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861.
S. I. Mayr H. Burkhardt Yu. Popov A. Wittmann 《International Journal of Earth Sciences》2008,97(2):385-399
Internal surface, formation factor, Nuclear Magnetic Resonance (NMR)-T2 relaxation times and pore radius distributions were
measured on representative core samples for the estimation of hydraulic permeability. Permeability is estimated using various
versions of the classic Kozeny–Carman-equation (K–C) and a further development of K–C, the fractal PaRiS-model, taking into
account the internal surface. In addition to grain and pore size distribution, directly connected to permeability, internal
surface reflects the internal structure (“micro morphology”). Lithologies could be grouped with respect to differences in
internal surface. Most melt rich impact breccia lithologies exhibit large internal surfaces, while Tertiary post-impact sediments
and Cretaceous lithologies in displaced megablocks display smaller internal surfaces. Investigations with scanning electron
microscopy confirm the correlation between internal surface and micro morphology. In addition to different versions of K–C,
estimations by means of NMR, pore radius distributions and some gas permeability measurements serve for cross-checking and
calibration. In general, the different estimations from the independent methods and the measurements are in satisfactory accordance.
For Tertiary limestones and Suevites bulk with very high porosities (up to 35%) permeabilites between 10−14 and 10−16 m2 are found, whereas in lower Suevite, Cretaceous anhydrites and dolomites, bulk permeabilites are between 10−15 and 10−23 m2. 相似文献
862.
Hydrogeologic assessment of escalating groundwater exploitation in the Indus Basin, Pakistan 总被引:1,自引:1,他引:0
Groundwater development has contributed significantly to food security and reduction in poverty in Pakistan. Due to rapid population growth there has been a dramatic increase in the intensity of groundwater exploitation leading to declining water tables and deteriorating groundwater quality. In such prevailing conditions, the hydrogeological appraisal of escalating groundwater exploitation has become of paramount importance. Keeping this in view, a surface water–groundwater quantity and quality model was developed to assess future groundwater trends in the Rechna Doab (RD), a sub-catchment of the Indus River Basin. Scenario analysis shows that if dry conditions persist, there will be an overall decline in groundwater levels of around 10 m for the whole of RD during the next 25 years. The lower parts of RD with limited surface water supplies will undergo the highest decline in groundwater levels (10 to 20 m), which will make groundwater pumping very expensive for farmers. There is a high risk of groundwater salinization due to vertical upconing and lateral movement of highly saline groundwater into the fresh shallow aquifers in the upper parts of RD. If groundwater pumping is allowed to increase at the current rate, there will be an overall decline in groundwater salinity for the lower and middle parts of RD because of enhanced river leakage. 相似文献
863.
Point scale studies in different settings of glacial geology show a large local variation of redox conditions. There is a need to develop an upscaling methodology for catchment scale models. This paper describes a study of field-scale heterogeneity of redox-interfaces in a till aquitard within an area of 600?×?600 m. The results showed significant variation of the depths to the redox-interface and thickness of the aquitard. Nitrate was present above the redox-interface but reduced to non-detectable levels a few metres below the interface. An upscaling approach for an area of 92 km2 is proposed. Two models are proposed to predict the depth to the redox-interface in the aquitard and the resulting nitrate recharge concentrations to an underlying aquifer. The first model assumes that the depth to the redox-interface reflects the hydraulic head in the aquitard, and the second model assumes that the depth of the redox-interface is randomly distributed according to a log-normal probability distribution function. The upscaling approach using the random redox model estimated recharge concentrations comparable to the observed concentration in the underlying aquifer. The presented upscaling approach is applicable in distributed catchment models where sub-grid variability cannot be represented by the large grids. 相似文献
864.
865.
Nathan S. Hall R. Wayne Litaker Elizabeth Fensin Jason E. Adolf Holly A. Bowers Allen R. Place Hans W. Paerl 《Estuaries and Coasts》2008,31(2):402-418
A dense bloom of the ichthyotoxic dinoflagellate Karlodinium veneficum was discovered in the Neuse River Estuary, North Carolina, on 19 October 2006 and was associated with four subsequent fish
kills. Microscopic, photopigment, DNA, and toxicological techniques confirmed bloom identity and toxicity. High-resolution
spatio-temporal data from ship-board and fixed automated sampling stations provided a unique opportunity to investigate the
environmental conditions that initiated, maintained, and terminated the K. veneficum bloom. Bloom initiation and growth were favored by high nutrient availability and reduced dispersal during the period of
declining riverine discharge after Tropical Storm Ernesto. K. veneficum out-competed other co-occurring dinoflagellates, perhaps because of the production of karlotoxins that are known to act as
grazing deterrents and to facilitate mixotrophic feeding. Once the bloom was established, small-scale hydrodynamic processes,
coupled with vertical migration, concentrated cells along a frontal convergence to high densities (>200,000 cells per milliliter).
By 26 October 2006, wind mixing and possible nutrient stress disrupted the bloom. Release of cell-bound toxins during the
bloom collapse likely accounted for the associated fish kill events where fish were reported as exhibiting typical symptoms
of karlotoxin poisoning. The dynamics of this bloom underscore the tight control of harmful algal blooms by meteorological
forcing, hydrology, and sediment nutrient input in this shallow lagoonal estuary. 相似文献
866.
This paper presents an application of rock engineering system (RES) in an attempt to reveal and assess the inherent instability
potential of 388 sites where equivalent landslides have been manifested and recorded in the region of Karditsa County, Greece.
The main objective has been defining the principal causative and triggering factors responsible for the manifestation of landslide
phenomena, quantify their interactions, obtain their weighted coefficients, and calculate the instability index, which refers
to the inherent potential instability of each natural slope of the examined region. From the statistical interpretation of
the data reported in a well-documented database and concerning the examined failure sites, a clear correlation between the
instability index and the area affected by a single landslide event has been revealed. Almost the entire failure sites, 98%
of the examined slope sites, exhibit an instability index value over 55, a value which is thought to be a critical threshold
for landslide manifestation concerning natural slopes in Karditsa County. It is argued that the presented RES methodology,
engaging the selected set of parameters, could be considered as an effective expert's tool for ranking, in an objectively
optimal and simple way, the instability potential of natural slopes in Karditsa County, and thus providing a tool for sound
zoning landslide hazard. 相似文献
867.
868.
Assessment of cement’s dust impact on the soil using principal component analysis and GIS 总被引:2,自引:1,他引:1
Z. Zerrouqi M. Sbaa Ph.D. M. Oujidi Ph.D. M. Elkharmouz S. Bengamra A. Zerrouqi 《International Journal of Environmental Science and Technology》2008,5(1):125-134
To evaluate the impact of the cement’s dust emitted by the eastern Moroccan cement factory (Oujda Holcim) and deposited on the soil of the Ain Lahjar commune, 58 samples of soil were collected around the factory on a radius of 3 km approximately. The physicochemical analyses of the upper 3 cm of the soil surface samples correspond to the pH, electrical conductivity, the chlorides and the oxides of Ca, Al, Fe, K, Mn, S and Si which were analyzed by the fluorescence of X-rays. The preliminary results demonstrate that this dust are especially basic and contain a high free lime (43% CaO). The principal component analysis (applied on the 58 samples of soil) allows deducting that the free lime and the sulfur oxide are the tracer elements of this form of pollution. Furthermore, the spatial projection of the factor scores of the principal component analysis using the geographical information system permits to determine the spatial distribution of more polluted areas of soils as well as to estimate their surface (63.3% of the survey zone). 相似文献
869.
Transient and spatial modeling and simulation of polybrominated diphenyl ethers reaction and transport in air, water and soil 总被引:1,自引:0,他引:1
M. Mousavi Ph.D. S. Kiani S. Lotfi N. Naeemi M. Honarmand 《International Journal of Environmental Science and Technology》2008,5(3):323-330
The release of the wastes containing polybrominated diphenyl ethers into the environment is a worldwide major concern. Investigation of spatial and temporal variations of polybrominated diphenyl ethers concentrations due to different factors, especially the transport of these species between air and water as well as between air and soil is the purpose of present research. A model was developed and solved using the methods of finite difference and lines. Simulations were implemented for three dimensions of width, length, and height and also time for the air compartment, whereas for the soil and water compartments, variations were considered only with respect to height and time. Transport between water and soil was disregarded for simplicity at this stage. Vancouver’s landfill was considered as a case study. Lower concentrations in air and higher concentrations in water at the interface show that these pollutants tend to diffuse from air to water. Concentrations of all four pollutants decrease near the interface in soil as time passes, but they are predicted to be almost constant at other levels. 相似文献
870.
Ability of indigenous Bacillus licheniformis and Bacillus subtilis in microbial enhanced oil recovery 总被引:1,自引:1,他引:0
S. Haghighat A. Akhavan Sepahy Ph.D. M. Mazaheri Assadi Ph.D. H. Pasdar Ph.D. 《International Journal of Environmental Science and Technology》2008,5(3):385-390
Microbially produced lipopeptide have been isolated and studied for microbial enhanced oil recovery. About 60 gram positive bacteria isolated from soil contaminated with crude oil, near the crude oil storage tank in Tehran Refinery, Tehran, Iran. However, most of these studies have produced lipopeptide by one of the pure-culture microbes isolated in a laboratory. Among the isolates, heamolytic tests revealed two biosurfactant producers. The isolated strains were designated as C2, E1. By using morphological, biochemical and molecular biology tests (16 SrRNA), the strains identified as Bacillus licheniformis and Bacillus subtitlis, respectively. Emulsification activity and measurement of surface tension indicated that, the isolates were high producers of biosurfactant. The product of C2 and E1 is mainly lipopeptide. This product reduce surface tension from 65 to 30 mN/m. Emulsified activity of crude oil was 92% for C2 and 90 % in case of E1. This is the first report of indigenous Bacillus licheniformis and Bacillus subtilis from a soil contaminated with oil in an Iranian refinery with ability to produce biosurfactant. 相似文献