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排序方式: 共有146条查询结果,搜索用时 31 毫秒
31.
Ole F.?ChristensenEmail author G.?Cassiani P. J.?Diggle P. Ribeiro?Jr G.?Andreotti 《Stochastic Environmental Research and Risk Assessment (SERRA)》2004,18(5):339-350
Using monitored natural attenuation is an increasingly popular strategy for dealing with contaminated aquifers. This paper provides a statistical methodology for the estimation of the relative efficiency of natural attenuation mechanisms. The methodology provides estimates, with associated measures of uncertainty, of the relative efficiency of four types of bio-degradation (oxidation using oxygen as the electron-acceptor, denitrification, iron reduction and sulfate reduction). A data set from Trecate, Italy, is analysed using the methodology. The analysis shows that sulfate is the main cause of hydrocarbon removal on this site. It is also seen that oxidation using oxygen seems to be more preferential than the other reactions, in the sense that this reaction is relatively more efficient than other reactions at locations where the hydrocarbon concentration is low. 相似文献
32.
Souad Boubekraoui Michel Courteaud Maurice Aubert Yves Albouy Jean Coudray 《Journal of Applied Geophysics》1998,40(4):165-177
In order to investigate aquifers, several geophysical surveys have been carried out in the Baril area of the southern flank of Piton de la Fournaise volcano on Reunion in the Indian Ocean using audiomagnetotelluric (AMT), very-low-frequency (VLF) and self-potential (SP) methods. We present the results with emphasis on a comparison between SP data and the findings of geoelectric surveys. AMT soundings have indicated, from the surface downward, three layers: (i) resistive volcanic rocks, (ii) an intermediate resistivity layer, and (iii) a conductive basement attributed to a seawater-bearing aquifer. VLF measurements allow the mapping of the first layer apparent resistivity, and therefore its bottom, when the true resistivity is supposed to be isotropic and homogenous. When this assumption does not hold, only the SP method permits the mapping of this bottom. Because of the good agreement between the SP and electromagnetic results, we propose the SP method as the first tool that should be used in studying shallow hydrogeological structures in volcanic areas. 相似文献
33.
张举兼 《地质灾害与环境保护》1997,8(3):6-12
从地形地貌,气候特征和地表水三方面简述了珠海市的自然地理概况,论核实 珠海市基础地 中的地层,岩层分布情况以及构造特征。重点对珠海市地下水的类型,形成,赋存条件,水理性质,以及岩土的居因类型,分布规律,海岸类型和工程地质特征等作了初探讨 相似文献
34.
现代城市中景观湖建设日益增多,尤其北方各大城市已建或在建橡胶坝工程较多,由此引起的湖区水文地质条件危害问题也日益突出。工程应用中多采用水位外推延伸法来对其危害进行估算。根据蓄水后沿岸水文地质条件,采用数学建模方法进行预测评价,通过对湖区相对隔水层的确定、水文地质条件模型的建立等步骤,最后得出湖区浸没危害的预测评价结果。 相似文献
35.
对哈萨克斯坦,吉尔吉斯斯坦两国地下流体资料的初步分析 总被引:11,自引:4,他引:7
依据来自哈萨克斯坦,吉尔吉斯斯坦两国地下流体的交换资料,分析了它们对天山及其邻区强震的映震特征,认为:(1)水化学异常时间与水动态异常的时间不同;(2)气体,离子,水动态异常形态多样;(3)水化学正负正常不确定;(4)异常幅度变化复杂;(5)强震远场效应明显;(6)震后效应显著并具有不可逆性。 相似文献
36.
E. G. Drozhko Y. U. Glagolenko Y. G. Mokrov G. A. Postovalova L. M. Samsonova A. V. Glagolev S. A. Ter-Saakian M. L. Glinsky N. A. Vasil'kova A. V. Skokov H. A. Wollenberg C.-F. Tsang W. Frangos R. D. Solbau K. A. Stevenson W. M. Lowder M. G. Foley 《Environmental Geology》1997,29(3-4):216-227
In September 1994, a Russian-American team conducted hydrogeological, geochemical, geophysical, and radiometric measurements
in the territory of the Mayak Production Association, Russia. The primary purpose of these operations was to examine the frontal
area of a radioelement- and nitrate-laden groundwater plume moving from the disposal site, Lake Karachai, toward the Mishelyak
River. Activities encompassed (1) isolation of hydrologic intervals in two wells and production of water from these intervals,
to compare isolated versus open-well sampling methods and to determine hydraulic transmissivities of the aquifer(s); (2) surface
and soil-water sampling, accompanying radiometric measurements and subsequent chemical analyses; and (3) electrical resistivity
profiling in areas of expected contrasting resistivity.
Preliminary results indicate that (1) 60Co, 137Cs, and 90Sr are present in small concentrations (∼0.1% of permissible levels) in water of the Mishelyak River; (2) analyses of water
samples collected by a downhole sampler and of water produced from packed-off intervals agree within limits of laboratory
accuracy, attesting to the efficacy of the sampling methods presently used by the Russian workers; (3) considerable differences
in contaminant concentrations exist between nearby wells, supporting the concept that the plume from Lake Karachai toward
the Mishelyak River is controlled by steeply dipping fractures and shear zones; and (4) strong contrasts occur between the
electrical resistivities of soil and bedrock.
Further collaborative work is strongly recommended and should include more detailed isolation of intervals in wells by multi-packer
installations, to better determine the geochemical and hydrological characteristics of the Karachai-Mishelyak system; deployment
of a broader soil water and soil sampling array; a more detailed examination of the distribution and concentration of radionuclides
by high-resolution field gamma spectrometry; and a detailing of the area's electrical resistivity setting, using a mobile
electromagnetic measurement system.
Received: 22 January 1996 · Accepted: 1 April 1996 相似文献
37.
The currently inactive deep-seated gravitational slope deformation (DGSD) Sagspitz in Tyrol, Austria, covers an area of 3 km2 and originated along a glacially over-steepened slope composed mainly of phyllites belonging to the Innsbruck Quartzphyllite
Complex. Past mass movement processes caused the formation of fracture systems and slump bodies which consequently form the
aquifers of relatively large springs in a rock type with generally very low permeability and poor porosity. Analysis of water
chemistry, oxygen isotope, and field parameters of the springs emerging from the DGSD imply that multilevel aquifers exist
and enabled the detection of continuous deep flow paths through the entire length of the mass movement from the main scarp
to the toe of the slope. It is shown that the aquifer boundaries and spring emergences throughout the loosened rock mass can
be correlated to the internal and basal shear zones of the DGSD so that this hydrogeological approach proved to be useful
for evaluating the mass movement structure. 相似文献
38.
39.
Photogeological, geoelectrical, and drill-hole data were used to determine the hydrogeological conditions of the regolith layer mantling the Precambrian rocks in the northern Obudu plateau of southern Nigeria. The regolith thickness is 3.8–89.5 m (mean 38 m). Water for domestic purposes is extracted by dug wells <15 m deep and shallow boreholes <50 m. The mean value for permeability of the saturated regolith is 7.5×10–1 m/d and for transmissivity, 3.8×10–1 m2/d. The regolith wells have a high specific capacity, 40–270 m3/d/m and a high yield, 700–4,050 m3/d. Using statistical analysis, well yields and specific capacities can be estimated if the saturated thickness and apparent resistivity of regolith layers are known from drill-hole data and vertical electrical sounding. Chemical data show that the major groundwater types are calcium-bicarbonate (Ca-HCO3) and sodium+potassium bicarbonate [(Na+K)-HCO3] and the water quality meets national and international standards for drinking, domestic and agricultural purposes. However, for future proper management of water resources in the area, care should be taken, that waste-disposal sites for both solid and human waste should not be located near waste sources.
Resumen Se utilizaron datos fotogeológicos, geoeléctricas y de barrenación para determinar las condiciones hidrogeológicas de la capa de regolito que cubre rocas precámbricas en la meseta obudu septentrional del sur de Nigeria. El regolito tiene un espesor de 3.8–89.5 m (promedio38m). El agua para uso doméstico se extrae medio de pozos excavados hasta profundidades de 15 metros y por barrenos no muy profundos de 50 metros. La permeabilidad promedio del regolito saturado es 7.5×10–1 m/d, con transmisibilidad de 3.8×10–1 m2/d. Los pozos dentro del regolito tienen alta capacidad específica de 40–270 mm2/d/m y un alto rendimiento de 700–4,050 mm3/d. Se puede estimar el rendimiento de los pozos y capacidades específicas usando análisis estadístico si el espesor saturado y la resistividad aparente de las capas de regolito se conocen a partir de los datos de barrenación y sondeo geoeléctrico. Los datos químicos muestran que los tipos de aguas subterráneas son principalmente de bicarbonato de calcio (Ca-HCO3) y bicarbonato de sodio y potasio [(Na+K)-HCO3] y el agua cumple las estándares de calidad nacional y internacional para agua potable y para uso doméstico y agrícola. Sin embargo para el futuro manejo apropriado del recurso de agua en el área es importante que se tenga cuidado de que los sitios de desechos de basura solida y humana no sean ubicados cerca de los fuentes de agua.
Résumé Des données photogéologiques, géoélectriques et de forage ont été utilisées afin de déterminer les conditions hydrogéologiques de laquifère régolithique qui recouvre les roches précambriennes dans le plateau nord dObudu au sud du Nigeria. Lépaisseur de régolithe varie entre 3.8 et 89.5 m avec une moyenne de 38 m. Leau destinée aux usages domestiques est extraite de puits de surface (< 15 m de profondeur) et de puits artésiens (< 50 m). La valeur moyenne de perméabilité du régolithe saturé est de 7.5×10–1 m/j et la transmissivité moyenne de 3.8×10–1 m2/j. Les puits qui exploitent laquifère de régolithe ont une capacité spécifique variant entre 40 et 270 m2/j/m et un rendement élevé de 700 à 4 500 m3/j. Avec laide dune analyse statistique, le rendement et la capacité spécifique des puits peuvent être estimés si lépaisseur saturée et la résistivité apparente des couches de régolithe sont déterminées avec des forages et des relevés électriques verticaux. Des données sur la composition chimique de leau montrent que les types deau majeurs sont bicarbonaté-calcique et bicarbonaté sodique + potassique et que la qualité de leau rencontre les standards nationaux et internationaux pour leau potable, lutilisation domestique et à fins dagriculture. Malgré tout, dans loptique dune gestion appropriée des ressources en eau dans la région, une attention particulière doit être portée aux sites denfouissement des déchets solides et humains qui ne devraient pas être localisés près des sources deau.相似文献
40.
Michele Spizzico 《Hydrogeology Journal》2005,13(3):493-505
High concentrations of 222Rn have been found throughout the waters of the coastal carbonate-rock Mesozoic aquifer located in the region of Apulia in southern Italy. Studies undertaken have determined that such concentrations are due to the radioisotopic features of terra rossa, a type of paleosol that is generated as a residual byproduct of carbonate dissolution and is found to be widespread throughout the aquifers fissures and karst cavities.These special types of soil feature a rather high clay content (80–95%) and, although variable, their specific 226Ra activity (70–147 Bq/kg) is nonetheless considerably greater than that of limestone (~50 Bq/kg). In fact, there are substantial differences in 222Rn concentrations found in waters that come into contact with this type of rock and paleosol.The partial dissolution of some carbonate rock samples in the laboratory confirmed that the 226Ra released by the dissolved rock primarily accumulates in the residual soil deposits, especially in ones containing finer granules. This has also been the result of experiments conducted on 15 terra rossa samples collected from the region, which indicates that there is a close correlation between the specific 226Ra activity and the clay content of such paleosols, which varies with the stage of weathering.It has been found that the 222Rn concentrations in the regions waters, depend on the specific terra rossa 226Ra activity rather than on the quantity of terra rossa.Field checks have confirmed the possibility of using 226Ra and 222Rn as natural tracers in order to define hydrogeological problems in special environments such as karst. They can be used to distinguish the different water bearing zones in the carbonate-rock aquifer; analyze the influence of tides on coastal springs; determine the flow direction in the proximity of a well; recognize, recharge and the progressive decline of the groundwater level; derive indications of underground flow paths; and the occurrence of fissures and karstic cavities in the carbonate-rock aquifer.
相似文献
Michele SpizzicoEmail: Phone: +39-080-5963676Fax: +39-080-5963675 |