水封石油洞库污染物运移规律研究

水封石油洞库储油可能造成地下水污染。明晰石油污染物在裂隙岩体中的运移规律是库区地下水污染防控的前提。为揭示石油污染物在洞周围岩地下水中的运移规律,基于裂隙-孔隙双重介质模型,采用数值模拟方法研究了石油中的特征污染物——苯的运移扩散过程,并分析了裂隙倾角、裂隙开度、基质渗透率和纵向弥散度对苯运移规律的影响。研究表明:储库正常运行50 a后,苯的迁移被限制在较小的范围内,不会到达水幕系统,也不会进入到地面表层下的水体中。在长期运行条件下,相邻洞周围岩中的污染晕可相互连通,并将引起相邻洞罐中油品污染物之间的交叉污染。苯的竖向污染距离对纵向弥散度和裂隙倾角大小敏感性强,而对裂隙开度和基质渗透率的敏感性较弱。洞室间岩柱中轴线上苯的最大浓度对裂隙倾角最为敏感,且随裂隙倾角和基质渗透率的增大而减小,随纵向弥散度和裂隙开度的增加而增大。     

新疆某火电厂厂区和灰场土层弥散试验研究

为天池能源五彩湾电厂地下水环境影响评价提供基础数据,本文以新疆五彩湾地区不同类型的土壤为研究对象,以NaCl为示踪剂,在室内进行土柱水动力弥散试验,得到不同类型土壤的弥散系数。穿透曲线测定结果表明,氯离子在运移时穿透曲线大致分为两个阶段,穿透曲线呈逐渐上升并最终达到稳定的趋势。     

迁移机理下污染物场地隔离屏障的设计研究

重点对迁移机理下污染物填埋场地天然粘土隔离屏障的厚度设计展开研究.运用溶质在饱和土中迁移的一维平流-弥散运移模型,根据影响污染物迁移的基本参数(弥散系数、阻滞因子等),对饱和土隔离屏障建立一套估算污染物击穿屏障的时间、对指定的击穿浓度和设计寿命确定屏障厚度的设计分析方法,绘制了一些便于工程应用的设计图表,分析了扩散系数...     

考虑介质均衡吸附时的室内弥散试验数据分析方法

文中对描述一维、稳定渗流与连续定浓度注入示踪剂的砂柱弥散试验的近似解析解进行反函数变换 ,建立了在多孔介质与示踪剂间为均衡吸附条件下 ,能够计算多孔介质纵向弥散度与阻滞系数的方法。而且 ,这种方法在介质的有效孔隙率为已知的情况下 ,还可以计算出多孔介质对示踪剂的吸附系数     

裂隙介质溶质运移试验研究

介绍了自行研制的裂隙介质溶质运移试验测试系统,与国内外同类试验装置相比,该测试系统可以对不同尺寸的裂隙介质进行溶质运移试验,在裂隙介质中布设了测试流体压力、温度、浓度的传感器,可以对原样裂隙中各点的溶液浓度进行直接测量,以此来获得溶质在裂隙介质中的运移规律。应用该测试系统进行了NaCl示踪剂溶液在裂隙介质中运移的试验,并用解析–优化方法求解了裂隙介质中NaCl示踪剂溶液运移的水动力弥散参数。     

非线性吸附条件下填埋场污染物运移过程二维数值分析

假设填埋场下部为三层结构体系,且渗流场稳态,建立了污染物二维运移控制方程。在控制方程中分别考虑垃圾降解效应、压实黏土衬里的非线性吸附特性、滞水层与含水层的线性吸附特性及各向异性。采用数值分析方法对某一假想填埋场进行具体计算。通过变动参数计算与分析,计算结果表明:压实黏土衬里和滞水层的垂直弥散系数为污染物二维运移的敏感因素。仅考虑压实黏土衬里的非线性吸附特性下,复合参数Sl,m为污染物运移的敏感因素,当Sl,m取值较大时,污染物的水平向运移能力增强,而对吸附强度Kl,l不敏感。滞水层线性吸附对污染物运移影响显著而含水层吸附性影响较弱。     

沙质滩涂中反应性与非反应性污染物阻滞效应研究

沙质滩涂受到石油污染后,滩涂-水系统中的石油污染物处在一个物理、化学、生物的相互联系和连续变化之中。为了定量地研究滩涂-水系统反应性石油污染物的动态变化规律,通过水动力弥散实验和一维对流、弥散模型确定了水分和溶质在滩涂-水系统的水-盐动力学参数和反应动力学参数。选择研究区代表性沙样S和Y进行试验,研究结果表明,对于沙质滩涂-水系统中的非反应性污染物,S沙样和Y沙样的渗透系数分别为1.95cm/min和0.76cm/min,弥散系数分别为0.156cm~2/min和0.463cm~2/min;对于沙质滩涂-水系统中的反应性污染物,S沙样和Y沙样的阻滞系数分别为2.55和2.30,分配系数分别为1.93cm~3/g和1.05cm~3/g。     

衰减源作用下固结压力及吸附参数对污染物运移规律的影响

固结变形会导致粘土防渗层的结构特性和渗透特性发生改变,影响渗流场和浓度场的分布,进而影响污染物在防渗层中的运移规律。在比奥固结理论的基础上,考虑线性吸附模式,研究了污染物在小变形土体中的运移规律,分析了衰减源作用下,固结压力与线性吸附系数对污染物运移过程的影响。结果表明,与不考虑固结作用相比,固结作用延迟了污染物的运移,使得污染物运移深度减小,并且随着固结压力的增大,固结作用对污染物运移的延迟作用逐渐增强;在线性吸附模式情况下,污染物运移深度减小率随着吸附系数的减小逐渐增大,说明固结作用对污染物运移的延迟作用随着吸附系数的减小而越来越凸显。     

污染物运移过程的一维数值分析

考虑填埋场中固体废弃物的生物降解效应和含水层中土颗料对污染物的吸附性,在有限深度条件下基于对流、弥散和地球化学反应等污染物运移机理,提出了填埋场污染物运移过程数值模拟的一维计算模型。进而采用半解析方法进行数值求解,通过变动参数比较分析确定了控制填埋场污染物运移过程的主要参数。具体数值计算表明:污染物在含水层中运移浓度将于某一特定时间达到峰值,随后逐渐降低。粘土垫的厚度及其渗透性、压缩粘土垫层与含水层的吸附能力是填埋场污染物运移的重要近控制参数。     

应用物理非平衡CDE模型反演岩溶管道流参数

应用物理非平衡CDE模型能够模拟岩溶区示踪剂穿透曲线(TBCs)从而获取岩溶管道水文地质参数。相对传统模型而言,该模型将岩溶管道内液体分为流动区域和非流动区域,更能体现岩溶管道的非均质性和穿透曲线的拖尾现象。本次研究通过自动监测示踪剂浓度和流量变化绘制穿透曲线并结合QTRACER2程序计算模型所需参数初始值,确定示踪试验回收率,并应用物理非平衡CDE模型模拟岩溶管道内平均速度、弥散系数、两区间分配系数和质量交互系数。最后通过不同距离处示踪剂穿透曲线对比发现平均速度和弥散系数随距离的增大而增大,具有明显的尺度效应,而分配系数和质量交换系数基本不变。为降低尺度效应的影响,本文采用算数平均计算速度和弥散系数。     

Model based prognosis of contaminant leaching for reuse of demolition waste in construction projects

In this study, groundwater contamination from recycled demolitian waste in road constructions is assessed using predictions of leachate concentrations. Numerical transport simulations are performed for three scenarios (a parking lot, a noise protection barrier, and road), and using a number of characteristic subsoils of Germany, to estimate the breakthrough of different contaminant classes at the groundwater table. Conservative tracer breakthrough times (BTT) primarily depend on subsoil hydraulic properties, for organic pollutants KOC and subsoil OC are the controlling parameters. Significant concentration reductions from dispersion only occur when source concentrations decrease prior to contaminant breakthrough. If source concentrations remain high for long periods relative to peak BTT, concentration breakthrough is undamped. Accounting for biodegradation reduces breakthrough concentrations significantly. For the “noise protection barrier” and “road” scenarios, capillary barrier effects cause the seepage water to partially bypass the recycling material. Accounting for this bypass flow and spatial averaging across the constructions reduces concentrations by about 30–40?%.     

Colloid dispersion on the pore scale

Dispersion describes the spreading of a tracer or contaminant in an aquifer. Detailed knowledge of dispersion is the key to successful risk assessment in case of groundwater pollution or groundwater protection. The dispersion of colloids on the pore scale is controlled by flow velocity, ionic strength, colloid size, colloid concentration, and colloid-matrix interactions. The objective of this study was to provide quantitative data and to assess the scale dependency of colloid dispersion on the pore scale. The positions of carboxylated polystyrene microspheres (1 μm, 0.5 μm) were recorded during transport experiments in silicon micromodels with three pore topologies. The positions were combined into particle trajectories revealing the flow path of individual colloids. More than thousand trajectories were evaluated for each experiment to obtain the dispersivity of the colloids for flow distances between 10 and 1000 μm. All experiments were run at high Peclet numbers. The pore scale dispersivity was on the order of 8-30% of the flow distance with pure water, dependent on the heterogeneity of the pore topology. The dispersivity was positively correlated with the ionic strength and inversely correlated with the colloid size and the flow velocity. A coating of the micromodel surface with humic acid also increased dispersivity. The quantitative data set presented here supports the theoretical framework for colloid transport and allows to parametrize colloid transport on the pore scale.     

Modeling and testing of reactive contaminant transport in drinking water pipes: chlorine response and implications for online contaminant detection

A modified one-dimensional Danckwerts convection-dispersion-reaction (CDR) model is numerically simulated to explain the observed chlorine residual loss for a "slug" of reactive contaminants instantaneously introduced into a drinking water pipe of assumed no or negligible wall demand. In response to longitudinal dispersion, a contaminant propagates into the bulk phase where it reacts with disinfectants in the water. This process generates a U-shaped pattern of chlorine residual loss in a time-series concentration plot. Numerical modeling indicates that the residual loss curve geometry (i.e., slope, depth, and width) is a function of several variables such as axial Péclet number, reaction rate constants, molar fraction of the fast- and slow-reacting contaminants, and the quasi-steady-state chlorine decay inside the "slug" which serves as a boundary condition of the CDR model. Longitudinal dispersion becomes dominant for less reactive contaminants. Pilot-scale pipe flow experiments for a non-reactive sodium fluoride tracer and the fast-reacting aldicarb, a pesticide, were conducted under turbulent flow conditions (Re=9020 and 25,000). Both the experimental results and the CDR modeling are in agreement showing a close relationship among the aldicarb contaminant "slug", chlorine residual loss and its variations, and a concentration increase of chloride as the final reaction product. Based on these findings, the residual loss curve and its geometry are useful tools to identify the presence of a contaminant "slug" and infer its reactive properties in adaptive contaminant detections.     

地下水水质模型的 Taylor 展开随机模拟方法

地下水水质模型是由水流问题和水动力弥散问题耦合而成。本文从Ｔａｙ－ｌｏｒ展开式入手，结合有限元等方法，直接推导某节点浓度的均值和方差、协方差的表达式，把水流问题和水动力弥散问题统一进行考虑，避免了计算过程中随机变量的增加，提高了计算效率，为地下水水质模型的随机模拟提供了新的计算方法。     

Physical modelling of solute transport in porous media: evaluation of an imaging technique using UV excited fluorescent dye

The development and evaluation of a 2-dimensional physical model, which is designed to assist in the characterisation of complex solute transport problems in porous media, is described. The laboratory model is a transparent 2-dimensional porous media of nominal thickness and uses a non-invasive imaging technique in conjunction with a fluorescent dye tracer (sodium fluorescein) to monitor solute movements. Under ultraviolet (UV) illumination the dye emits visible light which is imaged by a CCD (Charge Coupled Device) camera. The image is processed to estimate the 2-dimensional distribution of tracer concentrations. The system can successfully model a simple contaminant plume within a homogenous porous matrix constructed from glass beads (60-100 microm). Experimental results show that transverse dispersion coefficient was 3.9 x 10(-10) m2/s when sodium fluorescein transported in porous matrix with a walter velocity of 5.71 x 10(-6) m/s. The low transverse dispersion coefficient suggests that the molecular diffusion of solute cannot be neglected under low velocity of the water. The advantages of using UV rather than an ordinary light system are a reduction in noise and experimental errors. Errors due to light dispersion within the model are shown to be negligible for the current model. Since contaminant with aromatic rings are usually fluorescent and biological samples can be labelled by fluorescent dye, this imaging technique using UV excited fluorescent dye will be used to investigate biodegradation process in porous media.     

Fuel-grade ethanol transport and impacts to groundwater in a pilot-scale aquifer tank

Fuel-grade ethanol (76L of E95, 95%v/v ethanol, 5%v/v hydrocarbon mixture as a denaturant) was released at the water table in an 8150-L continuous-flow tank packed with fine-grain masonry sand. Ethanol, which is buoyant and hygroscopic, quickly migrated upwards and spread laterally in the capillary zone. Horizontal migration of ethanol occurred through a shallow thin layer with minimal vertical dispersion, and was one order of magnitude slower than the preceding bromide tracer. Dyes, one hydrophobic (Sudan-IV) and one hydrophilic (Fluorescein) provided evidence that the fuel hydrocarbons phase separated from the E95 mixture as ethanol was diluted by pore water and its cosolvent effect was diminished. Most of the added ethanol (98%) was recovered in the effluent wells that captured the flow through the high water content regions above the water table. Complementary bench-scale 2-D visualization experiments with E95 confirmed hydrocarbon phase separation, residual NAPL formation and migration within the capillary fringe. These results corroborate previous bench-scale studies showing that ethanol has high affinity for vadose-zone pore water and can migrate through the capillary zone. The pilot-scale tank experiment provides the first hydrocarbon and ethanol concentration measurements (and thus, quantification of impacts to groundwater quality) from a subsurface spill of E95 in a well-characterized system with a well-defined source. It also provides the first quantitative near-field-scale evidence that capillarity can significantly retard the vertical dispersion and horizontal advection of ethanol. Such effects could be important determinants of the extent of ethanol migration and longevity as well as groundwater impacts.     

Vorkommen und Verhalten eines Arzneimittels (Clofibrinsäure) im Grundwasser

As to nowadays knowledge drugs in groundwater originate from anthropogenic input by urine and production residue. Clofibric acid, a blood lipid regulator is one of the human drugs already detected in groundwater and drinking water with concentrations of up to 7300 ng/l. Recent investigations indicate, that some drugs are insufficiently or not degraded by sewage treatment or by drinking water production. Groundwater contamination is likely to be due to leaky sewage systems, influent streams and bank infiltration. The distribution of clofibric acid beneath the sewage farms south of Berlin shows the high mobility of this contaminant. Nevertheless, results indicate that there is no correlation between the concentrations of clofibric acid and physico-chemical parameters, groundwater constituents nor sediment material. First results of a column experiment show that clofibric acid is transported with tracer velocity, although some variations in concentration of clofibric acid occur. Again, no correlation between clofibric acid and pH, oxygen content nor the concentration of groundwater constituents has been found whereas a possible dependence of the redox potential on clofibric acid was observed. During the column experiment no sorption processes could be identified, but there were hints for a degradation of clofibric acid.     

Application of microbial enumeration technique to evaluate the occurrence of natural bioremediation

Natural bioremediation is believed to be the major processes that account for both containment of the petroleum-hydrocarbon plume and reduction of the contaminant concentrations. In this study, the feasibility of applying the microbial enumeration technique was assessed for natural biodegradation evaluation at three selected gasoline spill sites. At each site, two monitor wells were installed along the groundwater flow, and one multilevel sampler (MLS) was installed to delineate the vertical distribution of the contaminant plume. Two continuous soil cores were collected at each site to evaluate the horizontal distribution of the microbial activity. Soil samples were used for microbial enumeration, grain-size distribution analysis, and sediment extraction. In situ tracer study was performed using 1,2,4-trimethylbenzene (1,2,4-TMB) as the tracer to study the efficiency of contaminant biodegradation. Investigation results demonstrate the agreement between microbial enumeration and other evaluation techniques for natural bioremediation (e.g., geochemical indicator analysis, tracer study). Results suggest that the microbial enumeration is useful in assessing the occurrence, efficiency, and status of the bioremediation. Because this technique provides insight into factors controlling contaminant biodegradation, it could be performed as the supplemental method for natural bioremediation evaluation at petroleum-hydrocarbon spill sites.     

基于对流弥散反应方程的渗透反应墙设计方法

渗透反应墙(PRB)是一种将通过墙体的污染物转化为无害物质或者将其沉淀降解的原位处理法。在考虑分子扩散、机械弥散、对流、吸附和降解等耦合情况下,建立了污染物通过PRB运移的数学模型。针对不同地下水渗流场和边界条件的组合,推导了一系列降解条件下模型的稳态解,并针对四氯乙烯给出了设计曲线。PRB两边的地下水渗流场对其厚度具有较大的影响,对流弥散同向情形所需厚度最大,纯扩散次之而对流弥散反向厚度最小;且最大的差别可达1 m。研究表明,有限域与半无限域出口得出的曲线图差别不大,尤其是对于对流-弥散同向和纯扩散情形。这两个工况得到的计算结果差别在10%以内。本文解可用于渗透反应墙的初步设计和试验数据拟合等。     

Effects of intensive urbanization on the intrusion of shallow groundwater into deep groundwater: examples from Bangkok and Jakarta

Asian megacities have severe pollution problems in both coastal and urban areas. In addition, the groundwater potential has decreased and land subsidence has occurred because of intensive groundwater pumping in urban areas. To prevent the adverse effects of urbanization on groundwater quality, it is necessary to confirm the changes in groundwater flow and contaminant transport caused by urbanization. We examined the effects of urbanization on contaminant transport in groundwater. The research areas were located around Bangkok, Thailand, and Jakarta, Indonesia, cities with populations of approximately 8 and 12 million, respectively. Each metropolitan city is located on a river delta and is adjacent to a bay. We measured the water level and collected water samples at boreholes at multiple depths (100 to 200 m) in 2004 and 2006 in Bangkok and Jakarta, respectively. The current hydraulic potential is below sea level in both cities because of prior excess abstraction of groundwater. As a result, the direction of groundwater flow is now downward in the coastal area. The Cl(-) concentration and delta(18)O distributions in groundwater suggest that the decline in hydraulic potential has caused the intrusion of seawater and shallow groundwater into deep groundwater. Concentrations of Mn and NO3(-)-N in groundwater suggest the intrusion of these contaminants from shallow to deep aquifers with downward groundwater flow and implies an accumulation of contaminants in deep aquifers. Therefore, it is important to recognize the possibility of future contaminant transport with the discharge of deep groundwater into the sea after the recovery of groundwater potential in the coastal areas.