn exhalation and effective 226Ra activity in soil samples.

Two methods for measuring 222Rn exhalation and effective 226Ra in soil samples were studied. In the first determination, the method employed was based on the adsorption of radon onto activated charcoal and subsequent measurement of the activity of its daughters with an HPGe (high-purity germanium) detector. In the second, vials containing an aqueous suspension of the sample, mixed with an insoluble high efficiency mineral oil scintillation cocktail, were measured using a low-level liquid scintillation counter. Studies of optimum sampling time, efficiency in both procedures, variation of 226Ra efficiency with quenching, as well as the effect of sample amount and granulometry upon the quenching parameter, were carried out. The two methods were applied to the determination of 222Rn exhalation and effective 226Ra in environmental samples.     

Temporal variations of radon in soil related to earthquakes.

A radon detector with LR-115 nuclear track film was constructed for radon concentration measurements in soil. Temporal radon variations, as well as the barometric pressure, precipitation and temperature were measured for two years. Negative correlation between radon concentration in soil and barometric pressure was found. For some of the recorded earthquakes that occurred during the observation period, soil radon anomalies may be noticed one month before the quakes.     

Estimation of the radon concentration in soil related to the environmental parameters by a modified Adaline neural network.

A new method based on adaptive linear neuron (Adaline) is used to estimate the radon concentration in soil associated with the environmental parameters. Analysis of the data obtained from a site in Thailand indicates that our proposed method is able to differentiate temporal variation of radon concentration related to the environmental parameters from those caused by phenomena in the earth (e.g. earthquake).The result also shows agreement between our method and another method based on impulse responses from multivariable time series (complex mathematical equations).     

Soil radon monitoring in the NE flank of Mt. Etna (Sicily).

Soil radon has been monitored at a fixed location on the northeastern flank of Mt. Etna, a high-risk volcano in Sicily. The aim of this study was to evaluate the effects of the recent volcanic activity on soil radon concentration. Continuous radon measurements have been performed since July 2001. While comparison between the trend in in-soil radon concentration and the acquired meteorological series (temperature, humidity and pressure) appear to confirm a general seasonal correlation, nevertheless particular anomalies suggest a possible dependence of the radon concentration on volcanic dynamics.     

A short-time method to measure the radon potential of porous materials

The radiological risk associated with the use of solid materials has been traditionally established according to their radon exhalation rates, the accumulation chamber technique being the most widely used for the determination of this quantity. However, this coupled methodology has two important drawbacks: the calculated exhalation rate value depends strongly on the experimental setup used; hence widely varying values can be calculated for the same material. Furthermore, this technique usually requires long monitoring times (between 1 and 4 weeks).In this paper, we present a fast and reproducible method for the determination of radon potential (as an alternative to the exhalation rate) based on the application of the accumulation chamber technique. Radon potential is proportional to the emanation coefficient, and can be calculated within measuring times of less than 24 h. The theoretical basis is developed and the experimental setup is discussed in detail in this paper.The procedures for the determination of different experimental parameters (leakage constant, slope correction) are shown as essential steps for the later determination of the radon potential. In addition, the robustness of the developed methodology is demonstrated, and the reproducibility tests carried out with the general system performance are shown. Finally, the radon potential for different materials is determined, allowing its prompt categorization according to its associated radiological risk.     

Radon diffusion coefficient measurement in waterproofings - A review of methods and an analysis of differences in results

This paper summarizes information about 16 measuring methods for determining the radon diffusion coefficient of waterproofing materials. We have found that the differences in results for identical membranes, which can be as high as two orders of magnitude, can mainly be attributed to insufficient duration of the tests, insufficient radon concentration to which the samples are exposed, and the use of steady state calculation procedures for data measured under non-steady state conditions.     

Soil radon monitoring in the Krsko Basin, Slovenia.

In order to support the safe operation of the Krsko Nuclear Power Plant (Westinghouse, 676 MWe PWR), the seismotectonic structure of the Krsko basin has been thoroughly investigated. As part of a wider study, a study on radon in soil gas was started in April 1999. Combined barasol detectors buried in six boreholes, two along the Orlica fault and four on either side of it, measure and record radon activity, temperature and pressure every 60 min. The results have been evaluated and the possibility of a correlation with seismic activity is discussed. Correlation between radon concentration and barometric pressure has been observed for all barasols. Preliminary results show that, at one location, the correlation coefficient between radon and barometric pressure changed sign before earthquakes.     

Residence time of tropospheric aerosols in association with radioactive nuclides.

The residence time of atmospheric aerosol particles is a function of various removal processes, such as dry deposition by impaction, diffusion, sedimentation and resuspension as well as wet deposition by rain drops (precipitation scavenging). Estimation of the mean-residence time of atmospheric aerosols could be based on measurements of the activities and ratios of activities of cosmic-ray produced radionuclides, such as (7)Be and the radioactive decay products of radon-222 emanated from soil into the atmosphere, such as (210)Pb, (210)Bi and (210)Po. It was found that a mean value of about 8 days could be applied to aerosol particles in the lower atmosphere below precipitation cloud levels as resulted by the application of two different methods, i.e. the (7)Be-associated atmospheric aerosols and the radon decay product aerosols at two different locations, i.e. at Thessaloniki, Greece 40 degrees 38'N 22 degrees 58'E with dry (precipitation free) climate and at Oak Ridge, Tennessee, USA 35 degrees 58'N 84 degrees 17'W with high precipitation (wet climate), roughly at similar temperate latitudes, but the first one at East longitude and the other at West longitude, respectively.     

Quantification of the dependency of radon emanation power on soil temperature

A study on the quantification of the dependency of the radon emanation power on soil temperature has been made using the accumulation method. The emanation from dry soil was studied at temperatures between −20°C and 45°C. A formula to calculate the radon emanation power as a function of the temperatures has been developed. The formula would contribute to the modeling of radon transport in soils and building materials.     

Assessment of radon-222 concentrations in buildings, building materials, water and soil in Jordan.

Monitoring of radon gas ((222)Rn) in Jordan was started in the early 1990s. Since then our radon group at Yarmouk University and others have carried out tens of studies that include measurements of indoor radon, radon in water, radon in soil and radon emanating from building materials. All major cities of Jordan had been surveyed, from the northern city of Irbid down to the southern port city of Aqaba. Most of these studies were carried out by using time-integrated passive radon dosimeters containing CR-39 solid-state nuclear track detectors. In addition to that, an active radon monitor was used to study the seasonal variation of (222)Rn in Al-Ruseifa that lies near abandoned phosphate mines and in Amman area. During such a study passive dosimeters were also used. The average radon concentrations in dwellings in Jordanian cities ranged from about 20 to 386 Bq/m(3) with the highest readings exhibited during the winter season around the town of Al-Ruseifa.     

Natural radioactivity and radon exhalation rate of soil in southern Egypt

The level of natural radioactivity in soil of 30 mining samples collected from six locations in southern Egypt was measured. Concentrations of radionuclides in samples were determined by γ-ray spectrometer using HPGe detector with a specially designed shield. The obtained results of uranium and thorium series as well as potassium (K-40) are discussed. The present data were compared with data obtained from different areas in Egypt.

Also, a solid state nuclear track detector SSNTD (Cr-39) was used to measure the radon concentration as well as exhalation rate for these samples. The radon concentrations were found to vary from 1.54 to 5.37 Bq/kg. The exhalation rates were found to vary from 338.81 to 1426.47 Bq/m²d. The values of the radon exhalation rate are found to correspond with the uranium concentration values measured by the germanium detector in the corresponding soil samples.     

我国部分地区土壤氡析出率的理论模型

目的 本研究旨在通过理论研究和实验验证初步建立我国部分地区土壤氡析出率的理论模型。方法 通过对氡在土壤中扩散理论的分析，建立土壤氡析出率数学模型，该模型考虑了土壤的镭含量、射气系数、孔隙度和含水饱和度等因素对氡析出率的影响。为验证此模型，我们在北京、贵阳和内蒙古3个不同土壤类型的地区，共30处进行了氡析出率及土壤相关物理性质的实际测量。结果 有近1／3的样品理论值与实测值吻合比较好。结论 实测结果初步显示出模型的有效性。笔者对误差分布规律及产生原因进行了分析，提出了今后土壤氡析出率模型的改进方向。