Polychlorierte Dibenzo-p-dioxine, -furane (PCDD/F) und Analoga in Oberflächensedimenten und datierten aquatischen Sedimentkernen

Polychlorinated Dibenzo-p-dioxins, -furans (PCDD/F) and Analogues in Surface Sediments and Dated Aquatic Sediment Cores Aquatic sediments are the final sinks of unintentionally formed PCDD/Fs. Still not known are the conditions of formation of PCDD/Fs in the 8120 years old sediments in Japan and in 350 to 400 years old sediments in the Baltic. Sediments are means of source identification if transformation processes are taken into consideration in view of hydrological conditions. PCDD/Fs have been analysed 30 km from the source in sediments and over a distance of 50 km in benthos indicating a remarkable bioaccumulation potential. Elaborated data of the PCDD/F sediment contamination are missing as well as information on internal diagenetic processes, interactions at the sediment/water interface, and on the aerobic and anaerobic biodegradation and bioavailability of PCDD/Fs in sediments. Quality criteria for sediments and aquatic ecosystems remain to be elaborated.     

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.     

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.     

Some Simple Statistical Models For Relative And Absolute Dispersion

Observations of the dispersion of a contaminant plume in the atmospheric boundary layer, obtained using a Lidar, are analysed in the coordinate frame relative to the instantaneous centre of mass of the plume, as well as the absolute (or fixed) coordinate frame. The study extends the work presented in a previous article, which analysed the structure of the probability density function (pdf) of concentration within the relative coordinate frame. Firstly, the plume displacement component, or plume meander, is analysed and a simple parametric form for the pdf of the plume centreline position is suggested. This is then used to analyse the accuracy and applicability of absolute framework statistical quantities obtained by a convolution of the relative frame statistical quantity with the plume centreline pdf.     

滇东华力西期不整合面含金性

多年对滇东地质勘查和矿业开发研究中发现，区内各金矿床(体)的赋存部位，多沿被动大陆边缘华力西期不整合面分布。由于区内华力西期不整合面明显受到边缘NS两侧两条深大断裂控制，多期NE～SW向左行剪切挤压作用，使不整合面上下地块以其为差异变形轴，旋转产生多期构造剥离或错移，在不整合面上下层位中形成较发育的构造剥离空间、张裂带或板劈理带。这些略呈线型分布的构造挤压带，在地史发展过程中，卷入多期构造变形后演变成局限断裂陷槽或槽沟环境，沉积了一套有别于其它区域的岩性组合。边缘深大断裂多期次海底基性火山喷发或喷流作用。除提供了幔源、壳源含金物质和含矿热液的活化与迁移的通道外，再次卷入构造变形的这些局限断裂陷槽或槽沟又成为区域金成矿物质聚集的有利场所，含矿热液选择沉积其内或堆积其中的细碎屑岩、粘土质岩、含碳质泥质岩类、不纯碳酸盐岩进行交代与沉淀，不受层控的影响，形成了滇东沿华力西期不整合面或接触带金成矿带。     

Similarity Scaling Of Surface-Released Smoke Plumes

Concentration fluctuation data from surface-layer released smokeplumes have been investigated with the purpose of finding suitable scaling parametersfor the corresponding two-particle, relative diffusion process.Dispersion properties have been measured at downwind ranges between 0.1 and 1 km from a continuous, neutrally buoyant ground level source. A combinationof SF₆ and chemical smoke (aerosols) was used as tracer. Instantaneous crosswind concentration profiles of high temporal (up to 55 Hz) and spatialresolution (down to 0.375 m) were obtained from aerosol-backscatter Lidar detectionin combination with simultaneous gas chromatograph (SF₆) reference measurements. The database includes detailed crosswind concentration fluctuation measurements. Each experiment, typically of 1/2-hour duration, containsplume mean and variance concentration profiles, intermittency profiles andexceedence and duration statistics. The diffusion experiments were accompanied by detailed in-situ micrometeorological mean and turbulence measurements. In this paper, a new distance-neighbour function for surface-released smoke plumes is proposed, accompanied by experimental evidence in its support. The new distance-neighbour function is found to scale with the surface-layer friction velocity,and not with the inertial subrange dissipation rate, over the range of distance-neighbour separations considered.     

GC-MS联用技术对卤水中有机物的分析

盐湖卤水由于富集了大量的复杂有机物,而具有浓厚的颜色,脱除这些有色物质,既可以减少卤水对生产设备的危害,又可以提高产品的色度,有利于卤水的综合开发利用,是卤水精制的主要内容。采用不同极性的有机溶剂正己烷和氯仿分别对盐湖卤水中的有机物进行萃取分离,浓缩处理,通过GC-MS联用技术对萃取后的有机提取物进行分离和结构鉴定。结果表明,盐湖卤水中主要含有一些饱和脂肪烃、芳香烃、醇类、酯类、酮类和醚类有机物,为卤水脱色的研究提供了一定的线索和指导。     

First-principles investigation of the concentration effect on equilibrium fractionation of Ca isotopes in forsterite

Previous theoretical studies have found that the concentration variations within a certain range have a prominent effect on inter-mineral equilibrium isotope fractionation(10^3 lna).Based on the density functional theory,we investigated how the average Ca–O bond length and the reduced partition function ratios(10^3 lnb)and103lna of 44 Ca/40 Ca in forsterite(Fo)are affected by its Ca concentration.Our results show that Ca–O bond length in forsterite ranges from 2.327 to 2.267 A with the Ca/(Ca+Mg)varying between a narrow range limited by an upper limit of 1/8 and a lower limit of 1/64.However,outside this narrow range,i.e.,Ca/(Ca+Mg)is lower than1/64 or higher than 1/8,Ca–O bond length becomes insensitive to Ca concentration and maintains to be a constant.Because the 10^3 lnb is negatively correlated with Ca–O bond length,the 10^3lnb significantly increases with decreasing Ca/(Ca+Mg)when 1/64相似文献   

Sorption Preconcentration and Determination of Cobalt in Industrial Solutions by Diffuse Reflection Spectroscopy Method

Cobalt and its compounds have a broad field of application in Russian industries, being essential raw materials for metallurgy, medicine, and agriculture. That is why the production of cobalt is one of the key industries in Russia. Cobalt is produced from mineral raw materials as well as from secondary raw materials (for example, after processing of spent catalysts of oil refinery). It can also be obtained as a by‐product of nickel, manganese, and some other metals processing. That is the reason why the solutions of Ni and Mn industries contain up to 50 g/L of cobalt. obalt compounds are harmful for men’s heart, bloodvessel system, and thyroid gland. This fact explains the importance of the monitoring of cobalt concentrations in natural water and sewages. This task can be effectively achieved using the analytical sorption technique. The present work is focused on the preconcentration of cobalt and its determination by means of diffuse reflection spectroscopy. The preconcentration of cobalt was carried out using the macronetwork cation exchangers KB‐2M and KB‐2‐3T synthesized on the basis of methyl acrylate and long‐chain cross‐linking agents copolymers. Based on these collectors, a cobalt determination method in industrial solutions was worked out using solid‐phase spectroscopy. The colored surface compound to be determined was obtained by a preceding cobalt sorption on the resin and by subsequent treatment of the concentrate obtained with definite amount of nitroso‐R‐salt. The Co calibration curve is linear in the concentration range of 0.05...0.50 mg/L Co (sample volume is 50.0 mL) and the detection limit is 0.02 mg/L (1 μg absolute).     

Extension of a fluctuating plume model of tracer dispersion to a sheared boundary layer and to a large array of obstacles

Fluctuating plume models provide a useful conceptual paradigm in the understanding of plume dispersion in a turbulent flow. In particular, these models have enabled analytical predictions of higher-order concentration moments, and the form of the one-point concentration probability density function (PDF). In this paper, we extend the traditional formalism of these models, grounded in the theory of homogeneous and isotropic turbulent flow, to two cases: namely, a simple sheared boundary layer and a large array of regular obstacles. Some very high-resolution measurements of plume dispersion in a water channel, obtained using laser-induced fluorescence (LIF) line-scan techniques are utilised. These data enable us to extract time series of plume centroid position (plume meander) and dispersion in the relative frame of reference in unprecedented detail. Consequently, experimentally extracted PDFs are able to be directly compared with various theoretical forms proposed in the literature. This includes the PDF of plume centroid motion, the PDF of concentration in the relative frame, and a variety of concentration moments in the absolute and relative frames of reference. The analysis confirms the accuracy of some previously proposed functional forms of model components used in fluctuating plume models, as well as suggesting some new forms necessary to deal with the complex boundary conditions in the spatial domain.