Efficient hydrologic tracer-test design for tracer-mass estimation and sample-collection frequency, 1, method development

Hydrological tracer testing is the most reliable diagnostic technique available for the determination of basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test design can be difficult because of a lack of prior knowledge of the basic hydraulic and geometric parameters desired and the appropriate tracer mass to release. A new efficient hydrologic tracer-test design (EHTD) methodology has been developed to facilitate the design of tracer tests by root determination of the one-dimensional advection-dispersion equation (ADE) using a preset average tracer concentration which provides a theoretical basis for an estimate of necessary tracer mass. The method uses basic measured field parameters (e.g., discharge, distance, cross-sectional area) that are combined in functional relationships that describe solute-transport processes related to flow velocity and time of travel. These initial estimates for time of travel and velocity are then applied to a hypothetical continuous stirred tank reactor (CSTR) as an analog for the hydrological-flow system to develop initial estimates for tracer concentration, tracer mass, and axial dispersion. Application of the predicted tracer mass with the hydraulic and geometric parameters in the ADE allows for an approximation of initial sample-collection time and subsequent sample-collection frequency where a maximum of 65 samples were determined to be necessary for describing the predicted tracer-breakthrough curve (BTC). Inclusion of tracer retardation and decay cause a net increase in tracer-mass estimates so that the preset average tracer concentration will be maintained and there will be a consequent steepening of the BTC, but retardation also causes BTC spreading and a delay in tracer arrival.     

A review of some tracer-test design equations for tracer-mass estimation and sample-collection frequency

Determination of necessary tracer mass, initial sample-collection time, and subsequent sample-collection frequency are the three most difficult aspects to estimate for a proposed tracer test prior to conducting the tracer test. To facilitate tracer-mass estimation, 33 mass-estimation equations have been developed over the past century. These 33 equations are reviewed here, 32 of which were evaluated using previously published tracer-test design examination parameters. Comparison of the results produced a wide range of estimated tracer mass, but no means is available by which one equation may be reasonably selected over the others. Each equation produces a simple approximation for tracer mass. Most of the equations are based primarily on estimates or measurements of discharge, transport distance, and suspected transport times. Although the basic field parameters commonly employed are appropriate for estimating tracer mass, the 33 equations are problematic in that they were all probably based on the original developers experience in a particular field area and not necessarily on measured hydraulic parameters or solute-transport theory. Suggested sampling frequencies are typically based primarily on probable transport distance, but with little regard to expected travel times. This too is problematic in that tracer sampling remains a haphazard process that tends to result in false negatives or data aliasing. Simulations from the recently developed efficient hydrologic tracer-test design methodology (EHTD) were compared with those obtained from 32 of the 33 published tracer-mass estimation equations and suggested sampling frequencies. EHTD applies functional relationships developed from hydrologic measurements in a solute-transport model to develop a preliminary tracer-breakthrough curve that has been shown to reasonably predict actual tracer-test results.     

水文频率分布模型的异同性与参数估计问题

回顾了20世纪50年代对水文频率分布模型异同性的认识,分析了分布模型在统计特征上的相异性与共通性。在分布的几何形态相同的条件下,目前所用的分布模型中,仅3个参数的模型基本上是相异的。通过观察与实例分析,初步发现,取4个参数,有可能使模型有统一的求解结果。用数学方法能得到参数的唯一解,但多数方法是先计算出不确定性较大的C_S值,继而据此算得其它一个或两个参数,故这种结果是一种初值,有待通过合理性分析,才能得到最终取用值。     

Analytical hydrologic models and the design of policy instruments for groundwater-quality management

This paper explores how analytical hydrologic models can inform the effective design and choice of policy instruments to manage groundwater quality by coupling a social-planner’s problem of optimal groundwater-quality management with analytical solutions from the hydrology literature. A theoretical analysis is performed in order to characterize the properties of an optimal emissions policy. The model is then applied in a numerical analysis of groundwater contamination by chloride from highway deicers, demonstrating the relevance of the theoretical results to practical management settings. This analytical approach can help determine which policy instruments are likely to be effective in controlling groundwater pollution, especially if costly numerical groundwater models are not available for the aquifer in question. Unlike previous economic studies of groundwater contamination, this approach defines optimal emissions policies as a function of geophysical parameters employed by hydrologists such as distance between source and sink, groundwater velocity, and aquifer dispersivity. The theoretical section of this paper also demonstrates that the relationship between geophysical parameters and optimal emissions levels may be ambiguous.     

分布式水文模型构建理论与方法述评

回顾了分布式水文模型的发展历程,分析总结了分布式水文模型的构建理论与方法,并对其关键内核——“物理基础”的含义做了深入而新颖的分析。分析了两类当前比较活跃的模型——分布式物理模型与分布式概念性模型中存在的问题及发展前景,并探讨了综合二者之长的具有物理基础的松散型分布式水文模型的构建思路,以及学者们期待中的基于确定性与随机性耦合的分布式水文模型。     

Identification of hydrologic and geochemical pathways using high frequency sampling,REE aqueous sampling and soil characterization at Koiliaris Critical Zone Observatory,Crete

Koiliaris River watershed is a Critical Zone Observatory that represents severely degraded soils due to intensive agricultural activities and biophysical factors. It has typical Mediterranean soils under the imminent threat of desertification which is expected to intensify due to projected climate change. High frequency hydro-chemical monitoring with targeted sampling for Rare Earth Elements (REE) analysis of different water bodies and geochemical characterization of soils were used for the identification of hydrologic and geochemical pathways. The high frequency monitoring of water chemical data highlighted the chemical alterations of water in Koiliaris River during flash flood events. Soil physical and chemical characterization surveys were used to identify erodibility patterns within the watershed and the influence of soils on surface and ground water chemistry. The methodology presented can be used to identify the impacts of degraded soils to surface and ground water quality as well as in the design of methods to minimize the impacts of land use practices.     

The system pargasite-H2O-CO2: a model for melting of a hydrous mineral with a mixed-volatile fluid—I. Experimental results to 8 kbar

The stability of the amphibole pargasite [NaCa₂Mg₄Al(Al₂Si₆))O₂₂(OH)₂] in the melting range has been determined at total pressures (P) of 1.2 to 8 kbar. The activity of H₂O was controlled independently of P by using mixtures of H₂O + CO₂ in the fluid phase. The mole fraction of H₂O in the fluid ($\text{X}{}_{\mathrm{H}}{}_2\text{O}{}^{\mathrm{1fl}}$) ranged from 1.0 to 0.2.At P < 4 kbar the stability temperature (T) of pargasite decreases with decreasing $\text{X}{}_{\mathrm{H}}{}_2\text{O}{}^{\mathrm{1fl}}$ at constant P. Above P ? 4 kbar stability T increases as $\text{X}{}_{\mathrm{H}}{}_2\text{O}{}^{\mathrm{1fl}}$ is decreased below one, passes through a T maximum and then decreases with a further decrease in $\text{X}{}_{\mathrm{H}}{}_2\text{O}{}^{\mathrm{1fl}}$. This behavior is due to a decrease in the H₂O content of the silicate liquid as $\text{X}{}_{\mathrm{H}}{}_2\text{O}{}^{\mathrm{1fl}}$ decreases. The magnitude of the T maximum increases from about 10°C (relative to the stability T for $\text{X}{}_{\mathrm{H}}{}_2\text{O}{}^{\mathrm{1fl}}\text{= 1}$) at P = 5 kbar to about 30°C at P = 8 kbar, and the position of the maximum shifts from $\text{X}{}_{\mathrm{H}}{}_2\text{O}{}^{\mathrm{1fl}}\text{? 0.6}$ at P = 5 kbar to $\text{X}{}_{\mathrm{H}}{}_2\text{O}{}^{\mathrm{1fl}}\text{? 0.4}$ at P = 8 kbar.The H₂O content of liquid coexisting with pargasite has been estimated as a function of at 5 and 8 kbar P, and can be used to estimate the H₂O content of magmas. Because pargasite is stable at low values of $\text{X}{}_{\mathrm{H}}{}_2\text{O}{}^{\mathrm{1fl}}$ at high P and T, hornblende can be an important phase in igneous processes even at relatively low H₂O fugacities.     

级联分样与分频段功率谱计算的大地电磁张量阻抗估算对比

级联分样和分频段功率谱计算是大地电磁数据处理中的两种功率谱计算方法.本文基于Welch方法,在其他各项处理参数设置相同的条件下,分别将两种功率谱计算方法用于模拟数据和实测数据对比计算.计算结果认为,在无噪声的模拟数据条件下,两种功率谱计算方法得到的测深曲线差异不明显;对实测数据的计算发现,高频部分级联分样要略优于分频段功率谱估计,而在低频部分,分频段功率谱估计的测深曲线连续性与误差情况要好于级联分样.     

Chemical exchange during hydrothermal alteration of basalt by seawater—II. Experimental results for Fe,Mn, and sulfur species

Fresh mid-ocean ridge basalts of varying crystallinity and an andesite were reacted with seawater and with a Na-K-Ca-Cl solution at 200–500°C and 500–1000 bar in sealed gold capsules. $\text{Water}\text{rock}$ mass ratios of one to three were used and durations ranged from two to twenty months. The concentrations of Fe, Mn, and reduced and oxidized sulfur species in solution reached steady state in most of the experiments at 400–500°C, but not in those at 200–300°. The concentrations of Fe and Mn were a few ppm at 200–300° and increased greatly with temperature between 300 and 500°. The low values at 200–300° are probably related to the uptake of Fe and Mn by smectite at the in situ pH, which was slightly acid at 200° and slightly alkaline at 300°. The quench pH values decreased with increasing temperature above 300°. The only reliable data for the concentration of Zn in solution were obtained at 400°, where values 1–2 ppm were found. Copper was extensively leached from basalt and andesite and was deposited as part of a Cu-Au alloy in the capsule walls or, in some experiments, as chalcopyrite.Reduced sulfur was readily leached from basalt into solution, and was also produced by the reduction of seawater sulfate by ferrous iron derived from the basalts. The proportion of seawater sulfate which was reduced in the experiments with a $\text{water}\text{rock}$ ratio of one varied from 5–10% at 300°C to > 95% at 500°. The rate of sulfate reduction depended on the run temperature, on the crystallinity and initial sulfur content of the rocks used as starting materials, and on the $\text{water}\text{rock}$ ratio. The final concentration of reduced sulfur in solution increased greatly with temperature, and generally exceeded that of Fe on a molal basis.The oxide-sulfide assemblages produced in the experiments resemble those in the basalt-seawater geothermal system at Reykjanes, Iceland, and in hydrothermally altered basalts and gabbros from the oceanic crust; they include pyrite, pyrrhotite. chalcopyrite, hematite, and probably magnetite. The particular assemblage varied systematically with the temperature, rock type, and crystallinity of each run. Anhydrite precipitated in all experiments with seawater, at all temperatures from 200–500°C. However, its persistence to the end of the runs was apparently metastable, as it should have reacted with the final solutions to produce pyrite or pyrrhotite.     

高效稠油井筒清理和修复技术

结合生产实践，介绍了稠油井井筒清理技术的高效套、磨铣技术，井下液压生力器解卡技术；井筒修复技术的套管整形技术，套管补贴技术，取换套工艺技术。     

Experimental rock deformation: techniques, results and applications to tectonics

Flow and fracture of rocks in the Earth's crust and upper mantle are evident from the study of rocks in the field, but the same features can be induced in laboratory experiments on rocks at high temperatures and pressures. Through such experiments, the mechanical and other properties can be measured, and used to constrain quantitative modelling of lithospheric dynamics.     

An internally consistent thermodynamic dataset with uncertainties and correlations: 2. Data and results

Abstract This, the second of two papers, represents the application of a least squares approach, discussed in the previous paper, to the generation of an internally consistent thermodynamic dataset involving 60 reactions among 43 phases, in the system K₂O–Na₂O–CaO–MgO–Al₂O₃–SiO₂–H₂O–CO₂. We make the assumption that all the thermodynamic data, with the exception of enthalpies of formation of the phases, are well known, and solve for an internally consistent set of enthalpies which reproduces the 60, experimentally determined, phase equilibrium reactions. An important difference between our dataset and that of previous alternatives in the literature is that we are able to determine the uncertainties on, and correlations between, the enthalpies of formation for all phases in the set, and hence are able to apply simple error propagation techniques to determine the uncertainties in any phase equilibrium calculations performed using this dataset. Selection of reactions, for geothermometry and geobarometry, may be more readily made by choosing equilibria with small uncertainties in their thermodynamics. Our data are in reasonably close agreement with the high temperature molten oxide calorimetry results on silicate minerals where available, a fact which lends a degree of confidence to the results.     

Experimental study on impact signal frequency spectrum and energy distribution characteristics of water-stone flow

Geotechnical and Geological Engineering - Understanding of impact characteristics is the basis of studying the hydrodynamic characteristics of water–rock flow. The impact and vibration...     

西安地铁2号线通过地裂缝的结构及防水设计

首建南北走向的地铁2号线是西安市规划轨道交通线网中一条重要的南北干线,其建设中的难题和关键技术就是跨越地裂缝的问题.文中结合西安市地铁2号线地裂缝段工程措施的研究课题,对地裂缝的特点进行了说明,对地铁区间结构穿过地裂缝处的所采取的结构设计措施和防水设计方案进行了论述.针对地裂缝的活动性,提出了过地裂缝段采取的防治措施是:"防"与"放"相结合,结构适应地裂缝的变形为主;结构断面扩大,预留变形空间,结构分段增设变形缝以便适应变形、接头采用柔性连接,加强结构强度以适当抵抗变形对结构的破坏;同时在地裂缝处理段采取可调式框架板轨道适应地裂缝处变形,来保证运营安全;在防水措施上采取特殊方法,设计了具有大应变特性的新型独特的防水方案.     

Garnet-biotite thermometer and estimation of crystallization temperature of zoned garnets from metapelites: II. Effect of X_{H_2 O} on estimation accuracy

The fluid regime of medium-grade metapelitic systems was studied with mineral fugometers. It has been established that at least some of the rocks under consideration contain mineral assemblages equilibrated with the participation of fluids with an appreciably lowered mole fraction of the aqueous component (0.4–0.7). The data obtained are used to explain the systematic discrepancy between the temperature estimated with the garnet-biotite geothermometer and the program THERMOCALC. It has been suggested that the negative correlation between the temperature intervals of crystallization and the nucleation temperature of the studied garnets is related to the kinetic features of porphyroblast growth.     

实验矿物物理的发展现状与趋势:2.弹性和波速

弹性性质和波速是矿物重要物理性质. 实验测量的弹性性质和波速与地震学观测结果的对比,是确定地球内部物质组成、理解地球内部圈层结构形成机制和揭示地球内部物质分布不均一性最为直接和重要的手段. 在过去20年,伴随大腔体压机、金刚石压砧、同步辐射X光、激光加热等技术的快速发展,在地球内部相应温度和压力下测量主要构成矿物的弹性性质和波速取得了巨大进展. 综述了矿物物理在地球内部矿物弹性性质和波速实验测量的发展历史、近20年的研究现状与趋势,并展望了该学科未来发展的方向、关键科学问题与面临的主要挑战.      

Chloride transfer in cement‐based materials. Part 2. Experimental study and numerical simulations

This second part of the work deals firstly with carrying out materials characterization, mainly mercury intrusion porosimetry and chloride electrodiffusion tests on two cement pastes. Experimental data allowed fixing the perturbation parameter ? and other dimensionless numbers highlighted in part I of this work. Secondly, a series of parametric simulations were performed in order to compute the chloride diffusion coefficient through a gradual complexity of the elementary cell, approaching as close as possible the real microstructure of the cement pastes tested. Results highlighted that taking into account microstructure parameters (porosity, tortuosity and constrictivity) allows to approach the experimental diffusion coefficient. However, they also showed that electrochemical interactions between ions and the liquid‐solid interface, and the multi‐scale character of cementitious material microstructure, must be considered. Copyright © 2012 John Wiley & Sons, Ltd.     

注CO2提高煤层气采收率的模拟实验研究

根据煤储层的吸附/解吸机理,模拟煤层气井"排采-注气-排采"的生产过程,进行CH4、CO2的单相气体吸附/解吸和CO2注入置换煤层CH4的实验,得到了CH4和CO2二元气体相组分变化数据和CH4和CO2混合气体的相分离图解.结果表明,在CH4和CO2二元气体的竞争吸附中,CO2组分的吸附速率是先快后慢,而CH4组分的吸附速率先慢后快,解吸时则相反.反映了CO2组分在与CH4组分的竞争吸附中占据优势,优先被吸附;同时发现注入气体数量越大,注入气体中CO2组分浓度越高,单位压降下的CH4解吸率和CO2吸附率越高.实验结论对工业规模的煤层气开发试验具有一定的指导意义.