Uncertainty Analysis in Atmospheric Dispersion Modeling

The concentration of a pollutant in the atmosphere is a random variable that cannot be predicted accurately, but can be described using quantities such as ensemble mean, variance, and probability distribution. There is growing recognition that the modeled concentrations of hazardous contaminants in the atmosphere should be described in a probabilistic framework. This paper discusses the various types of uncertainties in atmospheric dispersion models, and reviews sensitivity/uncertainty analysis methods to characterize and/or reduce them. Evaluation and quantification of the range of uncertainties in predictions yield a deeper insight into the capabilities and limitations of atmospheric dispersion models, and increase our confidence in decision-making based on models.     

裂隙土等效连续介质的渗透张量及表征单元体积

裂隙土的渗透特性是裂隙土边坡稳定性分析中重要的参数。文中通过分别考虑随机裂隙网络和土体本身的渗透性,推导裂隙土的渗透系数,并用张量的形式表示渗透系数的各向异性。同时建立了确定裂隙土表征单元体积的准则,为应用等效连续介质模型提供了基础。结果表明裂隙土的渗透系数大于裂隙网络和土体的渗透系数,其渗透方向取决于裂隙网络的渗透方向。算例中裂隙土的表征单元体积大约是裂隙长度平均值的5倍。     

Factors Controlling Total Concentration and Aqueous Speciation of Aluminium in an Acidic Headwater Stream of the Bavarian Forest National Park: a Modelling Approach

The purpose of the present paper is to analyse factors controlling total concentration and aqueous speciation of aluminium in the Große Ohe River, using a thermodynamic equilibrium model and a mixing approach. A model compound for humic substances is derived on the basis of the relation between anion deficit and the organic carbon content in the river as well as literature data. An equilibrium speciation model for aluminium is set up, considering this model compound and relevant inorganic solutes. Although the model cannot be verified directly, its results may be viewed as qualitatively correct. Applying the model to measured stream water samples highlights that aqueous speciation of aluminium is mainly controlled by the pH value and discharge and that free aluminium concentrations reach clearly toxic levels during acidic episodes. Comparing measured concentrations of sulfate and H⁺ and calculated concentrations of Al³⁺ with solubility curves of gibbsite like minerals and jurbanite clearly shows that total aluminium concentrations are not controlled by equilibria with these mineral phases alone. The observed relationship can be better explained from a mixture of two distinct waters, representing lowflow and highflow chemistry, and the resulting equilibrium concentrations. This indicates that total aluminium concentration, in particular during high discharge events, is mainly controlled by the mixture of waters with differing chemistry and flowpaths.     

Simulation of Time Series of Concentration Fluctuations in Atmospheric Dispersion Using a Correlation-distortion Technique

Short-duration fluctuations in the concentration of airborne substances can be important in a variety of atmospheric dispersion problems, especially when assessing the risks posed by harmful materials. This paper discusses a simulation technique for generating individual realisations of fluctuating concentration time series in dispersing plumes based on target probability distributions and spectral functions. The scheme uses a correlation-distortion approach to simulate these time series. Gaussian processes with modified spectral characteristics are generated and then transformed to yield non-Gaussian processes with the desired spectral characteristics. The simulation scheme is initially developed for a single receptor, and is then extended to model pairs of correlated time series at two receptors. In fact, the modelling technique can be generalised to an arbitrary number of receptors and this provides, in principal, an approach that is applicable to a wide class of similar problems (such as the modelling of instantaneous puff releases or the response of line-of-sight detection systems). The simulation technique is illustrated using observations made during recent field experiments, conducted both in the United Kingdom and in the U.S.A., investigating the short-range dispersion of a passive tracer.     

中国主要河流控制站氮、磷含量变化规律初探

根据黄河洛口站,长江武汉站和珠江高要站１９８０到１９８９年的水文,水化学资料,分别计算中国３条主要河流下游控制站８０年代营养元素氮,磷平均含量,比较氮,磷含量的季节变化规律,并探讨影响它们含量变化的主要因素。     

吉林省夹皮沟—金城洞绿岩区中金矿床形成的物理化学条件

作者应用气液包裹体研究和热力学方法讨论了吉林省夹皮沟—金城洞绿岩区中金矿床形成的物理化学条件,分别确定了Ⅰ矿田(石(?)沟旷田)、Ⅱ矿田(夹皮沟矿田)和Ⅲ矿田(金城洞矿田)的成矿T、P、pH、Eh、fs_2、fo_2、fco_2及成矿溶液性质、成分类型、主要成矿离子Pb~(2+)、Zn~(2+)、Fe~(2+)、[AuS_3]~(3-)的浓度。     

Farmer Income Differential in Regions

1 Introduction China’s success in reform and opening up policy for twenty years is regarded as China’s miracles in the world, whereas the income differential widening phenomenon has been the focus of the policymakers and researchers. The typical research of personal income allocation in regions on microeconomic data has been done in China Social Science Research Institution, and by the special income allocation research team’s household investiga- tion, we could get the useful farmer’s i…     

Transformation of debris flows into turbidity currents: mechanisms inferred from laboratory experiments

Three sets of lock exchange experiments were run to look at the generation of turbidity currents from debris flows. The flows ranged from reasonably dilute (4% volumetric concentration) to dense (40% volumetric concentration) with cohesive, non-cohesive and mixed cohesive/non-cohesive sediment. Concentration was measured at one height using an Ultrasonic High Concentration Meter. Velocity was measured using Ultrasonic Doppler Velocimetry Profiling at 10 different heights in each run. The resulting flows range from plug flows to well mixed flows. Comparison of the concentration profiles, velocity time–height plots and vertical profiles of downstream velocity and root mean square velocity showed several different transformation mechanisms. Depending on the concentration and composition of the flow, transformation took place through one or more of the following processes: erosion of material from the dense mass, breaking apart of the dense underflow, breaking of internal waves and turbulent mixing. The extent of transformation depends on the viscosity and density of the flow. Initially very dense and viscous flows experience minor transformation only at the surface, resulting in a dilute turbidity current. Flows that are initially not so dense and viscous are churned up entirely, undergoing the different transformation processes. For these flows, transformation processes work throughout the entire flow, not just at the surface. Transformation of the less-dense flows is efficient with all or most material ending up in the resulting turbidity current.     

137Cs and 210Po in Pacific walrus and bearded seal from St. Lawrence Island, Alaska

The activity concentration of Cesium-137 ((137)Cs) and naturally-occurring Polonium-210 ((210)Po) were measured in the muscle tissue, kidney and liver of Pacific walrus (Odobenus rosmarus divergens) and bearded seal (Erignathus barbatus) collected by native hunters from the Bering Sea during May 1996. The mean (137)Cs concentrations in muscle, liver and kidney of Pacific walrus were 0.07, 0.09 and 0.07 Bq kg(-1) (n=5, wet weight), respectively, and 0.17, 0.10, and 0.17 Bq kg(-1) (n=2, wet weight), respectively, in bearded seal. In general, (137)Cs tissue concentrations are significantly lower than those previously reported for mammals from other regions. By comparison, (210)Po activity concentrations are more variable and appear to be higher level compared with mammal data from other regions. The mean (210)Po concentration in the muscle tissue, liver and kidney of Pacific walrus (n=5, wet weight) were 28.7, 189, and 174 Bq kg(-1), respectively. This compares with (210)Po concentration values (n=2, wet weight) of 27, 207 and 68 Bq kg(-1) measured in the muscle tissue, liver and kidney, of bearded seal, respectively. Estimated concentration factors--as defined by the radionuclide concentration ratio between the target tissue to that in sea water--were two to three orders of magnitude higher for (210)Po that those of (137)Cs. We conclude from radiological dose estimates that ingestion of (137)Cs in foods derived from walrus and seal will pose no threat to human health. This work has important implications for assessment of risks of Alaskan coastal communities concerned about the dumping of nuclear waste in the Russia Arctic.     

黑碳气溶胶研究进展Ⅰ：排放、清除和浓度

黑碳气溶胶是近几年非常活跃的一个研究课题，因为黑碳气溶胶吸收太阳和地球大气的辐射，对全球气候变暖有重要的影响。中国黑碳气溶胶的排放和浓度比同纬度的高，在全球气候变暖的大背景下，中国黑碳气溶胶一直受到国外的关注。综述了国内外黑碳气溶胶研究的最新进展，受篇幅的限制，文章分两篇，第一篇是黑碳气溶胶的排放、清除和浓度，第二篇是黑碳气溶胶的气候效应和拓展的研究领域。从黑碳排放的估算和大气浓度的测量方法进行描述，列出有关的测量结果，对黑碳气溶胶的排放和大气浓度进行国内外的初步比较分析。还对黑碳气溶胶排放和浓度测量误差进行了讨论，并对今后黑碳气溶胶研究提出了几点建议。