The physical basis of the effects caused by electromagnetic forcing in the intensity of geoacoustic processes

The results of theoretical and experimental investigations into the physical causes and mechanisms of the electromagnetic effects that modulate the intensity of the geoacoustic processes are presented. The peculiarities of this effect before strong nearby earthquakes are studied.     

Modeling microbial transport in porous media: Traditional approaches and recent developments

A substantial research effort has been aimed at elucidating the role of various physical, chemical and biological factors on microbial transport and removal in natural subsurface environments. The major motivation of such studies is an enhanced mechanistic understanding of these processes for development of improved mathematical models of microbial transport and fate. In this review, traditional modeling approaches used to predict the migration and removal of microorganisms (e.g., viruses, bacteria, and protozoa) in saturated porous media are systematically evaluated. A number of these methods have inherent weaknesses or inconsistencies which are often overlooked or misunderstood in actual application. Some limitations of modeling methods reviewed here include the inappropriate use of the equilibrium adsorption approach, the observed breakdown of classical filtration theory, the inability of existing theories to predict microbial attachment rates, and omission of physical straining and microbe detachment. These and other issues are considered with an emphasis on current research developments. Finally, recently proposed improvements to the most commonly used filtration model are discussed, with particular consideration of straining and microbe motility.     

Vegetation and hydraulic-morphological interactions at the individual plant, patch and channel scale

Interactions between vegetation, flow and sediment are a key ingredient for the development of vegetated islands in highly dynamic, fluvial alpine ecosystems such as the Tagliamento River, north-east Italy. There has been substantial research on factors influencing the establishment of vegetation and feedback mechanisms between vegetation, hydraulic, and geomorphological processes in such environments. This has yielded the development of conceptual models identifying different trajectories of vegetation and landform development from bare gravel to established floodplain forest. Nevertheless, some of the finer-scale processes underpinning such interactions are not well understood and parameterisation concepts that augment our knowledge from process understanding to quantified data and prediction models are not available until now. This paper identifies mechanisms and parameters of vegetation-flow interaction at the individual scale that are reflected at a patch or even at the channel scale. These mechanisms are reviewed from a multi-disciplinary perspective and concepts and analogies are proposed that provide ideas to progress research towards the development of predictive vegetation-flow models. Such models must incorporate both hydraulic and ecological components and this is demonstrated for a simplified force-bending model of Salicaceae seedlings. The development of such models demands advances in the individual disciplines of hydraulics, morphology, plant ecology and biomechanics, which offers many possibilities for multidisciplinary research between these disciplines.     

Recent Progress on Biosorption of Heavy Metals from Liquids Using Low Cost Biosorbents: Characterization,Biosorption Parameters and Mechanism Studies

A significant number of biosorption studies on the removal of heavy metal from aqueous solutions have been conducted worldwide. Nearly all of them have been directed towards optimizing biosorption parameters to obtain the highest removal efficiency while the rest of them are concerned with the biosorption mechanism. Combinations of FTIR, SEM‐EDX, TEM as well as classical methods such as titrations are extremely useful in determining the main processes on the surfaces of biosorbents. Diverse functional groups represented by carboxyl, hydroxyl, sulfate and amino groups play significant roles in the biosorption process. Solution pH normally has a large impact on biosorption performance. In brief, ion exchange and complexation can be pointed out as the most prevalent mechanisms for the biosorption of most heavy metals.     

A coupled physical-biochemical lake model for forecasting water quality

A new one-dimensional numerical model that includes physical and biochemical processes has been developed. The biochemical processes, influenced by the lake dynamics, are required for forecasting water quality. The model is used to investigate the effects of different internal restoration measures, such as artificial mixing, input of oxygen and drainage of deep water.The model is applied to the Northern Basin of Lake Lugano, a Swiss-Italian border lake. The lake is highly eutrophic and chemically stratified throughout the year. The model was calibrated over one year and validated over a period of several years. The results agree well with the measured data. The coupled model reproduces the observed depth dependency of conductivity even during long simulation times. Due to the predominant mixing, decoupled physical models cannot maintain such gradients. The forecasting capabilities of the model are demonstrated for different case studies. The impact of restoration measures on water quality is rather small. Best results are achieved by reducing the external nutrient loading. Caution is recommended for internal measures as these have to be studied in greater detail.     

Atmospheric Electrification in the Solar System

Atmospheric electrification is not a purely terrestrial phenomenon: all Solar System planetary atmospheres become slightly electrified by cosmic ray ionisation. There is evidence for lightning on Jupiter, Saturn, Uranus and Neptune, and it is possible on Mars, Venus and Titan. Controversy surrounds the role of atmospheric electricity in physical climate processes on Earth; here, a comparative approach is employed to review the role of electrification in the atmospheres of other planets and their moons. This paper reviews the theory, and, where available, measurements, of planetary atmospheric electricity which is taken to include ion production and ion–aerosol interactions. The conditions necessary for a planetary atmospheric electric circuit similar to Earth’s, and the likelihood of meeting these conditions in other planetary atmospheres, are briefly discussed. Atmospheric electrification could be important throughout the solar system, particularly at the outer planets which receive little solar radiation, increasing the relative significance of electrical forces. Nucleation onto atmospheric ions has been predicted to affect the evolution and lifetime of haze layers on Titan, Neptune and Triton. Atmospheric electrical processes on Titan, before the arrival of the Huygens probe, are summarised. For planets closer to Earth, heating from solar radiation dominates atmospheric circulations. However, Mars may have a global circuit analogous to the terrestrial model, but based on electrical discharges from dust storms. There is an increasing need for direct measurements of planetary atmospheric electrification, in particular on Mars, to assess the risk for future unmanned and manned missions. Theoretical understanding could be increased by cross-disciplinary work to modify and update models and parameterisations initially developed for a specific atmosphere, to make them more broadly applicable to other planetary atmospheres.     

Removal of Elongated Particle Aggregates on Fibrous Filters

Elongated aerosol particle removal on fibrous filters has been investigated. It was shown that particle agglomerates are removed much more efficiently compared to the regularly shaped single particles with identical electrical mobility diameter at two filtration velocities tested. The experimental results were compared with the classical filtration theory and it was shown that the theoretical predictions, which are based on the assumption that the particles are spherical, are significantly different compared to an agglomerate filtration efficiency value. In order to account for a particle shape non-regularity, dominating nanoparticle removal mechanisms were firstly evaluated for a regular particle of certain size and then adjusted by fitting coefficients k₁ (for diffusion component) and k₂ (for interception). These coefficients were determined by fitting the theoretical values that gives the best coincidence with the measured data points. As was further demonstrated theoretically, the coefficient k₁ is identical to the ratio of the actual particle surface area to the surface area of the spherical particle of the equivalent diameter. On the other hand, the coefficient k₂ was found to be equal to the ratio of the projection of a given particle on a plane perpendicular to a streamline, to that of the spherical particle of the equivalent diameter. The reported findings would allow undertaking more accurate evaluation of the removal efficiency of non-regular aerosol particle, which is especially important for industrial applications where non-regular aerosols are frequently met.     

珠江三角洲对流层气溶胶时空变化特征分析

利用AERONET资料对珠三角地区气溶胶物理性质特征进行分析,建立珠三角地区的气溶胶模型,在此基础上,根据RT3 辐射传输模型构建矢量查找表,采用多角度偏振方法从PARASOL L1B数据反演得到细模态气溶胶光学厚度(AOD),最后采用2007-2009年MODIS总的AOD产品和本文的细模态AOD三年的反演结果分析了珠三角地区气溶胶的时间变化和空间分布特征,为深入研究珠三角地区污染物的局地排放和输送提供了条件.结果表明:(1)珠三角地区对流层气溶胶呈双峰型对数正态分布,其中细粒子平均半径主要集中在0.05~0.1,标准方差以0.5、0.6为主,粗粒子平均半径以0.9、1.0为主,标准方差为0.6、0.7,复折射指数实部以1.4、1.5 居多,虚部以0、0.01为主,细粒子所占比例大于70%,珠三角气溶胶呈现出粗颗粒物和细颗粒物并存的特征;(2)PARASOL业务算法中的气溶胶模型在珠三角地区有较大的局限性,引入当地气溶胶模型使细模态AOD的反演精度较卫星产品有了很大提高,细模态AOD主要反映了珠三角地区二次污染的强度;(3)珠三角地区总AOD值春季较大,秋夏季次之,冬季较小,并呈现逐年较小的趋势;(4)珠三角地区细模态AOD也在逐年降低,2009年细模态AOD年均值比2007年低了0.02,在空间分布上,高值地区主要集中在广州、佛山、中山等城市.     

Possible influence of polymorphic transitions in minerals (according to the quartz example) on seismotectonic processes in the lithosphere

The thermally activated physical processes essential for earthquake source physics and the formation of mylonite layers and deep shear zones are examined. The possibility of the influence of polymorphic (structural) phase transitions in the rock-forming minerals on the geodynamic effects is discussed. On the basis of experimental data, the deformation-strength and elastic properties of stratum containing quartz in the region of the α-β transition in quartz are studied as an example. It is shown that the α-β transition in quartz corresponds in a number of ways to the observed features specific to the physical properties of substance in connection with seismic processes.     

Modeling of nonstationary electron precipitation by the whistler cyclotron instability

We study a simple self-consistent model of a whistler cyclotron maser derived from the full set of quasi-linear equations. We employ numerical calculations to demonstrate dependencies of pulsation regimes of whistler-mode wave interactions with energetic electrons on plasma parameters. Possible temporal evolution of those regimes in real conditions is discussed; calculations are compared with case-study experimental data on energetic electron precipitation pulsations. A reasonable agreement of the model results and the observations has been found.     

Dynamic characteristics of spring sandstorms in 2000

Systematical analyses of spring sandstorms in 2000 affecting Beijing area are carried out. Results revealed the key dynamic mechanisms of dust storm during its mobilization, lifting, horizontal advection and deposition processes. It turns out that in the processes of sandstorms influencing Beijing area in March–April 2000, the dynamic conditions for dust mobilization are significantly correlated with phenomena, such as cold air-related climatic activities, clay soils area of North China and surface friction velocity anomaly. The characteristics of sandstorm can be described by composite mode of dust particles mobilization-lifting-long-range transport. This paper will provide scientific evidences for further studies, prediction and harness of sandstorms in China.     

Modelling the fate of oxidisable organic contaminants in groundwater

Subsurface contamination by organic chemicals is a pervasive environmental problem, susceptible to remediation by natural or enhanced attenuation approaches or more highly engineered methods such as pump-and-treat, amongst others. Such remediation approaches, along with risk assessment or the pressing need to address complex scientific questions, have driven the development of integrated modelling tools that incorporate physical, biological and geochemical processes.We provide a comprehensive modelling framework, including geochemical reactions and interphase mass transfer processes such as sorption/desorption, non-aqueous phase liquid dissolution and mineral precipitatation/dissolution, all of which can be in equilibrium or kinetically controlled. This framework is used to simulate microbially mediated transformation/degradation processes and the attendant microbial population growth and decay. Solution algorithms, particularly the split-operator (SO) approach, are described, along with a brief résumé of numerical solution methods. Some of the available numerical models are described, mainly those constructed using available flow, transport and geochemical reaction packages. The general modelling framework is illustrated by pertinent examples, showing the degradation of dissolved organics by microbial activity limited by the availability of nutrients or electron acceptors (i.e., changing redox states), as well as concomitant secondary reactions. Two field-scale modelling examples are discussed, the Vejen landfill (Denmark) and an example where metal contamination is remediated by redox changes wrought by injection of a dissolved organic compound. A summary is provided of current and likely future challenges to modelling of oxidisable organics in the subsurface.     

松散承压含水层水位的同震响应实验与数值模拟

为深入理解井水位同震响应机理,本文开展了向完整井-松散含水层系统输入由不同频率和振幅（加速度）组成的正弦波荷载的振动台实验。以实验模型为物理模型,建立了振动作用下松散承压含水层中孔隙水压力响应的流固耦合模型和含水层水流与井流的相互作用模型,并运用多物理场耦合模拟软件COMSOL Multiphysics对实验过程进行了数值模拟。实验中观测到的四种典型水位变化形态与野外场地同震井水位变化形态相似。数值模拟结果显示,本研究建立的数学模型能较好地反映松散承压含水层中孔隙水压力和水位的响应情况。本文研究对解释地下水同震响应机制、岩体渗流稳定性和安全问题具有重要意义。     

Effect of sediment particles on the velocity profile of sediment-water mixtures in open-channel flow

The presence of sediment particles in open-channel flow has an important effect on turbulence; thus, an empirical, turbulent eddy viscosity formula was established for application in the limit for low concentrations. The current study establishes a theoretical relation for the mixture viscosity based on the two-phase mixture model. The percentage contribution of the three mechanisms of mixture viscosity,namely, fluid turbulence(FT), particle turbulence(PT), and inter-particle collisions(IPCs), w...     

Identification of potential driving mechanisms for HM coupled time-dependent deformation of argillaceous rocks

With respect to radioactive waste confinement indurated clays are potential host rocks as well as barrier rock formations. Regarding the tight coupling between fluid flow processes and time-dependent deformation in argillaceous rock mass this paper presents recent experimental findings obtained in the Mont Terri URL which are interpreted in terms of potential driving mechanisms for the time-dependent deformation behaviour of the rock. Within the interpretation process, numerical modelling work, reflecting the actual properties of the rock in situ, is performed and the simulation results are compared to the experimental results. The discussion also touches on the work which is in progress on validating the Finite Element Code for physical modelling and numerical simulation (CODE_BRIGHT).     

An application of Mie's series to soft particles

Summary The scattering of electromagnetic radiation from soft particles has been studied by a new method which allows to transform the Mie series into a simplified form through the use of some auxiliary expansions derived in the Appendix of this article. This simplified form (eq. 1) converts into the Hulst and Rayleigh-Debye-Gans' formulae if the parameters of eq. I are properly restricted. A further simplified form (eq. II), improves the well-known Hulst approximation.     

History of forest hydrology

Hydrology as a science and a technology is examined, as are some of the myths on the role of forests in hydrology and water resources. The history of catchment area research is traced, in Europe, in the USA and in East Africa, with particular reference to forest hydrology and, in the earlier years, to water quantity rather than water quality. The importance of associating physical process studies with hydrological systems' investigations, to enhance understanding of why particular catchments behave as they do, is stressed. Recent advances in hydrochemistry have been exploited to elucidate water flow paths within experimental catchments. Stimulated by requirements for research into acidification of surface waters, research catchments have proved to be valuable outdoor laboratories from which a much improved understanding of the flow processes has been achieved. Conflicting claims about the impacts of forestry are described and discussed.     

岩体失稳过程中的振荡现象及断层的多向错动形迹

对三轴实验中岩石突发式破坏和粘滑失稳的瞬时动态过程的研究表明,应力下降和位移增加都不是单一的,而是一种含有多种频率成分的振荡过程。用扫描电镜对错动面的观察表明,这种振荡导致双向或多向错动形迹的发育。结合天然断层面上常见的双向或多向错动的擦痕、阶步等形迹,以及断层带的异常构造,如反错列等,提出一次断层活动中失稳振荡——地震可能是这些特征的形成原因之一。反之,它们也有可能成为地震的一种标志