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1.
《Journal of Geochemical Exploration》2004,81(1-3):59-70
This study deals with the experimental determination of the rate of weathering and As release from Au-bearing sulfide ores of the Mokrsko-West deposit (Czech Republic). The elevated As contents in the ore and the possible As mobilisation must be taken into account due to the close proximity of the deposit to the Vltava River, a source of drinking water for Prague. Crushed and homogenized ore material was divided into four grain-size fractions showing uniform chemical and mineralogical composition and subjected to batch and column leaching experiments. The most important reactions controlling metal leaching include (i) oxidation of sulfides, (ii) carbonate equilibrium and (iii) precipitation of hydrated ferric oxides (HFO). Hydrated ferric oxides were found to be important sorbents of mobilized As. The highest concentration of As in the leachates was obtained from the 64–1000 μm fraction. The oxidation rate in the agitated batch experiment calculated on the basis of sulfate concentrations is an order of magnitude higher (3.8×10−9 to 4.4×10−8 mol SO42− h−1 g−1) than in the static column experiment (9.6×10−10 to 7.4×10−9 mol SO42− h−1 g−1). The higher oxidation rate of batch experiments is explained by abrasion of oxidation products (mainly HFO) and by further exposition of reaction surfaces of the sulfide grains. 相似文献
2.
A multi-layered aquifer, typical of riverbank alluvial deposits in Korea, was studied to determine the hydrologic properties.
The geologic logging showed that the subsurface of the study site was comprised of four distinctive hydrogeologic units: silt,
sand, highly weathered and fresh bedrock layers. The electrical resistivity survey supplied information on lateral extension
of hydrogeologic strata only partially identified by a limited number of the geologic loggings. The laboratory column tracer
test for the recovered core of the sand layer resulted in a hydraulic conductivity of 5.00×10−2 cm/s. The slug tests performed in the weathered rock layer yielded hydraulic conductivities of 4.32–7.72×10−4 cm/s. Hydraulic conductivities for the sand layer calculated from the breakthrough curves of bromide ranged between 2.08×10−3 and 2.44×10−2 cm/s with a geometric mean of 6.89×10−3 cm/s, which is 7 times smaller than that from the laboratory column experiment. The trend of increasing hydraulic conductivity
with an increase in tracer travel length is likely a result of the increased likelihood of encountering a high conductivity
zone as more of the aquifer is tested. The combined hydrogeologic site characterization using hydraulic tests, tracer tests,
and column test with geologic loggings and geophysical survey greatly enhanced the understanding of the hydrologic properties
of the multi-layered alluvial aquifer. 相似文献
3.
Raw and retorted spent oil shales from Kentucky, as well as soil and overburden materials, were subjected to laboratory and field leaching tests. Standard batch leaching tests grossly undervalue the amount of dissolved ions as measured in the field, being too brief to enable slow reactions of the mineral matrix, such as hydrolysis and oxidation of sulfides or reactions of acidic leachates with soluble components of the clays. Laboratory column tests, devised to closely simulate natural leaching processes, achieved concentration levels and elemental release patterns similar to those found in field tests. The column tests provide a reliable means to assess the leachability of metals in these materials. 相似文献
4.
Partitioning of heavy metals on soil samples from column tests 总被引：3，自引：0，他引：3
R. N. Yong W. Z. W. Yaacob S. P. Bentley C. Harris B. K. Tan 《Engineering Geology》2001,60(1-4):307-322
In this study, column tests were used to determine the retention capability of three types of estuarine alluvia collected adjacent to landfill sites in South Wales. Selective sequential extraction (SSE) was used to study the retention mechanisms of heavy metals in the soil columns obtained from leaching experiments. Acid digestion was later used to check the validity of the SSE results. Breakthrough curves show good retention of heavy metal ions (Pb, Cu, and Zn) by all soils, where almost 99% of heavy metals were retained with the Ce/Co values in the order of 10−3. The retention strength of these soils was observed to be constant up to five pore volumes (PV). This corresponds with the pH of the effluents and pore water of soil slices, which also show good buffering capacity against very acidic leachate up to 5PV. The heavy metal extraction profiles from SSE show very similar trends with the retention profiles from the leaching experiments, where heavy metals were retained mainly at the top part where the leachate entered the column. SSE indicates qualitatively that heavy metals precipitated with carbonates and amorphous materials (oxides/hydroxides) are higher than heavy metal retention via exchangeable mechanisms. The mass balance calculation gives range of deviation of 1–16% of the total soil extraction. The distribution of the heavy metals with various soil constituents are ranked in the following order: Carbonates>Amorphous oxides hydroxides>Organic matter>Exchangeable phases. 相似文献
5.
基于标准大气定律和大气圆柱体分布模型,本文引进了大气重力格林函数,用离散格积方法求得了大气对重力场观测的影响,对台站高程、周围地形和地表温度变化等因素的影响问题进行了讨论．结果说明台站近区气压变化是大气重力信号的主要贡献者,考虑大气质量负荷引起的弹性地球形变效应后,对距台站0．5°的区域积分获得的大气重力导纳值为-0．3603μGal／hPa,占全球大气变化引起的总信号的90％以上,这一理论模型结果与超导重力仪实测结果相吻合,并能较有效地用于消除重力观测中的气压干扰成分． 相似文献
6.
We have performed an analysis of ESO Very Large Telescope (VLT) observations of Titan at 2 μm. The data were acquired with the Nasmyth Adaptative Optics System Near-Infrared Imager and Spectrograph (NAOS/CONICA), on the 16th of January 2005, that is 2 days after the landing of the Huygens probe (Hirtzig et al., 2007). The data consist in 21 spectra taken along two diameters of Titan’s disk at wavelengths between 2.03 and 2.5 μm. This range covers a part of the 2 μm methane window and the adjacent band. The data received a preliminary analysis in a recent paper (Negrão et al., 2007), essentially focused on the surface albedo near Huygens landing site. In this work, we perform an in-depth analysis to retrieve information about several aspects: the latitude haze distribution in the stratosphere and in the low atmosphere, the latitudinal variation of the surface albedo and its spectral behaviour. Also, this analysis allowed us to make sensitivity tests on the influence of the scatterer profiles on the retrieved surface albedo and its spectral slope. The news analysis confirms that, as was the case with VIMS observations at the same epoch, the Northern (currently winter) Hemisphere contains more haze than the southern one (Summer Hemisphere). The sensitivity tests show that the scatterer profiles have just a little impact on the surface albedo and its spectral slope. The analysis seems to confirm the presence of H2O and CH4 ices. 相似文献
7.
Nutrient distributions across the Porcupine Bank 总被引：1，自引：0，他引：1
8.
Vertical transport of selected polycyclic aromatic hydrocarbons (PAHs) in different particle-size fractions of sandy soils
was investigated by simulation experiments in soil columns. Tested soil samples were fractionized into three particle-sizes
including sand, coarse silt and fine silt (2,000–50, 50–20 and <20 μm). Rainfall simulations were conducted in artificially
PAHs contaminated soil columns with 30 cm length and 5 cm diameter in 40 days. PAHs were extracted from soil samples and determined
by high performance liquid chromatography (HPLC). Results showed that the residue level of PAHs in fine silt fraction reached
35.85 mg/kg, which was significantly higher than those in sand and coarse silt fraction (16.28 and 11.80 mg/kg, respectively),
probably because PAHs in macroporous fractions were prone to volatilize or degrade compared with that in microporous fractions.
Linear relationship between the residue levels of individual PAH (R
PAHs) and the value of partition coefficient (log K
oc) was regressed as R
PAHs = 1.55 × log K
oc − 5.86, R
2 = 0.91, n = 9. These results indicated that vertical transport of the mixed PAHs in soils were controlled both by the nature of PAHs
(i.e. log K
oc, molecular weight), soil particle size and soil organic contents, which could influence the transport of PAHs. 相似文献
9.
应力法和刚度法是判别土层液化的两种重要方法。本文在简要介绍判别原理的基础上,对两者作了比较,並结合工程实例和饱和标准砂样进行了对比。在相同的条件下,两种方法分析所得的抗液化安全系数是不相同的。本文提出的结论,就如何正确应用这二种方法提供了依据。 相似文献
10.
It has been widely accepted that reinforcement made of polyethylene and polypropylene is susceptible to creep and soil’s hydraulic conductivity varies with its void ratio. However, unfortunately there is no available sensitivity analysis on time-dependent embankment behaviour taking either reinforcement viscosity or time varying hydraulic conductivity of subsoil into consideration. The influence of geosynthetic reinforcement viscosity and decreasing hydraulic conductivity with consolidation on the time-dependent performance of embankments with floating columns is investigated using a fully 3D coupled model. For an embankment at the working height corresponding to a post-consolidation polypropylene geotextile strain of about 5%, it is shown that the assumption of constant hydraulic conductivity and the failure to consider the viscous behaviour of geosynthetic reinforcement can underestimate time-dependent embankment deformations (including differential crest settlement and horizontal toe movement). The effects of factors including the foundation soil, reinforcement stiffness, column stiffness, column spacing, column type (floating and fully penetrating), and construction rate, on the time-dependent behaviour of column supported embankments are explored. 相似文献