Experimental study of migration of potassium ion through a two-layer soil system

A barrier system based on the hydraulic trap design concept for a landfill was proposed. To study the field scenario in which a clay liner is underlain by a granular layer functioning as a secondary leachate drain layer, a laboratory advection–diffusion test was performed to investigate factors controlling the transport of contaminants in a two-layer soil system. The soils used for this study were Ariake clay and, the underlying layer, Shirasu soil from the Kyushu region of Japan. Potassium (K⁺) was selected as the target chemical species with an initial concentration of 905 mg L⁻¹. The effective diffusion coefficients (D _e) of K⁺ for Ariake clay and Shirasu soil were back-calculated using an available computer program, Pollute V 6.3. Values of D _e derived from this experiment are consistent with previously published ones. The Ariake clay has lower D _e than the Shirasu soil. The hypothesis that mechanical dispersion can be considered negligible is reasonable based on both the observation that the predicted values well fit the experimental data and the analyses of two dimensionless parameters. Parametric analyses show that transport of K⁺ through soils is controlled by advection–diffusion rather than diffusion only, whereas at low Darcy velocity (i.e., ≤10⁻⁹ m s⁻¹), transport of K⁺ will be controlled by diffusion. Applications of the test results and parametric analysis results in practical situations were reviewed.     

A study on contaminant migration of sugarcane effluent through porous soil medium

A significantly large volume of effluent is generated during the manufacture of sugar and contains high amount of pollution load. The effluent from sugarcane industry is disposed off on land moves into the wider environment through a number of routes and the soil itself retains the various contaminants in the effluent to a greater or lesser extent depending on the physical nature of the soil. The analysis of contaminant transport through soil used to design of industrial wastewater treatments and disposal systems. This paper discussed the adsorption and diffusion of cations calcium, magnesium, sodium and anions chloride and sulphate by the sorption diffusion permeameter under different hydraulic retentions time of 3 min, 13 min, 27 min and 58 min with a constant diffusion flow rate of 3.6 L/h. In this study, less percentage error found between observed adsorption and diffusion coefficients from the experiments at different hydraulic retentions time and optimum adsorption and diffusion coefficients from the experiments at optimum hydraulic retentions time of 30 min for calcium, magnesium, sodium, choloride and sulphate. The results of regression analysis implied that the adsorption and diffusion coefficients obtained from the equation for cations and anions were good recognizing with the experimental results.     

变荷载下基于指数渗流双层地基一维固结分析

在土中渗流服从指数形式的前提下,建立了变荷载作用下双层地基的一维固结控制微分方程。利用有限差分法求得孔隙水压力的数值解,并通过与解析解对比对其可靠性进行了验证。对双层地基在指数形式渗流时不同参数下的固结性状进行分析,结果表明：单面排水条件下,双层地基中上层土渗流指数的大小对固结速率起决定性作用,而下层土渗流指数大小对固结速率的影响很小;如果上、下两层土体的压缩性不同,则地基按变形定义的平均固结度和按孔压定义的平均固结度不再相等;地基中下层土与上层土的相对压缩性越低、相对渗透性越高,则地基的固结速率越快;增大压缩性小、渗透性高的土层相对厚度,会加快双层地基的固结速率。     

非平衡-非线性吸附情况下填埋场污染物运移分析

采用Langmuir等温吸附线方程描述非线性吸附性能, 基于改进的混合元方法，通过数值计算与分析，探讨了非平衡吸附条件下污染物运移过程及其机理。计算结果表明: 当考虑非平衡、非线性吸附性能时, 污染物穿透曲线即浓度的时程变化曲线尖锐而狭窄、峰值点前移, “拖长尾”现象不明显, 由此说明，土颗粒对污染物的非平衡、非线性吸附使得污染物的穿透能力增强, 滞留能力下降。进一步的变动参数比较分析表明：Langmuir等温线方程中的参数B、压实粘土衬里的渗透性及地下水渗流速度对污染物运移过程具有显著的影响。     

CCL吸附特性及孔隙率降低对污染物运移的影响

假定孔隙均匀地分布于土体的物质空间内和土骨架对污染物的吸附特性服从平衡线性,对基本体积质量关系进行分析,提出了由于土体对污染物的吸附而引起的孔隙率降低的估算公式。在考虑土体孔隙率变化的条件下,建立了污染物一维运移的控制方程,并考虑垃圾生物降解效应、压实黏土衬里（CCL）防渗层、下覆有限厚度含水层等实际情况,确定了初始条件和边界条件。对所建立的初边值问题进行了数值求解,且对某假想填埋场情况进行了变动参数与对比计算,结果表明,由于土颗粒对污染物的吸附所引起的孔隙率降低,显著地降低了污染物对压实黏土衬里的穿透能力。与常孔隙率情况相比,CCL中污染物的峰值浓度降低近10 %,含水层中污染物浓度降低更显著。当考虑土体孔隙率变化时,弥散对污染物运移具有控制作用,分布系数对污染物的运移具有重要影响。     

应用CT扫描研究非饱和砂土中污染物的迁移规律

应用CT扫描技术对两种稳定非饱和状态的砂土试样分层进行扫描,得到不同深度CT扫描层图像,采用Image J图像处理软件将CT图像转化为CT数均值,然后在稳定非饱和试样中分别间断性连续注入污染物KI溶液,测定不同时间间隔CT扫描图像,计算注入污染物先后扫描图像结果的差值,建立CT数均值和污染物迁移之间的关系,研究污染物在非饱和砂土中的运移特征,得出非饱和砂土中污染物浓度随时间和深度的变化规律,对研究其他介质中污染物的迁移具有重要的指导作用。     

Finite-element analysis of time-dependent large-deformation problems

An updated Lagrangian finite-element formulation has been developed for time-dependent problems of soil consolidation involving finite deformations. Large plastic strains as well as rotations occur in such problems and nominal stress measures are introduced in the formulation to redefine stresses. This leads to corrective terms for equilibrium and yield violations in addition to geometric stiffening terms in the governing integral equations. The soil is considered to be either a linear elastic or an elastoplastic, critical-state material. Some simple numerical examples are studied to validate the formulation, followed by a detailed analysis of the problem of penetration of a pile into soil. The results of this problem are viewed with emphasis on the physical interpretation and practical significance.     

Non‐linear consolidation analysis of soil with variable compressibility and permeability under cyclic loadings

In this paper, a simple semi‐analytical method has been developed to solve the one‐dimensional non‐linear consolidation problems by considering the changes of compressibility and permeability of the soil layer, subjected to complicated time‐dependent cyclic loadings at the ground surface. The solution presented here takes into account e ～ lg k_v and e ～ lg σ′ linear responses. With c_k the slope of the e ～ lg k_v line and c_c as the slope of the e ～ lg σ′ line, the identified parameter c_c/c_k is found to control the rate of consolidation. Using the solutions obtained, some diagrams are prepared and the relevant behaviours of one‐dimensional non‐linear consolidation of saturated soft soil under cyclic loadings are discussed. The method in this paper does not require any special data; conventional oedometer data can be used. Therefore, the method is particularly efficient and convenient for engineering practice. Copyright © 2006 John Wiley & Sons, Ltd.     

Integration of creep into a modified hardening soil model for time-dependent analysis of a high rockfill dam

This paper proposes an approach to extend a modified hardening soil model into the time-dependent analysis of high rockfill dams. The key feature of the extended model is the integration of a creep model and the double yield surface elasto-plastic model, via modifying the hardening functions. The integrated model is validated by a laboratory multistage creep test. Results from three-dimensional analyses including the without creep and with creep considerations of the Nam Ngum 2 dam have been compared with the in-situ measurements. The prediction of dam deformation can be significantly enhanced by the proposed model.     

包气带土壤组成对三氯乙烯的吸附影响研究

有机质和矿物质是包气带土壤中的主要吸附介质,其吸附特性直接影响有机污染物在环境中的迁移、转化等过程。分别采用分析纯石英砂和典型粘土矿物高岭石模拟土壤的原生矿物和粘土矿物,利用批实验的方法研究土壤中各组成部分对三氯乙烯(TCE)的吸附行为。土壤有机质的吸附行为通过全土样和矿物质的对比得出。结果表明,粘土矿物是吸附氯代烃的主要矿物质,原生矿物对氯代烃的吸附量很小;土壤有机质含量和土壤吸附量之间有很好的正相关性;土壤有机碳含量与土壤粘土矿物含量的比值是影响吸附行为的另一重要因素,比值越小,Koc值越大,土壤对TCE的亲和力就越强。由于自然界中的土壤有机质大都与矿物质形成有机质-粘土矿物结合体,据此推测有机质-矿物质结合体会影响有机质的组成和形态,从而对其吸附行为有重要作用。     

水—气二相流及污染物运移数值模拟研究

本文通过对近些年来水－气二相流数值模拟进展情况的分析,总结了在水－气二相流模拟过程中,各个主要参数或物理过程的数学概化方法,以及近年来在求解水气二相流方程和污染运移方程的方法上的改进情况。并在此基础上提出了需进一步研究解决的问题。     

Inorganic arsenic sorption by drinking-water treatment residual-amended sandy soil: effect of soil solution chemistry

Previous studies in our laboratory have demonstrated that drinking-water treatment residuals are effective sorbents of arsenic V. However, the effect of soil solution chemistry on arsenic V sorption by drinking-water treatment residuals-amended soils remains to be explored. The current study uses a batch incubation experimental set up to evaluate the effect of soil solution pH, competing ligands, and complexing metal on arsenic V sorption by a sandy soil (Immokalee series) amended with two rates (25 and 50 g kg^?1) of aluminum and iron-based drinking-water treatment residuals. Experiments were conducted at three initial arsenic loads (125, 1,875, 3,750 mg kg^?1) and a constant solid: solution ratio of 200 g L^?1. An optimum equilibration time of 8 days, obtained from kinetic studies, was utilized for sorption experiments with both aluminum and iron drinking-water treatment residual-amended soil. Presence of phosphate decreased arsenic V sorption by both aluminum and iron drinking-water treatment residual amended soils, with a strong dependence on pH, drinking-water treatment residual types, drinking-water treatment residual application rates, and phosphate concentrations. Addition of sulfate had no effect on arsenic V sorption by aluminum or iron drinking-water treatment residual-amended soil. A complementing effect of calcium on arsenic V sorption was observed at higher pH. Results elucidating the effect of soil solution chemistry on the arsenic V sorption will be helpful in calibrating drinking-water treatment residual as a sorbent for remediation of arsenic-contaminated soils.     

The analysis of oil trapped during secondary migration

During secondary migration, there is an opportunity for oil to be trapped as fluid inclusions (FIs) within framework grains such as quartz and within diagenetic cements that have a crystalline structure. Oil saturation on migration pathways remains relatively low, so typically fewer oil inclusions get trapped compared with samples from an oil column. Geochemical analysis of the much smaller amounts of inclusion oil present in samples from interpreted oil migration pathways has been attempted for two samples from the Champagny-1 and Delamere-1 wells in the Vulcan Sub-Basin, northern offshore Australia. A combination of petrographic analysis, bulk geochemical inclusion analysis and log evaluation confirmed that both samples were from oil migration pathways. Despite the small number of oil inclusions, reliable geochemical data were acquired from both samples that were significantly above the levels detected for the system and outside-rinse blanks. The FI oil trapped on the interpreted oil migration pathway in Champagny-1 was generated from clay-rich marine source rock with little terrigenous organic matter input. It was generated at peak oil window maturity and correlates best with oils derived from the Late Jurassic Lower Vulcan Formation. In contrast, the Delamere-1 FI oil contains evidence of greater input of terrigenous organic matter and was generated at early oil window maturity. This FI oil also contains a signature of a biodegraded component, which could have been generated either from the Middle Jurassic Plover Formation, or from an older source rock. These data indicate that it is feasible to geochemically map migration pathways across prospects or basins, and to analyse palaeo-oil compositions in oil zones where the few inclusions get trapped. This also suggests that the few oil inclusions that sometimes occur in Proterozoic or Archaean rocks may be analysable in the future, which would provide relatively pristine and robust data on the composition and diversity of Earth’s early biosphere.     

Unbiased identification of nonlinear sorption characteristics by soil column breakthrough experiments

Accurate identification of interactions of reactive solutes with porous media constituents is necessary for reliable risk assessment studies and the development of efficient sanitation strategies. Standard parameter estimation procedures bear a number of unsolved problems with respect to uniqueness and identifiability. This paper presents a new approach for the identification of nonlinear interaction parameters of column outflow experiments. The procedure requires no a priori assumptions on the shape of the underlying interaction process functions. Employing experimental data sets on cadmium and anthracene breakthrough as case studies, possible applications of the new approach will be shown, and its features will be discussed. Error analysis based on singular value decomposition of the sensitivity matrix quantifies the identification error. Identification procedures without a priori shape information are superior to fixed parametrizations in diagnostic investigations, especially in cases without reliable a priori knowledge on the sorptive interactions.     

Insights for size-dependent reactivity of hematite nanomineral surfaces through Cu sorption

Macroscopic sorption edges for Cu²⁺ were measured on hematite nanoparticles with average diameters of 7 nm, 25 nm, and 88 nm in 0.1 M NaNO₃. The pH edges for the 7 nm hematite were shifted approximately 0.6 pH units lower than that for the 25 nm and 88 nm samples, demonstrating an affinity sequence of 7 nm > 25 nm = 88 nm. Although, zeta potential data suggest increased proton accumulation at the 7 nm hematite surfaces, changes in surface structure are most likely responsible for the preference of Cu²⁺ for the smallest particles. As Cu²⁺ preferentially binds to sites which accommodate the Jahn-Teller distortion of its coordination to oxygen, this indicates the relative importance of distorted binding environments on the 7 nm hematite relative to the 25 nm and 88 nm particles. This work highlights the uniqueness of surface reactivity for crystalline iron oxide particles with decreasing nanoparticle diameter.     

Removal of Cr from synthetic wastewater by sorption into volcanic ash soil

The possibility of using volcanic ash soils (VAS) or Andisols as a low-cost and natural adsorbent is investigated in this study for the removal of Cr (VI) from synthetic wastewater. Andisols can be used as adsorbent because they are characterized by the presence of non-crystalline secondary minerals such as allophane and imogolite that show variable charge characteristics and have the ability to retain cations and anions. The adsorption of Cr on to two VAS from Mt. Isarog and Mandalagan (B-Horizon), Philippines, was carried out at ambient temperature using batch adsorption studies. The effects of different parameters such as amount of adsorbent, contact time, initial Cr concentration and pH of the solution were investigated. The results showed that the VAS from Isarog is more effective in the removal of Cr than in Mandalagan. The maximum removal efficiency of the Isarog soil for a Cr concentration of 10mg/L reached 89% with a dose of 20 g/L at a moderately acidic pH of 3. The Mandalagan soil on the other hand could remove only 65% at the same pH conditions and parameters. The difference in the removal of the two soils may be attributed to their physico-chemical properties in which the Isarog soil has higher clay content, porosity and lower bulk density. Isarog soil has fine particles with higher surface area and more active non-crystalline minerals and thus has higher removal efficiency than Mandalagan soil. Based on the results, the use of VAS from Isarog appears to be economical and an alternative to commercially available adsorbents for the removal of Cr from contaminated wastewater.     

非饱和压实土率敏性及蠕变时效特征试验研究

为研究部分饱和状态下高填方回填土工后长期变形,对非饱和压实土在可控基质吸力下分别开展率敏性和蠕变试验,并分析两者间时效对应关系。率敏性试验采取不同加载速率的三轴剪切,分析基质吸力（0、100、200、300 kPa）、加载速率（0.40、0.02 mm/min）以及超固结比（1、4和8）对土体强度和变形特征的影响,并确定三轴剪切蠕变的三级加载应力水平为抗剪强度的0.45、0.65、0.85倍;在4种可控基质吸力（0、100、200、300 kPa）下参考陈氏加载法,按三应力水平分级加载开展非饱和压实土三轴剪切蠕变试验。试验结果表明：随着基质吸力的增加,其率敏性参数ρ 减小,其率敏性降低;随着基质吸力逐渐增大,其蠕变初始最大速率、稳定蠕变速率以及蠕变变形量均显著减小;蠕变试验确定的应变速率−应变关系线与率敏性试验获得的应变速率−应变数据点基本吻合,证明两者间存在一定时效对应关系,且随着基质吸力的增大,这种时效对应关系更显著。     

钴,锶在包气带土壤中迁移特征的试验研究

在中国辐射防护研究院试验场Ｃｏ＾２＋（ＣｏＣｌ２．６Ｈ２Ｏ），Ｓｒ＾２＋「Ｓｒ（ＮＯ３）２作喷淋液进行了１４４０ｈ的淋滤试验，得到了Ｃｏ＾２＋，Ｓｒ＾２＋在气带土壤中迁移的平均阻滞系数；