TDR detection of nonaqueous phase liquids in sandy soils using the eigendecomposition method

In this study, the presence of nonaqueous phase liquids (NAPL) in sandy soils are detected using a TDR probe system and the eigendecomposition method of analysis. As a demonstration, five NAPLs with different physicochemical properties (acetone, benzene, heptane, trichloroethylene, and xylene; Table 1) were used. Samples were prepared in such a way that the soil pore fluid has different contents of deionized water and NAPLs. For each experiment, a pulse signal with known characteristics was used and reflected signals were captured by an oscilloscope and analyzed using the eigendecomposition method. Autoregressive modeling and singular value decomposition were used to calculate the eigenvalues. The most significant eigenvalues were identified based on their power spectrum. The relative eigenvalue of the first mode (Eow), which is a measure of the power carried by the signal, was calculated and correlated to NAPL type and content, and octanol water partition coefficient (log Kow). The results indicated that for the same NAPL content, as log Kow increases, Eow decreases due to increase of hydrophobicity. For the same log Kow, as the organic content in soil pore fluid increases, Eow increases due to decrease of dielectric properties of the pore fluids.     

非饱和土中热−湿−盐耦合作用的稳态分析

以多孔介质理论为基础,研究了稳态条件下非饱和土中温度?水分?盐分多场耦合问题。考虑非饱和土的孔隙被液态水、溶解的盐分、水蒸气和干燥气体等填充,在质量和能量守恒的基础上获得了非饱和土中水分、气体、盐分的质量守恒方程以及能量守恒方程。考虑一维稳态问题,选取温度、孔隙气压、孔隙水压和盐溶液浓度以及它们的导数作为状态变量,得到了问题的状态方程组。在给定的边界条件下,采用打靶法求解了该强耦合的非线性变系数微分方程组,通过与已有的试验结果相比较,验证了模型的有效性。基于数值算例,参数分析了含水率、温度边界、孔隙率等条件对非饱和土中温度场、水分场和盐分场分布的影响规律。     

Effect of salt concentration on desiccation cracking behavior of GMZ bentonite

Bentonite has been proposed for use as an engineering barrier and buffer in nuclear waste repositories and has been used frequently in municipal waste landfills. The cracking behavior and deformation properties of this material can be influenced by the chemistry of pore water. In the present work, the influence of salt concentration on the desiccation cracking behavior of GMZ bentonite was investigated with laboratory experiments. Image processing techniques and SEM tests were performed on the specimens which had undergone the desiccation testing in order to analyze the cracking mechanisms. Results show that the water evaporation process can be identified by a steady rate stage, a falling rate stage and a residual stage. The water evaporation rate is strongly affected by the salt concentration of the pore water; higher salt concentrations result in lower evaporation rates; the final water content is strongly impacted by a high initial salinity; otherwise the water contents are very similar for the residual stage. During desiccating, most of cracks appeared at the steady evaporation stage. The cracking morphology and patterns were greatly affected by the salt concentration of the pore water; and larger crack lengths and lower crack densities were obtained as the initial salinity was increased.     

农田土壤水分和盐分的空间变异性及其协同克立格估值

通过对一块面积为1hm2麦田内的98个观测点取样分析,测定了两个时期的土壤水分和盐分含量。结果表明两个时期的土壤含水量均服从正态分布,底层盐分均服从对数正态分布,而表层的盐分分布具有不确定性。两个时期土壤水分和盐分的变异系数分别属于弱变异和中等变异强度。通过结构分析,发现两个时期的水分和盐分均在一定范围内存在空间相关性。对两个时期土壤水分和盐分空间分布的动态变化进行了比较,同时采用CoKriging方法进行估值,与Kriging法相比,其估计方差减少百分数最大达到了136.3%。     

核磁共振与水文地质钻探联合技术确定盐湖晶间卤水层富水性

中国西部大型干旱盆地盐湖中,承压卤水含水层因其中所赋存的固--液相钾矿资源储量大而成为主要含矿层。采用地面核磁共振与水文地质钻探相结合的技术方法对柴达木盆地某盐湖进行的承压卤水可采性试验,获取了含水层的相关物理参数,并将其解译为相关的水文地质参数。通过水文地质综合判断,确定了含水率 5. 4% 的富水地段。水文地质钻探验证获取了稳定丰富的涌水量,并使之成为采卤量 1. 5 ×104m3/d、KCl 含量 1. 67% 的工业性开采水源地。结果表明,核磁共振与水文地质钻探联合技术是确定盐湖晶间卤水层富水性的可靠右有效的方法。     

硫酸钠盐渍土土-水特征曲线的试验与理论研究

土-水特征曲线（SWCC）在非饱和土力学中扮有重要的角色,是非饱和土力学研究的核心问题。以西北地区黄土中含有的典型硫酸钠盐为变化因素,采用滤纸法测得了兰州黄土及不同含盐量黄土状硫酸钠盐渍土的基质吸力并绘制土-水特征曲线,通过试验测试和理论分析来解释硫酸钠盐分对黄土状硫酸钠盐渍土基质吸力的影响规律,以期为工程实践提供一定的理论依据。结果表明：相同含水率下硫酸钠盐渍土的含盐量越高,基质吸力越大。以非饱和土力学理论和表面物理化学理论为基础,考虑了土中的盐分对基质吸力的毛细部分及吸附部分的影响,得到了土中含盐量与基质吸力关系的半经验公式。利用该公式计算得到不同含盐量硫酸钠盐渍土的土-水特征曲线,计算曲线与试验曲线吻合程度较高,表明该公式可以很好地描述盐渍土中不同含盐量与基质吸力的关系。     

Effect of sodium chloride on the metabolic activity of halophilic bacteria isolated from the Lake Gardno estuary

The effect of different concentrations of sodium chloride on the metabolic activity of halophilic bacteria derived from the Lake Gardno estuary was studied using respirometric methods. The influence of salt was examined in two ways: the bacteria were preincubated in various concentrations of sodium chloride, and the cells used for respirometric measurements were supplied with substrates dissolved in water amended with various concentrations of the salt. Generally, an increase in the concentration of sodium chloride in the medium used for preincubation resulted in an increase in metabolic activity. Conversely, a decrease was noted when solutions of increasing salt content were employed to dissolve the substrate. The decrease in oxygen uptake noted when increased amounts of salt were added is proposed to be the result of the short period allowed for adaptation of cells to the higher salt concentrations.     

盐分对土的冻结温度及未冻水含量的影响研究

利用测温法和核磁共振法测量了不同浓度典型盐溶液（NaCl、Na2CO3）饱和重塑粉土的冻结温度及冻结特征曲线，并与不同浓度的NaCl、Na2CO3纯溶液作对比分析，研究初始含盐量对冻结温度及未冻水含量的影响。结果表明：土样冻结温度随初始含盐量的增加而逐渐降低；相同浓度NaCl溶液饱和土样的冻结温度低于相应纯溶液的冻结温度，但相同浓度 （<0.6 mol/L）Na2CO3溶液饱和土样的冻结温度却比纯溶液的冻结温度高；同一负温下，土样中未冻水含量随NaCl初始含盐量的增加而增多，但随Na2CO3初始含盐量的变化不明显。通过机制分析，表明盐类型和含盐量对土水势具有不同的影响。基于改进的广义Clapeyron方程，将含盐分土冻结温度表达式引入未冻水含量预测模型，得到了能够考虑不同含盐量影响的土体未冻水含量的定量表达，并与实测数据进行对比，验证了该模型能够较为合理的预测不同温度下含盐土体的未冻水含量。     

Major and trace element geochemistry of superficial sediments and suspended particulate matter of shallow saline lakes in Eastern Austria

General geochemical parameters of water, superficial sediments, and suspended particulate matter (SPM) were determined from small shallow saline lakes (soda ponds) as well as from lake Neusiedlersee in eastern Austria. Additionally, instrumental neutron activation analysis (INAA) was used to determine the distribution of major, rare earth and other trace elements in superficial sediments and SPM. Chemical results show remarkable differences in salinity and ionic strength between the investigated ponds. Anthropogenic effects, such as drawdown of ground water level and a loss of lake water due to drainage, are clearly reflected in obtained chemical and geological data. Due to a strong dependence of the complexation and scavenging behavior of the rare earth elements (REE) on ionic strength, a significant difference between REE concentrations in soda ponds with different anthropogenic impact was found. The content and composition of authigenic evaporitic minerals in superficial sediments and SPM clearly differ with a fluctuating water level and salt concentration. Furthermore, we determined the distribution of major and trace elements in superficial sediments of a nearby fluvial system. Our results show a clear correlation between REE superficial sediment concentrations in anthropogenically degraded soda ponds and fluvial system. Therefore, we assume that REE concentrations of sediments and SPM are suitable for the study of geochemical changes of inland saline lakes due to anthropogenic impacts on water balance.     

非饱和含盐土壤水扩散系数试验研究

在室内用水平土柱吸渗法对不同含盐量、不同溶液浓度和不同土类的土壤水扩散系数进行了试验研究.试验结果表明:土壤水(或盐水)扩散系数与土壤的体积含水量之间具有指数函数的关系,且随着含水量的降低而减小.当同一类土在干容重和含水量相同时,土壤水扩散系数是随土中含盐量的增多而增大,以粗粒土最为明显.不同浓度的盐水在土壤中运行时,其盐水的扩散系数是随盐水浓度的增大而减小.     

基于核磁共振与氮吸附技术的黄土含盐量对结合水膜厚度的影响研究

结合水膜是一种结合水,对深层黄土渗透与物理力学性质有重要影响,而水膜厚度是其中最为关键的参数。因黄土结构的特殊性及其微观性,结合水膜厚度一般不能通过实验手段直接测得,因此文章基于核磁共振技术与氮吸附试验展开重塑黄土孔隙溶液中含盐量对结合水膜厚度的影响研究。试验结果表明:（1）结合水与自由水的热力学性质不同,低温冻融试验显示黄土内结合水冰点约为-3.3℃,而自由水的冰点则要高于结合水冰点;同时两者在T2驰豫时间上的表现也不相同,通过核磁共振试验分析得到了两者的横向驰豫时间界限-T2截止值为1.65 ms。（2）黄土中结合水膜厚度与土体孔隙溶液内含盐量呈线性负相关,随着含盐量的增加,结合水含量降低,结合水膜厚度不断减小。黄土中含盐量的增加导致结合水膜变薄,水膜厚度的减小又会导致结合水抗剪强度降低,深层黄土渗透性增强。本次试验首次将核磁共振技术与氮吸附法相结合,应用于黄土含盐量与结合水膜厚度关系研究中,试验方法对试样无损伤,且测试快速便捷,具有较高的可靠性,为研究盐渍土中水的赋存状态提供了新思路。     

基于WorldView-Ⅱ高分数据的盐湖矿化度含量定量反演研究——以尕斯库勒盐湖为例

鉴于盐湖水体矿化度含量定量反演研究较少,且中、低空间分辨率遥感数据反演的矿化度含量精度偏低,文章以柴达木盆地西部尕斯库勒盐湖为例,基于WorldView-Ⅱ高空间分辨率遥感数据和实测矿化度数据,开展了盐湖湖表水体矿化度含量定量反演技术研究。通过开展盐湖水际线提取、盐湖水体矿化度光谱诊断特征分析、矿化度识别遥感指数构建、矿化度遥感信息分离和线性回归模拟,构建了盐湖矿化度含量定量反演模型。经评价,模型反演精度为96.61%。研究结果表明,基于WorldView-II高分数据定量反演盐湖矿化度含量的方法是有效的,该方法对于快速定量识别盐湖矿化度含量,降低盐湖矿化度调查和分析成本,预测富矿水域具有十分重要的意义。     

硫酸钠盐渍土未冻水含量的实验研究

土体中的未冻水含量影响冻土的物理力学性质,也是评价冻土中水分迁移的重要指标.利用核磁共振技术对含有不同浓度硫酸钠溶液的兰州黄土的未冻水含量进行测试,并分析了温度、含盐量对未冻水含量的影响.同时,测试了不同含盐量下黄土的液塑限及液塑限含水率下土体的冻结温度,计算了不同含盐量下的未冻水含量并与实测值进行比较,给出了不同含盐量下幂函数方程w_u=at^-b中的参数值.在此基础上,分析了-5、-10、-15和-20℃条件下未冻水含量随含盐量的变化规律,建立了4个温度下不同含盐量区间的未冻水-含盐量拟合公式.     

Analytical solution for one‐dimensional consolidation of unsaturated soils using eigenfunction expansion method

This paper introduces an exact analytical solution for governing flow equations for one‐dimensional consolidation in unsaturated soil stratum using the techniques of eigenfunction expansion and Laplace transformation. The homogeneous boundary conditions adopted in this study are as follows: (i) a one‐way drainage system of homogenous soils, in which the top surface is considered as permeable to air and water, whereas the base is an impervious bedrock; and (ii) a two‐way drainage system where both soil ends allow free dissipation of pore‐air and pore‐water pressures. In addition, the analytical development adopts initial conditions capturing both uniform and linear distributions of the initial excess pore pressures within the soil stratum. Eigenfunctions and eigenvalues are parts of the general solution and can be obtained based on the proposed boundary conditions. Besides, the Laplace transform method is adopted to solve the first‐order differential equations. Once equations with transformed domain are all obtained, the final solutions, which are proposed to be functions of time and depth, can be achieved by taking an inverse Laplace transform. To verify the proposed solution, two worked examples are provided to present the consolidation characteristics of unsaturated soils based on the proposed method. The validation of the recent results against other existing analytical solutions is graphically demonstrated. Copyright © 2013 John Wiley & Sons, Ltd.     

受载荷的湿土结冰温度变化规律的研究

介绍４种不同土质的不同含水率及含盐量的湿土，在０￣２０ＭＰａ外载范围内结冰温度的变化规律及数值，对含盐量与外载的交互作用进行试验研究表明，除不饱和水的砂外，结冰温度与外载变化规律均服从克拉柏龙方程，含盐对结冰温度的影响服从溶液结冰温度降低的规律。含盐与外载交互作用甚微，并获得湿土的结冰温度与外载，含水率，含盐量的变化规律及数值。     

长江河口盐沼湿地酸挥发性硫化物的时空分布特征及影响因素

以长江河口典型潮间带(崇明东滩湿地)不同地貌单元植被根际柱样沉积物(0~33 cm)为研究对象,探讨了长江河口潮间带表层沉积环境中酸挥发性硫化物(AVS)的时空间变化特征及其与环境因子的关系.结果表明,不同植被根际沉积物中 AVS 含量存在显著季节变化,表现为:互花米草大于海三棱藨草和芦苇.各采样点根际沉积物中 AVS 含量垂向变化为:高潮滩芦苇,随深度的增加而降低;中潮滩互花米草与海三棱藨草,随深度的增加先增大后减小,且在地面下约20 cm 处显著增大. Pearson 相关分析表明,沉积物中 AVS含量与<16μm 的颗粒物、有机碳含量及含水率之间不存在简单的正相关关系.根际沉积物中 AVS 含量的时空变化可能受潮汐、植被生长等因素的综合影响,其时空变化特征反映了长江河口潮滩复杂多变的氧化还原条件.与芦苇和海三棱藨草相比,入侵物种互花米草对沉积物中硫酸盐异化还原有显著影响,其可能改变了潮滩湿地生态系统原有的氧化-还原生物地球化学循环过程     

The influence of mineralogy and texture in the water content of rock salt formations. Its implication in radioactive waste disposal

The consideration of the use of salt formations as possible radioactive waste disposal sites led us to attempt to determine the extent to which their brine content could influence the performance of the disposal system. Bedded rock salt from the Cardona, Zaragoza and Guendulain Fms., as well as diapiric rock salt from northern and southeastern Spain, have been selected and their water contents characterized by thermogravimetry. Free water content (intergranular water and water in fluid inclusions) in the studied formations ranges from 0.01 to 1.24% weight. In addition, the presence of hydrated minerals increases the amount of total water in the rock (up to 3.50%). Clear differences between the studied formations are observed in the total amount of water and in the form of water entrapment in rock salt. The results obtained have allowed the classification of the studied rock salt formations with respect to their free-brine content as water-poor (around 0.1% in average), intermediate water-rich (around 0.2%) and water-rich (higher than 0.3%). The petrographical features of the rock salt, such as mineralogical content and halitic textures, play an important role in its water content. Whilst brine in fluid inclusions is related to the halite texture, intergranular brine depends mainly on the content of clay and sulphate minerals.     

Numerical study of soil heterogeneity effects on contaminant transport in unsaturated soil (model development and validation)

The movement of chemicals through soil to groundwater is a major cause of degradation of water resources. In many cases, serious human and stock health implications are associated with this form of pollution. The study of the effects of different factors involved in transport phenomena can provide valuable information to find the best remediation approaches. Numerical models are increasingly being used for predicting or analyzing solute transport processes in soils and groundwater. This article presents the development of a stochastic finite element model for the simulation of contaminant transport through soils with the main focus being on the incorporation of the effects of soil heterogeneity in the model. The governing equations of contaminant transport are presented. The mathematical framework and the numerical implementation of the model are described. The comparison of the results obtained from the developed stochastic model with those obtained from a deterministic method and some experimental results shows that the stochastic model is capable of predicting the transport of solutes in unsaturated soil with higher accuracy than deterministic one. The importance of the consideration of the effects of soil heterogeneity on contaminant fate is highlighted through a sensitivity analysis regarding the variance of saturated hydraulic conductivity as an index of soil heterogeneity. Copyright © 2011 John Wiley & Sons, Ltd.     

Conceptual hydrosalinity model for prediction of salt load from wastewater flows into soil and ground water

Dynamic hydrosalinity models are available, but are not used extensively on a large scale soil which receives wastewater from industrial areas, partly because adequate database are expensive to be obtained. Thus, for this reason, there is an urgent need to assess the salt and other pollutant loads collected in wastewater flows into the soil and/ or ground water systems. A conceptual hydrosalinity model was used on two major underlying principals of mass balance and steady state. This model was initially tested on the 4,117 km² plains west of the Yazd-Ardakan district in the central part of Iran. This model was used at a time when the soil and ground water salinity problem was serious due to the high shortage of water. It was possible to calibrate the model with ± 2 % of the flow volume and total dissolved solids of the industrial wastewater discharge from over 2,000 factories. The verification results were 98 % of the measured values. Moreover, this model was tested for the verification of the model data from the analysis of 36 wells’ water in the area where industrial wastewater discharge was used. The results showed that most of the indices of total dissolved solids, total suspended solids, biological oxygen demand and chemical oxygen demand are above standard levels. The results of the model can be used for the management practice of the reduction of salt pollutant load in the area to achieve sustainable development for location of industries in the study area.