Analytical solutions of three-dimensional contaminant transport in uniform flow field in porous media: A library

The purpose of this study is to present a library of analytical solutions for the three-dimensional contaminant transport in uniform flow field in porous media with the first-order decay, linear sorption, and zero-order production. The library is constructed using Green’s function method (GFM) in combination with available solutions. The library covers a wide range of solutions for various conditions. The aquifer can be vertically finite, semi-infinitive or infinitive, and laterally semi-infinitive or infinitive. The geometry of the sources can be of point, line, plane or volumetric body; and the source release can be continuous, instantaneous, or by following a given function over time. Dimensionless forms of the solutions are also proposed. A computer code FlowCAS is developed to calculate the solutions. Calculated results demonstrate the correctness of the presented solutions. The library is widely applicable to solve contaminant transport problems of one- or multiple- dimensions in uniform flow fields.     

Transport of volatile compounds in porous media in the presence of a trapped gas phase

The presence of an immobile gaseous phase in an otherwise-saturated porous medium affects the transport of volatile compounds. The linear theory of partitioning tracers suggests that a volatile tracer introduced into such a system should be retarded with a constant retardation factor. Using high concentrations, however, the saturation of the gaseous phase will change as an effect of the tracer test itself. Competitive gas transfer among all volatile compounds and the change of saturation may lead to tracer concentrations that are temporarily higher than those injected. We analyze the system in the framework of the coherence theory by Helfferich [Soc. Pet. Eng. J. 21 (1) (1981) 51]. The governing equations are formulated as functions of total concentration, i.e., the mass of solutes in all phases per pore volume. Neglecting dispersion and mass-transfer kinetics, we derive the characteristic form of the resulting system of hyperbolic equations. In a system with N volatile compounds, a variation of the concentrations splits up into N waves, each traveling with its own characteristic velocity. If the presence of a gaseous phase is sustained, one wave will be a standing one. We perform numerical model calculations for tracers with various Henry's law coefficients and show that the results agree with the semi-analytical solution obtained by coherence theory.     

Non-Fickian dispersion in a single fracture

Solute transport in fractured rocks is of major interest in many applications, from the petroleum industry to ground water management. This work focuses on the dispersion process in a transparent replica of a real single fracture. The fracture exhibits strong changes in heterogeneity, with the first half very heterogeneous and the second half fairly homogeneous. Three models have been used to interpret the tracer experiments: the classical advection-dispersion equation (ADE), the continuous time random walk (CTRW), and the stratified model. The main goals were to test these models and to study possible correlations between fitting parameters and heterogeneities. As expected, the solution derived from the ADE equation appears to be unable to model long-time tailing behavior. On the other hand, the results confirm the CTRW robustness and the coefficient beta seems well correlated to heterogeneities. Finally, the stratified model is also able to describe non-Fickian dispersion. The parameters defined by this model are correlated to the heterogeneities of the fracture.     

The Impact of Global NGOs on Japanese Press Coverage of Climate Negotiations: An Analysis of the New “Background Media Strategy”

This article assesses the success of WWF Japan’s “Background Media Strategy” in influencing Japanese mainstream news outlets’ coverage of climate change negotiations. WWF Japan adopted this “Background Media Strategy” after the Bali COP in 2007; instead of lobbying, it aims to build journalists’ expertise. This article examines its success after seven years through three research approaches: the analysis of participant lists; two surveys (conducted in 2009 and 2015); and a content analysis of climate change articles that appeared in four large mainstream newspapers between April and July 2015. Based on these different data, the author concludes that the new media strategy was successful: Japanese journalists increasingly rely on information provided by WWF Japan and less on information provided by the government and industry. This experiment suggests that a new relationship between global NGOs and the media can improve environmental communications—an approach that could help advocacy groups around the world.     

裂隙地下水中残留LNAPL物理驱替冲洗实验

利用透明复制裂隙模型，选择两种典型LNAPL（轻非水相液体）-邻二甲苯和十二烷残留体，开展一系列水流驱替冲刷和SDS（十二烷基磺酸钠）表面活性剂增强驱替实验，直接获取了裂隙内部LNAPL残留体几何形状与分布情况，结果表明：水流驱替冲刷和SDS驱替裂隙内残留体的去除率分别为8.3%~12.3%和65.9%~82.1%.残留体累积去除率随着驱替流体雷诺数的增加而增加.水流驱替冲刷条件下，残留体离散为小液滴，数量比初始残留状态增加1.3~2.2倍.SDS表面活性剂降低了"LNAPL-水"间的界面张力，能够有效去除裂隙内较大残留体，驱替后仅残余单个面积为1mm²左右的微小液滴.由于粗糙裂隙的非均质性，水流冲刷易导致系统内的"LNAPL-水"有效界面面积增加，对LNAPL污染修复不利，表面活性剂增强修复是一种更有效的方法.     

Fate of pharmaceuticals--photodegradation by simulated solar UV-light

The fate of pharmaceuticals in surface waters under solar irradiation was investigated. Photodegradation of pharmaceuticals caused by sun irradiation may be of major significance in the natural elimination process. Based on a data compilation from the literature, the lipid lowering agent metabolite clofibric acid, the iodinated X-ray contrast media iomeprol, which contribute to the adsorbable organic halogen compounds, and the antiepileptic drug carbamazepine were selected. The irradiation experiments were carried out in batch experiments with simulated UV–sunlight. The photodegradation of the pharmaceuticals showed a pseudo-first-order kinetics. The objective of this investigation was to demonstrate that the extent of photoinduced degradation of pharmaceuticals can vary significantly for the different pharmaceuticals and it strongly depends on the water constituents present in solution. The influences of different initial pharmaceutical concentrations, the presence of other pharmaceuticals like carbamazepine or clofibric acid and the presence of natural organic matter on the photochemical degradation rate of pharmaceuticals in aqueous solutions were investigated. Analyses of the pharmaceuticals and their photodegradation products were carried out by high performance liquid chromatography with diode-array and fluorescence detection.     

生物法净化低浓度苯乙烯有机废气填料的选择及运行功效

采用培养驯化的污泥菌种,对1#陶粒、2#陶粒、塑料小球和沸石4种填料进行生物挂膜,通过对比筛选,选择性能优越的1#陶粒作为滴滤塔填料净化苯乙烯废气,结果表明,在进气量Q=0.6 m3/h,循环喷液量L=90 L/min,进气负荷小于180 g/(m3·h),去除负荷可达到163 g/(m3·h),苯乙烯净化效率达到90%以上.     

含油污水的综合处理法及其应用

概述了竖向隔板分油法、蜂窝斜管分油法及磁性颗粒吸附过滤法 ,将这 3种方法结合处理某机修厂的含油污水 ,取得了满意效果。     

Measurement and analysis of non-Fickian dispersion in heterogeneous porous media

Contaminant breakthrough behavior in a variety of heterogeneous porous media was measured in laboratory experiments, and evaluated in terms of both the classical advection-dispersion equation (ADE) and the continuous time random walk (CTRW) framework. Heterogeneity can give rise to non-Fickian transport patterns, which are distinguished by "anomalous" early arrival and late time tails in breakthrough curves. Experiments were conducted in two mid-scale laboratory flow cells packed with clean, sieved sand of specified grain sizes. Three sets of experiments were performed, using a "homogeneous" packing, a randomly heterogeneous packing using sand of two grain sizes, and an exponentially correlated structure using sand of three grain sizes. Concentrations of sodium chloride tracer were monitored at the inflow reservoir and measured at the outflow reservoir. Breakthrough curves were then analyzed by comparison to fitted solutions from the ADE and CTRW formulations. In all three systems, including the "homogeneous" one, subtle yet measurable differences between Fickian and non-Fickian transport were observed. Quantitative analysis demonstrated that the CTRW theory characterized the full shape of the breakthrough curves far more effectively than the ADE.     

深层过滤理论与技术的研究进展

深层过滤是水处理工艺中的重要单元操作。近年来 ,在滤料、过滤工艺的研究开发及过滤理论研究方面有了新的发展。本文评述了一些主要研究进展