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1.
The study presents results on the informativity and spatial variation of soil aggregation characteristics in one of the Critical Zone Observatories (CZO) in Europe – Fuchsenbigl, Austria. Water stable aggregates of different size were measured, and strong relationships between soil aggregation estimates were found. The horizontal variation of water stable aggregates at particular depths can be explained by certain vertical heterogeneity of the soil profiles in space. The water stable aggregates in 1–3 mm size dry aggregates in the upper layer vary from 44% to 76% under native vegetation, drop to 1% under intensive cultivation, and comprise 19% in land not tilled for 5 years. The results allow linking the characteristics of soil structure with other biotic and chemical properties for better estimation of the driving forces for soil aggregate formation. 相似文献
2.
动态光散射技术原位表征天然有机质存在下纳米零价铁的团聚效应 总被引：1，自引：1，他引：0
纳米零价铁原位修复地下水污染是近年发展起来的新技术,通过改性合成不同种类纳米零价铁可以克服其易团聚易氧化的问题,水体中存在的天然有机质也会对纳米铁的分散性和反应活性产生影响,因此开展原位测试并研究不同种类纳米铁在水中的团聚效应具有重要意义。本文对实验合成的纳米零价铁、羧甲基纤维素包覆纳米零价铁、膨润土负载纳米零价铁以及商用纳米零价铁,基于动态光散射技术(DLS),运用纳米粒度/Zeta电位分析仪,结合透射电子显微镜(TEM)和沉降光谱曲线等手段,对比研究了天然有机质(腐植酸HA)对纳米铁团聚效应的影响。结果表明,羧甲基纤维素包覆或膨润土负载改性提高了纳米零价铁颗粒的分散稳定性,有效抑制了团聚沉降,团聚体粒径分布在1000 nm以下。HA会吸附在纳米铁颗粒表面,从而增加静电排斥力,进一步减缓了团聚效应,尤其是对膨润土负载纳米零价铁的影响最为显著,其团聚体粒径能降至100 nm以下,沉降速率也极大减缓,分散稳定性表现最佳。本研究表明DLS结合TEM表征纳米颗粒是获得更加丰富的微观粒子信息的一种非常重要的手段。 相似文献
3.
Experimental deformation of partially melted granitic aggregates 总被引：16，自引：1，他引：16
Abstract The effects of varying amounts of partial melt on the deformation of granitic aggregates have been tested experimentally at conditions (900°C, 1500 MPa, 10-4 to 10-6/s) where melt-free samples deform by dislocation creep, with microstructures approximately equivalent to those of upper greenschist facies. Experiments were performed on samples of various grain sizes, including an aplite (150 μm) and sintered aggregates of quartz-albitemicrocline (10–50 and 2–10 μm). Water was added to the samples to obtain various amounts of melt (1–15% in the aplite, 1–5% in the sintered aggregates). Optical and TEM observations of the melt distribution in hydrostatically annealed samples show that the melt in the sintered aggregates is homogeneously distributed along an interconnected network of triple junction channels, while the melt in the aplites is inhomogeneously distributed. The effect of partial melt on deformation depends an melt amount and distribution, grain size and strain rate. For samples deformed with ? 1% melt, all grain sizes exhibit microstructures indicative of dislocation creep. For samples deformed with 3–5% melt, the 150 μm and 10–50 μm grain size samples also exhibit dislocation creep microstructures, but the 2–10 μm grain size samples exhibit abundant TEM-scale evidence of dissolution-precipitation and little evidence of dislocation activity, suggesting a switch in deformation mechanism to predominantly melt-enhanced diffusion creep. At natural strain rates melt-enhanced diffusion creep would predominate at larger grain sizes, although probably not for most coarse-grained granites. The effects of melt percentage and strain rate have been studied for the 150 μm aplites. For samples with ? 5 and 10% melt, deformation at 10–6/s squeezes excess melt out of the central compressed region allowing predominantly dislocation creep. Conversely, deformation at 10-5/s produces considerable cataclasis presumably because the excess melt cannot flow laterally fast enough and a high pore fluid pressure results. For samples with 15% melt, deformation at both strain rates produces cataclasis, presumably because the inhomogeneous melt distribution resulted in regions of decoupled grains, which would produce high stress concentrations at point contacts. At natural strain rates there should be little or no cataclasis if an equilibrium melt texture exists and if the melt can flow as fast as the imposed strain rate. However, if the melt is confined and cannot migrate, a high pore fluid pressure should promote brittle deformation. 相似文献
4.
Jan Blachowski 《Environmental Earth Sciences》2014,71(3):1327-1338
Rock minerals such as dimension and crushed stones and sands and gravels (aggregates) are indispensable materials for the building and construction industries. The growth in demand for these resources causes intensification of mining operations (and their consequent environmental impacts) and transport problems in regions abundant in rock minerals. The balanced management of these resources by regional policy-makers is difficult as it requires, among other things, comprehensive and up-to-date information on the spatial distribution and temporal changes of available reserves, demand, production, and transport. This information can be provided by means of spatial and temporal analyses through geographic information systems (GIS). In this research, the focus is on the following aspects of rock mineral (aggregates) resources and mining management in the context of regional spatial planning in the example region of Lower Silesia in Poland: the spatial and temporal changes in distribution and intensity of mining, the availability of economic reserves in active mines, the magnitude and distribution of road transport flows of aggregates, the potential of railways as an alternative means of transport, and the valorisation of undeveloped aggregates deposits to assess their suitability for future use. For the purposes of this study, cartographic models have been developed using GIS to facilitate analyses of these mineral resources, mining, and transport. The results of these analyses provide current and comprehensive information on the state of aggregates mineral resources, production and transport in the Lower Silesia region. They also give an insight into availability of rock mineral resources for the future. Knowledge of these processes is important for spatial development planning, especially physical infrastructure, conducted by national, regional, and local governments. 相似文献
5.
《International Geology Review》2012,54(1):65-72
Chert-plus-pyrite pebbles have been known for some time in a number of Witwatersrand conglomerates, but their distribution is highly variable. A wide variety of textures in chert-plus pyrite pebbles are documented here, and these textures place constraints on the origin of such pebbles. Replacement of chert pebbles by pyrite is indicated (pyrite grains and aggregates continue across many pebble boundaries), and both distributional and textural evidence favors a post-burial timing for this process. Significant mobility of sulfur after burial is indicated. Whether this replacement was diagenetic or metamorphic is not certain. 相似文献
6.
在煤层气开发过程中,煤粉聚集及沉降会堵塞煤层气运移通道及导致卡泵、埋泵等事故。为了查明不同粒度煤粉的聚集及沉降特征,选取粒度>140目（<106 μm）、>70~140目（106~<212 μm）和>50~70目（212~<300 μm）3种粒度范围的煤粉,开展了在去离子水中煤粉的聚集及沉降实验,从煤粉聚集及沉降特征观察、悬浮液中煤粉含量及煤粉粒度分布探究不同粒度煤粉在去离子水悬浮液中的聚集及沉降特征。结果表明,随着静置时间的增加,各粒度煤粉悬浮液的颜色均不同程度地变浅,逐渐出现分层,其中,粒度>140目的煤粉悬浮液最先出现分层。煤粉粒度越小,煤粉悬浮液顶部漂浮的煤粉量越多;煤粉粒度越大,其下沉到煤粉悬浮液底部的煤粉量越多。不同粒度煤粉悬浮溶液中煤粉含量均随着静置时间的增加呈现不同程度的降低,在停止搅拌后3 min内,煤粉含量下降最快,粒度为>70~140目的煤粉悬浮液中煤粉含量最大。根据不同粒度煤粉悬浮液中煤粉粒度分布曲线,将煤粉聚集及沉降过程分为3个阶段:单峰变双峰阶段（煤粉快速上浮及沉降）、双峰变单峰阶段（煤粉快速聚集及沉降）和单峰阶段（煤粉缓慢沉降）。粒度>140目的煤粉在悬浮液中最先达到缓慢沉降阶段,粒度>70~140目的煤粉在悬浮液中最后到达缓慢沉降阶段。从煤粉的受力、扩展的DLVO理论及煤粉的有机分子结构方面探讨了煤粉聚集沉降的机理:煤样含有大量的脂肪烃和芳香烃等疏水性基团,疏水性强,润湿性低;随着煤粉粒度的减小,其比表面积显著增大,煤粉表面吸附大量空气,形成气膜;同时,煤粉颗粒间相互吸附聚集,内部形成很多微孔隙,导致粒度小的煤粉易聚集漂浮在悬浮液面上。实验得到的不同粒度煤粉的上浮、下沉及悬浮情况,为后期煤层气开发中煤粉管控措施提供依据。 相似文献
7.
Commodities such as oil and gas occur in isolated reservoirs or accumulations, more generically called basic units here. To understand a study area’s economic potential and to craft plans for exploration and development, resource analysts often aggregate (sum, accumulate) basic unit magnitudes in distinct spatial subsets of the study area and then appraise the total area’s potential by summing these intermediate sums. In a probabilistic approach, magnitudes are modeled as random variables. Some have asked, “Do different methods of partitioning basic units into subsets lead to different probability distributions for the sum of all basic unit magnitudes?” Any method of aggregation of basic unit magnitudes which obeys the rules of probability leads to the same probability distribution of the sum of all unit magnitudes as that computed by direct summation of all basic unit magnitudes. A Monte Carlo simulation of a synthetic example in which the magnitude of resource in each unit is marginally lognormal and pairwise correlations among basic unit magnitudes are specified illustrates key features of probabilistic aggregation. The joint distribution of certain pairs of aggregates are closely approximated by a bivariate lognormal distribution. 相似文献
8.
As a major type of soil internal erosion, suffusion is causative for many geotechnical problems of earth structures and foundations. Although full laboratory tests are laborious, it is inevitable for susceptible soils. However, a good quick assessment can define those susceptible soils by eliminating quickly very stable and unstable soils from consideration. Traditional assessment methods often correlate and combine some predefined fixed particle sizes representing coarse and fine fractions of soils. This paper presents a novel, simple assessment method for identifying susceptibility to suffusion based on the general curvature of particle size distribution of soils. The further down a particle size distribution departs from its mean line, the more likely it behaves suffusive. The new assessment method has been tested against experimental data, and the results show some good correlation. 相似文献
9.
表征单元体(REV) 的存在是应用连续介质力学方法对岩体进行研究的前提,REV可以从岩体块体化程度的角度进行研究,裂隙大小及其统计分布是影响岩体块体化程度REV的重要因素。本文利用课题组自主研发的GeneralBlock 软件,建立更一般化实际化的模型,研究裂隙延展性统计分布的离散程度对岩体块体化程度REV的影响。分析时选取了最常用的裂隙延展性统计分布形式:正态分布。由于所建立的岩体结构模型是随机的,需要对每个随机裂隙模型进行多次实现。为节省计算量,当研究范围比较小时,对每种结构的每个研究范围进行9次随机实现。当研究范围足够大,达到REV大小的时候进行100次随机实现。为确定离散程度对表征单元体的影响,本文针对5个不同标准差进行了模拟分析（共建立了1 005个裂隙模型,分别进行了块体识别并计算其块体化程度B）。结果表明,裂隙延展性服从正态分布的情况下,如果其平均值一定,岩体的块体化程度随着统计分布离散程度的增加略有上升,裂隙岩体的REV值基本上由裂隙延展性统计平均值决定。 相似文献
10.
Experiments indicate that at the high wind velocities characteristic of portions of the Martian surface, sand-sized particles will break down to silt and clay, which will then inevitably form sand-sized aggregates. Basalt and olivine aggregates held together by electrostatics were produced in an eolian abrasion device and their mass properties studied. It was difficult to examine aggregates after formation, as they separate and reform with very little handling, since electrostatic binding forces are quite weak.It is shown that aggregates range from 60 to more than 600 μm in diameter, that they generally are spheroidal in shape and become more elongate with increasing size, and that they tend to be layered with the inner portions more tightly bound than outer layers. After about one-and-one-half years, some aggregates lose their charge which is replaced with moisture; the aggregates retain their original sizes and shapes. None of the properties of electrostatic aggregates so far investigated are incompatible with the presence of these materials on Mars. 相似文献
11.
Understanding a quarry in terms of its potential for breakwater construction materials presents a special challenge for the engineering geologist. Unlike blasting in aggregates and mining operations, optimisation of the extraction process has a focus on the potential for production of large blocks for armourstone. These blocks weighing many tonnes are used for cover layers to resist wave action. The quarry-run is used for breakwater core. If the quarry has been developed as a source of materials dedicated to a breakwater construction project, the success of the project depends greatly on the blasting and production of rock sizes that are required and the avoidance of leaving a massive quantity of unused materials behind in the quarry after project completion. Prediction of in-situ block sizes such as from joint spacing data, provides the most critical input for the prediction of the blast pile block size distribution (BBSD), which in turn is a vital early design input if the constructed breakwater is to be economical as well as effective.This paper is part of a series of papers that introduces the coastal engineering motivation for this work on engineering geology, giving reasons why the prediction of the fragmentation curve of the blast products in a dedicated quarry is of such economic importance for breakwater projects. The first step towards blasted block size distribution (BBSD) prediction is the prediction of the in-situ block sized distribution (IBSD), the main subject of this paper. Drawing together research methods from the 1990s and the rock mechanics principles of discontinuity analysis, a practical step by step methodology for IBSD assessment that includes approaches that are not reliant on specialised computer software is presented. Continuing on the practical theme, a new extension of the volumetric joint count approach is suggested for IBSD prediction for the case when sparse borehole data is all that is available. A case study of IBSD assessment and the associated BBSD and blast assessment is presented from a Carboniferous limestone quarry. For clarity, details of blast design and yield curve prediction that are recommended for use in the context of armourstone production, have been presented in a companion paper. The Rosin-Rammler equation is used as an example form for the BBSD prediction of a dedicated quarry and the potential for breakwater project optimisation is illustrated. The final section sets out a method for directly comparing yield curves together with the demand for materials set by the breakwater design. On the same plot, sizes where there is a relative shortfall in production can be identified. The dependence of effective breakwater design on accurate quarry yield prediction and quarry blasting performance is discussed. 相似文献
12.
岩溶是某垃圾焚烧环保发电站场场址勘察的主要不良地质作用,为了查明岩溶和破碎带的分布情况,本文利用高密度电阻率法来探测能引起低阻异常的岩溶等地质体。在调查该区地层和溶洞的类型、分布及电性特征的基础上,利用RES2Dmod建立包含不同规模和埋深的低阻溶洞或破碎带模型,通过对比模型的温纳、偶极和微分三种装置类型的正反演结果,在本地区选用分辨率和稳定性高的温纳装置进行高密度勘测。利用高密度电阻率法查明了两个落水洞的埋深和分布情况,推测了4个疑似溶洞和破碎带,部分与后期验证钻孔吻合。利用合适的装置类型进行高密度探测可以查明充水充泥低阻溶洞的规模及分布,是一种经济有效的场址勘察方法。 相似文献
13.
This paper is concerned with the structure and dynamics of modern retail facilities in Israel. It presents the first comprehensive
quantitative study of the recent trends in Israeli retail. On the basis of an unique database that includes sizes and locations
of retailers for a number of years, we test and challenge some of the traditional theories, as well as the latest approaches
to the analysis of urban systems. Recent approaches view cities as self-organizing systems and utilize complexity theory and
concepts of order. In the case of Israeli retail application of alternate methods of analysis suggests that the conventional
regularities such as rank-size rule, as is implied by the central place theory or the more general power law do not hold.
The findings reveal that the sizes of modern retailers display an exponential distribution, consistent across time and scale.
This signifies a presence of stable regularity in the structure of retail sizes. Exponential distribution of the retail sizes
is shown to reflect a lack of interdependence between the existing and the planned retail facilities. The issue of order versus
randomness and self-organization in the size distribution of retailers remains debatable and requires further development
of tools and universal criteria for analyzing complex systems. 相似文献
14.
通过对菲律宾棉兰老岛北端的迪纳伽特岛铬铁矿进行考察,介绍菲律宾共和国铬铁矿的分布概况,迪纳伽特岛铬铁矿资源的类型、分布、规模等情况,并将收集到的当地矿山建设外部条件及投资环境作简介,对该地区感兴趣的投资者可以起到参考和了解的作用。 相似文献
15.
It is generally agreed that particle size distributions of sediments tend ideally to approximate the form of the lognormal probability law, but there is no single widely accepted explanation of how sedimentary processes generate the form of this law. Conceptually, and in its simplest form, sediment genesis involves the transformation of a parent rock mass into a particulate end product by processes that include size reduction and selection during weathering, transportation, and deposition. The many variables that operate simultaneously during this transformation can be shown to produce a distribution of particle sizes that approaches asymptotically the lognormal form when the effect of the variables is multiplicative. This was first shown by Kolmogorov (1941). Currently available models combine breakage and selection in differing degrees, but are similar in treating the processes as having multiplicative effects on particle sizes. The present paper, based on careful specification of the initial state, the nth breakage rule and the nth selection rule, leads to two stochastic models for particle breakage, and for both models the probability distributions of particle sizes are obtained. No attempt is made to apply these models to real world sedimentary processes, although this topic is touched upon in the closing remarks. 相似文献
16.
针对广西盘龙铅锌矿选矿厂铅浮选指标较差的现状,以现场产出的铅中矿1为研究对象,采用化学多元素分析、物相分析、光学显微镜鉴定、解离度统计等技术手段,对盘龙铅锌矿浮选铅中矿的化学组成、物相组成、目的矿物的嵌布粒度及嵌布特征进行了详尽的工艺矿物学特征研究。研究结果表明,铅中矿1含Pb 2. 03%,主要赋存于方铅矿中;方铅矿整体嵌布粒径细小,经筛分分级后,不同粒径的分级产品中方铅矿的嵌布特征差异性极大,+74μm及-74～+39μm部分含铅矿物颗粒基本为铅-锌-硫复杂连生的集合体,这两个粒级金属总占有率达56%以上,是影响盘龙铅锌矿铅浮选指标的关键所在。根据以上研究结果,推荐采用对铅中矿1进行分级磨矿工艺流程改造,提高铅中矿1中方铅矿的单体解离度,实现铅精矿中铅金属回收率的进一步提升。 相似文献
17.
Farooq Azam Grieg F. Steward David C. Smith Hugh W. Ducklow 《Journal of Earth System Science》1994,103(2):341-351
In the Arabian Sea, temporal contiguity of highly oligotrophic and eutrophic periods, along with high water temperatures,
may result in unique features of bacteriaorganic matter coupling, nutrient cycling and sedimentation, which are unlike those
in the classical oligotrophic and eutrophic waters. Bacteria-phytoplankton interactions are suggested to influence phytoplankton
aggregation and its timing. It is also hypothesized that, within aggregates, hydrolytic ectoenzyme activity, together with
condensation reactions between the hydrolysis products, produce molecular species which are not readily degraded by pelagic
bacteria. Accumulation of a reservoir of such slow-to-degrade dissolved organic carbon (DOC) is proposed to be a carbon flux
and energy buffer, which moderates the response of bacteria to the dramatic variations in primary production in the Arabian
Sea. Use of the slow-to-degrade DOC pool during the intermonsoon could temporarily render the Arabian Sea net-heterotrophic
and a source of CO2 to the atmosphere. Stored DOC is also suggested to balance the observed deficit between mesopelagic carbon demand and the
sinking particulate organic carbon supply. Knowledge of the significance of bacteria in carbon storage and cycling in the
Arabian Sea is needed to understand the response of the ocean’s biogeochemical state to strong physical forcing and climate
change. 相似文献
18.
Sediments often occur as non‐normal size distributions composed of discrete, partially aggregated particle populations. These populations reflect provenance, dispersal pathways and their depositional environments. Recent experimental laboratory studies describing mud flocculation in turbulent marine systems prompted this investigation of the potential of aggregates to record size‐sensitive transport dynamics in a terrestrial fluvial system. Here, sediment‐size distributions in their natural condition of particle–aggregate mixtures are analysed by parametric statistics. A practical and freely available decompositional approach is outlined and field tested, which allows sediment to be viewed in both its conventional particulate form and as its naturally occurring mixture of transport‐stable aggregates and elementary particles. From a sequence of upward‐fining slack water couplets in the Flinders Ranges, South Australia, it is demonstrated that the characteristics, provenance and depositional history of fine‐grained sediments consisting of particle‐aggregate mixtures can best be understood fully by quantifying aggregation. 相似文献
19.
采用淘析法、激光粒度分析法、渗透过滤法、显微镜法对膨润土及石英的粒度进行测量比较分析。实验结果表明：4种方法得到的粒度由大到小依次为淘析法、激光粒度分析法、显微镜法、渗透过滤法;由于凝聚的影响,淘析法与激光粒度分析法测试结果粒度偏大;渗透法分析结果与显微镜法结果较为接近;膨润土在水中崩解的粒度比石英要小,但采用沉降法分离提纯,膨润土比石英更易于团聚,因此在湿法提纯研究中,有必要添加分散剂。 相似文献
20.
David M. Cwiertny Robert M. Handler Vicki H. Grassian 《Geochimica et cosmochimica acta》2008,72(5):1365-1380
The Fe(II)/Fe(III) redox couple plays an important role in both the subsurface fate and transport of groundwater pollutants and the global cycling of carbon and nitrogen in iron-limited marine environments. Iron oxide particles involved in these redox processes exhibit broad size distributions, and the recent demonstrations of dramatic nanoscale size-effects with various metal oxides has compelled us, as well as many others, to consider whether the rate and extent of Fe(II)/Fe(III) cycling depends upon oxide particle size in natural systems. Here, we investigated the reaction of Fe(II) with three different goethite particle sizes in pH 7.5 suspensions. Acicular goethite rods with primary particle dimensions ranging from 7 by 80 nm to 25 by 670 nm were studied. Similar behavior with respect to Fe(II) sorption, electron transfer and nitrobenzene reduction was observed on a mass-normalized basis despite almost a threefold difference in goethite specific surface areas. Scanning electron microscopy (SEM) images, dynamic light scattering (DLS) and sedimentation measurements all indicated that, at pH 7.5, significant aggregation occurred with all three sizes of goethite particles. SEM images further revealed that nanoscale particles formed dense aggregates on the order of several microns in diameter. The clear formation of particle aggregates in solution raises questions regarding the use of primary particle surface area as a basis for assessing nanoscale size-effects in iron oxide suspensions at circum-neutral pH values. In our case, normalizing the Fe(II) sorption densities and rate constants for nitrobenzene reduction by BET surface area implies that goethite nanoparticles are less reactive than larger particles. We suspect, however, that aggregation is responsible for this observed size-dependence, and argue that BET values should not be used to assess differences in surface site density or intrinsic surface reactivity in aggregated particle suspensions. In order to realistically assess nanoscale size-effects in environmentally relevant systems that are likely to aggregate, new methods are needed to quantify the amount of surface area accessible for sorption and reaction in wet nanoparticle suspensions, rather than assuming that this value is equivalent to the surface area determined from the characterization of dry nanoparticles. 相似文献