Radon flux density at the Earth’s surface as a possible indicator of the stress and strain state of the geological environment

Usage of the radon flux density at the Earth’s surface as an indicator of seismic activity is proposed in addition to unit-volume radon activity in the soil air that has previously been used for this purpose. Numerical calculations based on the diffusion-convection equation for radon transport in porous media are presented, which confirm that the radon flux density is more sensitive to changes in convection rate than unit-volume radon activity. It has been indicated that the advantage in using radon flux density could be greatest for homogeneous geological media.     

Natural integration of scalar fluxes from complex terrain

Large eddy simulations of turbulent flow and transport in the atmospheric boundary layer were conducted over heterogeneous sources of heat and water vapor to identify the blending properties of the turbulent mixing in an unstably stratified boundary layer. The numerical simulations show that the concept of blending in the ABL is in fact a useful one, even under convective conditions, for a range of surface conditions. Since the transport eddies that are responsible for the blending have sizes that are constrained by the boundary layer depth, and since the vertical motion is so important under the unstable density stratification studied here, we see that when the length scales of the source variability on the land surface become significantly greater than the ABL depth the blending is lost. In this case the source fields remain relatively uncoupled by the important eddy motion. However, for smaller surface length scales, the dynamic eddy motion couples the surface patches. Hence, there is good reason that the land surface exchange phenomenon would not be scale invariant over the entire range of scales. Because of the active role of temperature the effects of inhomogeneous surface sources of sensible heat persist higher into the ABL than do the effects of surface sources from more passive scalars, such as water vapor. Moreover, the mean fields of potential temperature and specific humidity blend at much lower heights than do the vertical turbulent flux fields of these two scalars. We propose a useful measure of blending efficiency for simulation studies and show how this bridges from the dynamics responsible for the blending to the horizontal homogeneity of scalar flux fields at measurement heights in the ABL.     

Radon volumetric activity and ion production in the undisturbed lower atmosphere: Ground-based observations and numerical modeling

The results of in situ ground-based observations of radon volumetric activity carried out at the Borok Geophysical Observatory of Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences (58°04′ N; 38°14′ E) are presented. Modeling the characteristic diurnal variation in the ion production rate in the undisturbed midlatitude lower atmosphere above land is carried out. The Lagrangian stochastic model of turbulent transport is developed in application to determining the vertical profiles of radon activity for 222Rn and 220Rn isotopes and their radioactive decay products. The results calculated by the Lagrangian stochastic model are matched with the analytical solution for the free atmosphere. Based on the model, the estimate is obtained for the rate of radon outflow from the convective boundary layer to the free clear sky atmosphere. The implications of temperature stratification of the atmosphere for the vertical distribution of the ion production rate at the different radon emission rate are explored.     

Radon (222Rn) in ground water of fractured rocks: a diffusion/ion exchange model

Ground waters from fractured igneous and high-grade sialic metamorphic rocks frequently have elevated activity of dissolved radon (222Rn). A chemically based model is proposed whereby radium (226Ra) from the decay of uranium (238U) diffuses through the primary porosity of the rock to the water-transmitting fracture where it is sorbed on weathering products. Sorption of 226Ra on the fracture surface maintains an activity gradient in the rock matrix, ensuring a continuous supply of 226Ra to fracture surfaces. As a result of the relatively long half-life of 226Ra (1601 years), significant activity can accumulate on fracture surfaces. The proximity of this sorbed 226Ra to the active ground water flow system allows its decay progeny 222Rn to enter directly into the water. Laboratory analyses of primary porosity and diffusion coefficients of the rock matrix, radon emanation, and ion exchange at fracture surfaces are consistent with the requirements of a diffusion/ion-exchange model. A dipole-brine injection/withdrawal experiment conducted between bedrock boreholes in the high-grade metamorphic and granite rocks at the Hubbard Brook Experimental Forest, Grafton County, New Hampshire, United States (42 degrees 56'N, 71 degrees 43'W) shows a large activity of 226Ra exchanged from fracture surfaces by a magnesium brine. The 226Ra activity removed by the exchange process is 34 times greater than that of 238U activity. These observations are consistent with the diffusion/ion-exchange model. Elutriate isotopic ratios of 223Ra/226Ra and 238U/226Ra are also consistent with the proposed chemically based diffusion/ion-exchange model.     

Parameter Variations in the Subsoil Radon Field at the Paratunka Station of the Petropavlovsk-Kamchatsky Geodynamic Test Site in 2011–2016

A network of stations for subsoil radon monitoring is in operation at the Petropavlovsk-Kamchatsky geodynamic testing area and is aimed at detection of strong earthquake precursors. At all stations, measurements are carried out using gas-discharge counters located at different depths within aeration zones of soft sediments. The volume activity of radon (VA Rn) is monitored at the most equipped station Paratunka (PRT) at three measurement sites located across the regional fault. The radon flux density (RFD) is measured from the surface. The article reviews responses in the dynamics of VA Rn and RFD from the surface at the PRT station prior to the Kamchatka earthquakes with magnitudes М _W > 5 that occurred over the period of 2011–2016. The revealed RFD seasonal cycle is likely related to the seasonal variations in air temperature. The postseismic effect caused by the strongest deep Okhotsk earthquake (May 24, 2013, М _W = 8.3) is detected in the RFD data. The behavior of VA Rn dynamics during time periods of the strong earthquakes is different. The results confirm the existing opinion on the formation of narrowly localized zones of Rn runoff to the atmosphere owing to both vertical and horizontal irregularities in the top layer of soil, which can react differently to changes in the geoenvironment stress–strain. On the basis of the real-time radon monitoring data, the authors have issued partially successful short-term prediction for several earthquakes. The results of this work confirm the opinion of many researchers that radon monitoring can be used in the short-term prediction of strong earthquakes.     

Radon anomalies and volcanic eruptions

A well-documented case of ²²²Rn anomaly preceding the eruptive activity of Karymsky volcano (Kamchatka) was recently reported in the literature. Stimulated by this example, we have attempted to utilize the available data on radon emanation from rocks, its solubility, and its circulation in waters to discuss how a ²²²Rn anomaly can be produced by magma approaching the surface. It is shown that the most likely process of radon release is the flushing of gases through pore fluids. Heating of extensive fracture surfaces by high-temperature gases may also be important. In order to survive in detectable amounts after moving distances greater than a few meters, radon must be transported by fast-moving fluids, such as those rising toward the surface through a fracture or in the ascending limbs of fluids convecting in very porous rocks under high temperature gradients. The pattern observed at Karymsky volcano is interpreted on the basis of these relations.     

近地层能量闭合度对陆面过程模式影响

大量近地层观测试验表明,利用涡动相关法观测的湍流通量小于近地层可利用能量,即近地层能量是不闭合的,这种不闭合度一般为20%甚至更高.而陆面过程模式是基于地气间能量平衡建立,并且模式中的湍流边界层参数化方案通常根据实际观测的湍流通量来确定,因此能量不闭合必将对陆面过程模式造成一定的影响.本文利用2007年春季SACOL站的近地层观测资料,依据能量守恒将能量不闭合中的残余能量通过波文比分配到观测的湍流通量中,即修正涡动相关法观测的湍流通量使得近地层能量达到平衡;之后分别利用观测和修正的湍流通量,建立了能量不闭合和闭合情形下的湍流参数化方案,借助陆面过程模式SHAW,通过数值模拟和对比分析方法考察近地层能量闭合度对陆面过程模式的影响.研究结果表明近地层能量闭合对陆面过程模式有显著的影响:在陆面过程数值模拟中,当应用近地层能量不闭合的湍流通量形成的湍流参数化方案时,陆面过程模式会明显高估地表长波辐射及土壤温度;但当应用修正湍流通量使得近地层能量达到闭合形成的湍流参数化方案后,在不改变任何地表土壤物理生化属性的情况下,陆面过程模式能较好地模拟地表长波辐射和土壤温度.     

Non-isothermal soil water transport and evaporation

A detailed model was formulated to describe the non-isothermal transport of water in the unsaturated soil zone. The model consists of the coupled equations of mass conservation for the liquid phase, gas phase and water vapor and the energy conservation equation. The water transport mechanisms considered are convection in the liquid phase, and convection, diffusion and dispersion of vapor in the gas phase. The boundary conditions at the soil–atmosphere interface include dynamical mass flux and energy flux that accounts for radiation transport. Comparison of numerical simulations results with published experimental data demonstrated that the present model is able to describe water and energy transport dynamics, including situations of low and moderate soil moisture contents. Analysis of field studies on soil drying suggests that that dispersion flux of the water vapor near the soil surface, which is seldom considered in soil drying models, can make a significant contribution to the total water flux.     

Measurements of radon flux and soil-gas radon concentration along the Main Central Thrust, Garhwal Himalaya, using SRM and RAD7 detectors

Radon in the Earth’s crust or soil matrix is free to move only if its atoms find their way into pores or capillaries of the matrix. ²²²Rn atoms from solid mineral grains get into air, filling pores through emanation process. Then ²²²Rn enters into the atmosphere from air-filled pores by exhalation process. The estimation of radon flux from soil surface is an important parameter for determining the source term for radon concentration modeling. In the present investigation, radon fluxes and soil-gas radon concentration have been measured along and around the Main Central Thrust (MCT) in Uttarkashi district of Garhwal Himalaya, India, by using Scintillation Radon Monitor (SRM) and RAD7 devices, respectively. The soil radon gas concentration measured by RAD7 with soil probe at the constant depth was found to vary from 12 ± 3 to 2330 ± 48 Bq·m^?3 with geometrical mean value of 302 ± 84 Bq·m^?3. Th significance of this work is its usefulness from radiation protection point of view.     

山西夏县中心地震台断层逸出气氡、溶解水氡测值干扰因素分析

山西夏县中心震台断层逸出气氡及溶解水氡分别观测中条山山前断裂土壤逸出气氡及热水井的水中溶解氡值。观测灵敏度高、信息量大,但易受其他因素的干扰。通过对观测值进行分析,发现,夏县台断层逸出气氡测值与气温呈正相关,与气压呈负相关;气温、气压对夏县台热水井溶解水氡测值几乎没有影响,但受水位的影响较明显。     

Radium isotopes in river sediments of Czech Republic

In the Czech Republic, river bottom sediments have been systematically monitored since 1999. In the paper, their radioactive contamination due to uranium mining and milling is assessed. The sediments samples were analyzed by gamma spectrometry. Especially the radium-226 and radium-228 activities were further evaluated.The highest values of the radium-226 activities were found at river profiles where the uranium industry impact was obvious. It turned out that the radium-226 and radium-228 activities ratio is more convenient to assess the level of radium-226 contamination than only the radium-226 activity itself. Based on this hypothesis, the sediment classification scheme for uranium industry contamination was suggested. The natural background activities of radium-226 and radium-228 in the Czech Republic were also evaluated. The case of radium-226 contamination due to the uranium industry was studied in details at the Ploučnice River.     

Indirect air–sea interactions simulated with a coupled turbulence-resolving model

A turbulence-resolving parallelized atmospheric large-eddy simulation model (PALM) has been applied to study turbulent interactions between the humid atmospheric boundary layer (ABL) and the salt water oceanic mixed layer (OML). The most energetic three-dimensional turbulent eddies in the ABL–OML system (convective cells) were explicitly resolved in these simulations. This study considers a case of shear-free convection in the coupled ABL–OML system. The ABL–OML coupling scheme used the turbulent fluxes at the bottom of the ABL as upper boundary conditions for the OML and the sea surface temperature at the top of the OML as lower boundary conditions for the ABL. The analysis of the numerical experiment confirms that the ABL–OML interactions involve both the traditional direct coupling mechanism and much less studied indirect coupling mechanism (Garrett Dyn Atmos Ocean 23:19–34, 1996). The direct coupling refers to a common flux-gradient representation of the air–sea exchange, which is controlled by the temperature difference across the air–water interface. The indirect coupling refers to thermal instability of the Rayleigh–Benard convection, which is controlled by the temperature difference across the entire mixed layer through formation of the large convective eddies or cells. The indirect coupling mechanism in these simulations explained up to 45 % of the ABL–OML co-variability on the turbulent scales. Despite relatively small amplitude of the sea surface temperature fluctuations, persistence of the OML cells organizes the ABL convective cells. Water downdrafts in the OML cells tend to be collocated with air updrafts in the ABL cells. The study concludes that the convective structures in the ABL and the OML are co-organized. The OML convection controls the air–sea turbulent exchange in the quasi-equilibrium convective ABL–OML system.     

The effects of small water bodies on the atmospheric heat and water budgets over the MacKenzie River Basin

The effects of small water bodies or lakes on the surface sensible and latent heat fluxes and the transport of heat and water vapour in the atmospheric boundary layer (ABL) over the Mackenzie River Basin (MRB) are studied from two cases, which occurred on 2 and 8 June 1999 during the warm season. The synoptic condition for the cases is representative of about 33% of the synoptic situation over the MRB. The two events are simulated using the Canadian mesoscale compressible community (MC2) model. A one‐way nesting grid approach is employed with the highest resolution of 100 m over a domain of 100 km². Experiments were conducted with (LAKE) and without (NOLAKE) the presence of small water bodies, whose size distribution is obtained through an inversion algorithm using information of their linear dimension determined from aircraft measurement of surface temperature during MAGS (the Mackenzie GEWEX (Global Energy and Water Cycle Experiment) Study) in 1999. The water bodies are assumed to be distributed randomly in space with a fractional area coverage of 10% over the MRB. The results show that, in the presence of lakes, the domain‐averaged surface sensible heat flux on 2 June 1999 (8 June 1999) decreases by 9·3% (6·6%). The surface latent heat flux is enhanced by 18·2% (81·5%). Low‐level temperature advection and the lake surface temperature affect the air–land/lake temperature contrast, which in turn controls the sensible heat flux. In the absence of lakes the surface wind speed impacts the latent heat flux, but in the presence of lakes the moisture availability and the atmospheric surface layer stability control the latent heat flux. The enhancement is smaller on 2 June 1999 as a result of a stable surface layer caused by the presence of colder lake temperatures. The domain‐averaged apparent heat source and moisture sink due to turbulent transports were also computed. The results show that, when lakes are present, heating and drying occur in the lowest 100 m from the surface. Above 100 m and within the ABL, there was apparent cooling. However, the apparent moistening profiles reveal that lakes tend to moisten the ABL through transfer of moisture from the lowest 50–100 m layer. Copyright © 2004 John Wiley & Sons, Ltd.     

地-空界面上天然中子辐射场的数理模型

本文论述了地－空界面上天然宇宙中子流的来源;将天然中子按能量分为快中子组（En＞01MeV）与慢热中子组,建立了地－空界面上天然快中子流与慢热中子流粒子注量率随空间分布的数理方程.理论与实测结果相互验证表明：（1）地－空界面上天然中子流粒子注量率随距近地表高度的增加而呈指数规律减小;（2）地－空界面上天然中子流粒子注量率随海拨高程增加而呈指数规律增加;（3）地－空界面上上升中子流粒子注量率随地表介质含水率的增加而减少.     

夏垫活动断层土壤氡地球化学特征

夏垫活动断层为首都圈重要的断层之一。本文用土壤中气氡测量法在齐心庄和东柳河屯区段进行了野外现场勘测,揭示了研究区土壤氡的地球化学异常,绘制出研究区的氡浓度等值线图,分析了该区段活动断层的上下盘、空间位置及断层走向,并探讨了研究区断裂带的规模及活动性。综合分析认为,断裂带规模较大和断层活动性较强的齐心庄处的夏垫活动断层应为今后地震监测的重点。     

Indoor Radon Radioactivity at the University of Brunei Darussalam

— Indoor radon radioactivity in the rooms on the ground floor and first floor of the Physics Department, Faculty of Science, Universiti Brunei Darussalam was measured using a system that consists of an air filter pump, ZnS detector, photomultiplier tube and counter. Ground floor rooms' radon radioactivity was found to be about three times higher than that of the first floor. The maximum ground floor indoor radioactivity is only 0.39 Bqm^?3, a value relatively low and safe compared to the mean outdoor radon concentration of 1.41 Bqm^?3 measured (HU and TAN, 2000). The main source of radon emanation originates from the ground soil rather than the building materials.     

Relative importance of advective heat transport and boundary layer decoupling in the melt dynamics of a patchy snow cover

For a patchy snow cover the advective heat transport and the near-surface boundary layer decoupling, which have an opposite effect on sensible heat transport onto the snow surface, are both expected to increase in magnitude. The main aim of this study is to investigate the effects of locally developing atmospheric stratification over a discontinuous snow cover which can result in a decoupling from the warm atmosphere. We are particularly interested in the effect of boundary layer decoupling on the net sensible heat flux into the snow. We therefore applied local eddy flux measurements over snow patches at three different heights above the snow surface. We identified wind velocity, turbulence intensity, fetch distance and topographical curvature as the main factors driving the boundary layer depth and the efficiency of advective heat transport to contribute to snow ablation. The atmospheric decoupling is thus shown to be a key mechanism in snow patch survival.     

藏南羊卓雍错湖面大气湍流特征观测分析

湍流运动是大气边界层的本质特征,是地表与大气之间能量和物质交换的主要方式.本文利用2016和2017年4-10月藏南羊卓雍错湖泊涡动观测资料,分析了湖面大气湍流方差和湍流特征量的统计和变化特征.结果表明：（1）不稳定层结下,三维风速分量和超声虚温、水汽密度、CO₂密度的无量纲标准差随稳定度变化符合Monin-Obukhov相似理论的"1/3"或"-1/3"次幂律,垂直风速的拟合效果最好;稳定层结下,除CO₂密度无量纲标准差与稳定度无明显关系外,其他量基本上满足相似性规律;中性条件下,以上物理量的无量纲标准差分别趋近常数：3.57、3.93、0.77、20.91、6.35和11.96.（2）水平方向平均湍流强度（0.60和0.58）大于垂直方向（0.13）,三维方向湍流强度与平均风速的变化呈显著负相关,相关系数分别为-0.39、-0.42和-0.34.（3）湖面湍流动能随风速呈线性增长,增长率达0.45 m/s;近中性层结时湍流动能最大,层结越稳定或不稳定湍流动能均减小.（4）湖泊下午到傍晚动量输送较强,13：00-22：30时间段平均动量通量达0.091 kg/（m·s²）;热量输送以潜热为主,潜热通量日平均值（77.3 W/m²）是感热通量（14.6 W/m²）的5.3倍,感热和潜热通量日变化峰值分别出现在5：30（22.4 W/m²）和16：00（106.6 W/m²）.     

清水河水氡观测的影响因素分析

2006年8月对清水河水氡进行异常核实发现,排除水点采样系统的变化和仪器标定的原因,2000年以来,该井水氡测值具有比较明显的“夏高冬低”的年变特征。分析认为,清水河水氡2005年8月开始出现的大速率转折下降的原因与采样系统发生了变化和原水口出水量逐步减小有关,是地震异常的可能性不大。     

四川水氡测值突跳异常与地震

在四川开展水氡前兆观测的初期,部分水氡点的水氡测值突跳异常很好地对应了其可预测范围内的中强以上地震。水氡测值突跳异常曾作为松潘—平武和盐源—宁蒗等地震预报的重要依据。但在水氡观测至今的完整时间段内,水氡突跳异常总体表现出对应率低,漏报率高的现象。多次预报攻关研究结果显示,水氡观测的异常表现是多种多样的,水氡测值突跳异常只是其中的表现之一。在今后四川及邻区的中强以上地震预报实践中,水氡测值突跳异常仍可作为地震短临预报的重要参考。