非均质土柱中溶质迁移的连续时间随机游走模拟

非均质介质中溶质迁移往往出现非费克现象,传统的对流弥散方程(ADE)则难以较好地描述这种现象.采用连续时间的随机游走理论(CTRW)研究1250cm长一维非均质土柱中溶质运移问题,探讨CTRW模型中参数及非费克迁移的变化特征.研究结果表明,β值的大小与介质的非均质特征有关,非均质性越强,β值越小,但β值具有相对的稳定性,然而ADE的弥散系数则具有随尺度增大而增大的现象.对于介质非均质性较强和非费克现象较明显的溶质穿透曲线,尤其是在拖尾部分,与ADE相比,CTRW具有较高的模拟精度.     

Assessment and prediction of contaminant migration in ground water from chromite waste dump

Sukinda chromite valley is one of the largest chromite deposits of the country and produces nearly 8% of chromite ore. It greatly contributes towards the economic development but at the same time deteriorates the natural environment. It is generally excavated by opencast mining method. In the Sukinda mining area, around 7.6 million tons of solid waste have been generated in the form of rejected minerals, overburden material/waste rock and sub-grade ore that may be resulting in environmental degradation, mainly causing lowering in the water table vis-à-vis deterioration in surface and ground water quality. The study conducted in and around one of the chromite mine of the valley reveals that the concentration of hexavalent chromium is found in the water samples of ground and surface water, mine effluents and seepage water. Hexavalent Chromium (Cr⁺⁶) have been found varying between 0.02 mg/l and 0.12 mg/l in mine effluents and 0.03–0.8 mg/l in shallow hand pumps and 0.05 and 1.22 mg/l in quarry seepage. The concentration of Cr⁺⁶ in Damsal nalah, the main surface water source in the area, is found varying between 0.03 mg/l and 0.14 mg/l and a increasing trend, which is in the downstream of mining activities, has been observed. Leachate study clearly shows that the soil lying in the vicinity of mine waste dump shows highest concentration of Cr⁺⁶. Contaminant migration in ground water depends upon various geohydrological conditions of the area. The study shows that aquifer resistivity varies between 15 Ωm to 150 Ωm and aquifer depth varies from 4 m to 26 m below ground level. The ground water flow and mass transport models were constructed with the help of geo-hydrological and geophysical informations using Visual Modflow software. Contaminant migration and path lines for 20 years have been predicted in two layers model of ground water. The study provided an insight into the likely migration of contaminant in ground water due to leaching from overburden dump of chromite ore and will be helpful in making strategic planning for limiting the contaminant migration in the ground water regime in and around the mining areas.     

矿山水土污染与防治对策研究

矿山水土环境污染是采矿活动引发的主要环境地质问题之一。我国矿山数量众多,水土污染比较普遍,尤以金属矿山最为严重,矿山水土污染防治是今后开展国土空间生态保护修复的重要内容。基于全国矿山地质环境摸底调查成果资料,对矿业活动不同阶段的水土污染风险以及不同矿山的水土污染类型、特征和污染物迁移演化规律等进行了研究。分析指出:矿业活动过程包括勘探、建矿、开采、洗选、冶炼等多个阶段,而水土污染风险贯穿于矿业活动全过程,不同阶段的污染风险不同;矿产资源开发造成的水土污染物类型、特征因开采的矿产类型不同而不同,呈现出特征污染物与矿体母岩的高度相关性;矿山及其周边污染物的迁移作用受污染物自身的物理化学性质和外界环境条件的影响,在矿山长期持续开采条件下矿山水土污染物存在累积效应,而矿产资源集中开采区的污染物扩散表现出叠加效应。通过对某典型水土环境污染案例的分析研究,初步证实了上述推断。根据我国矿山水土环境污染多发性和复杂性的特点,建议今后开展矿山水土污染防治工作应区分不同类型矿山、不同地质环境条件、不同污染物特征、不同污染程度,采取分类施策、系统修复、标本兼治的对策,以实现矿山环境明显改善。     

Modeling preferential water flow and solute transport in unsaturated soil using the active region model

Preferential flow and solute transport are common processes in the unsaturated soil, in which distributions of soil water content and solute concentrations are often characterized as fractal patterns. An active region model (ARM) was recently proposed to describe the preferential flow and transport patterns. In this study, ARM governing equations were derived to model the preferential soil water flow and solute transport processes. To evaluate the ARM equations, dye infiltration experiments were conducted, in which distributions of soil water content and Cl⁻ concentration were measured. Predicted results using the ARM and the mobile–immobile region model (MIM) were compared with the measured distributions of soil water content and Cl⁻ concentration. Although both the ARM and the MIM are two-region models, they are fundamentally different in terms of treatments of the flow region. The models were evaluated based on the modeling efficiency (ME). The MIM provided relatively poor prediction results of the preferential flow and transport with negative ME values or positive ME values less than 0.4. On the contrary, predicted distributions of soil water content and Cl⁻ concentration using the ARM agreed reasonably well with the experimental data, with ME values higher than 0.8. The results indicated that the ARM successfully captured the macroscopic behavior of preferential flow and solute transport in the unsaturated soil.     

浅谈小城镇地下水污染原因及其防治措施

本文分析了小城镇地下水污染的原因、途径及水文地质条件，提出了防治地下水污染的综合性措施。     

Pesticide transport and transformation modeling in soil column and groundwater contamination prediction

Pesticide transport and transformation were modeled in soil column from the soil surface to groundwater zone. A one dimensional dynamic mathematical and computer model is formulated to simulate two types of pesticides namely 2,4-dichlorophenoxy acetic acid and 1,2-dibromo 3-chloro propane in soil column. This model predicts the behavior and persistence of these pesticides in soil column and groundwater. The model is based on mass balance equation, including convective transport, dispersive transport and chemical adsorption in the phases such as solid, liquid and gas. The mathematical solution is obtained by finite difference implicit method. The model was verified with experimental measurements and also with analytical solution. The simulation results are in good agreement with measured values. The major findings of this research are the development of the model which can calculate and predict the concentration of pesticides in soil profiles, as well as groundwater after 4, 12, 31 days of pesticide application under steady state and unsteady water flow condition. With the results of this study, the distribution of various types of pesticides in soil column to groundwater table can be predicted.     

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.     

Institutional instruments for water pollution control

This paper focuses on the articulation of policies in the interface between economic production and water quality. One problem is the introduction, at this production-ecologic interface, of unwanted water-borne residuals by firms and municipalities. The policy objective is to absorb the social cost of environmental degradation into the production function within the two constraints of efficiency in the allocation of resources and the protection of property rights. The efficient allocation of environmental resources (in such a way as to maximize human welfare) has long been recognized as a basic objective in resource management. Equally important is the consideration of environmental rights and responsibilities in a society where property power and the institution of property is a dominant characteristic. Since the manner in which the property owner acts may affect the environment of his neighbours, it is important that policy instruments inform the holder of the property rights of the ill-effects of his actions upon others and induce him to take action to remedy the situation. The question of water quality management options requires urgent consideration for two reasons. Firstly, the cost of water pollution control is already considerable and is likely to increase even more sharply as the growing number of urban centres put greater pressure on the water resource for waste dilution and assimilation and other competing uses such as municipal demands, heat dissipation, recreation and wildlife protection. Secondly, the institutional mechanisms for dealing with this problem seem to be inadequate and ineffective. It is true that subsidies and grants have encouraged the building of more municipal waste treatment plants while regulation and court action have reduced some of the worst abuses. Subsidies and grants may be inefficient policy choices because they encourage hardware solutions even when other less expensive solutions are possible. In addition, they fail to inform the polluters of the ill-effects of their action; and the general public has to shoulder the burden in the form of increased taxation. Regulation and court action are cumbersome, sporadic and time-consuming. Effluent standards could be made flexible as a policy instrument if they afforded the polluter the opportunity to choose either to install in-plant controls or to pay the “fine” or to combine both these choices in any way that minimized his costs. This would combine the policy instrument of the effluent standard with the policy instrument of an effluent (or user) charge. The charges could be set either to reflect marginal pollution damages or the marginal cost of maintaining a given ambient standard. In other words the inferred marginal damage of pollution is equal to the marginal cost of treatment up to some desired level thus ensuring that the desired amount of waste load be reduced at least cost. Pricing and transferable effluent permits serve the same purpose.     

Modelling coupled heat and contaminant transport in groundwater

This paper presents the results of a research programme conducted on the geotechnical centrifuge at The University of Western Australia to investigate coupled heat and contaminant transport in the soil surrounding a buried waste source. The phenomena which govern heat and contaminant transport through porous media are discussed, the principles of geotechnical centrifuge modelling are outlined, and relevant scaling laws that govern the relationship between a centrifuge model and the prototype, with respect to the problem of coupled waste transport, are presented. A model test, simulating two-dimensional migration from a buried heat and contaminant source, is described, and the results from four model tests are presented. The experimental data show that hydraulic instability is responsible for the transport of contaminant in the soil around the source and that the mode of instability is determined by the magnitude of the effective Rayleigh number.     

Environmental pollution status assessment of water and soil in Langfang City

Through systematic sampling and analysis of water and soil in the planning area of Langfang City, employing national environmental quality standards, the qualities of groundwater and surface-water was overall evaluated. On the whole, the quality of deep-level groundwater was better and hazardous substances were not superstandard, F is higher, Fe and Mg was superstandard in several sites. The quality of shallow groundwater was general worse and COD, Fe, Mn, NH4^＋-N, F, total hardness, total dissolved solids etc. overstep drinking water standard; the quality of surface water was worst and many indices were evidently higher, which was very worst in the east of downtown. Main pollution way of water body was lixiviation type of primary pollution groundwater and infiltration type of secondary pollution groundwater. Environmental quality assessment of plough layer soil indicated that it was better in the northwest and worse in the southeast, furthermore from Xiwu, Daguanzhang, Zhougezhuang to Pengzhuang, Dazhaolin and the north of Jingshan railroad, the environmental quality is worst.     

河谷平原区地下水污染的途径——以齐齐哈尔市为例

本文以位于嫩江河谷平原的齐齐哈尔市为例,分析了河谷平原区地下水水质污染的途径,并提出了治理地下水污染的措施。     

浅谈地下水与土地沙化的关系

沙化,是我国主要的地质灾害之一.由于全球气候变暖,人类经济活动频繁等因素的影响,近年来,我国沙化的扩展速度不断加快,不仅使自然生态环境趋于劣化,还威胁人类的生存.因此,研究和探索沙化的形成和发展,寻觅控制沙化漫延的途径,是一件具有现实意义的事情.     

江西省南昌市地下水无机污染现状及其评价

介绍了南昌地区地下水类型、含水岩(层)组的空间分布和地下水的补给、径流、排泄条件及动态变化规律,阐述了研究区地下水主要污染源类型、数量及污染途径及水质量现状.文章从无机污染方面,对区内地下水污染现状进行了初步分析评价,并提出了防治建议.     

Experimental study on soil pollution analysis around tailings using ground penetrating radar

Pollution caused by tailings has become a serious environmental problem in China. An attempt was made to establish the ground penetrating radar （GPR） as a quick and non-destructive method for soil pollution analysis. Some physical models were established of contaminated soils from the tailing area. A series of indoor GPR experiments were conducted with 1 GHz antenna. The interface of contaminated area and uncontaminated area is characterized as a saltation zone in the radar image. The results of experiments show a clear correlation between the GPR data and the pollution intensity of soil. Based on all experimental data, the relation of velocity of electromagnetic wave propagation and pollution intensity was induced by using artificial neural network （ANN）. The results obtained indicate that GPR can provide high-resolution estimates of soil pollution variations around tailings as a function of depth as well as space and time.     

大气水—地表水—土壤水—地下水相互转化关系的试验研究

本文重点研究了有作物条件下不同供水农田的“四水”相互转化,突出了有作物条件下降水入渗、潜水蒸发的差异性,土壤水在农业生态环境中的重要性,为水资源多目标开发,探索新路子。     

Methylene blue transport in a sand-illite mixture and its implications for contaminant transport

Understanding contaminant transport in clay-containing soils is critical for accurate prediction of the travel distances of contaminants and for the design and implementation of corresponding remediation plans. This study examined the breakthrough behavior of methylene blue (MB) through sand-illite mixtures using laboratory soil-column experiments at five inlet concentrations, three flow rates, and five illite contents. Kinetic and equilibrium adsorption tests were performed to evaluate the maximum adsorption capacities of the sand and illite used in the soil-column experiments. In addition, the bed efficiency, MB saturation, and adsorption rate were calculated to quantitatively describe the observed breakthrough curves. The observed breakthrough curves, bed efficiencies, MB saturations, and adsorption rates in this study demonstrated the presence of a threshold illite content of ~10% for the adsorption efficiency of contaminants. This implies the need to evaluate the threshold clay content for accurate predictions of contaminant transport through gap-graded clay-containing soils.

     

裂隙岩体中污染物运移过程的数值模拟

基于双重介质理论模型建立了污染物在地下环境中运移的耦合数学模型,给出了有限元离散的数值格式。并以核废料储存过程中核素90Sr为例,采用所建立的数值模型模拟其在裂隙岩体中运移过程,预测了污染物的浓度分布范围和发展趋势。模拟结果表明:核素90Sr在处置库中运行40年后,下游地区的抽水井的浓度可达到3 100 Bq/m3,超出了国家规定的标准,为固体废物场址的选择以及污染的控制提供了决策依据。