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941.
942.
Massimo Angelone Carlo Cremisini Vincenzo Piscopo Marco Proposito Fabio Spaziani 《Hydrogeology Journal》2009,17(4):901-914
Arsenic occurrence in groundwater near the Cimino-Vico volcanoes (central Italy) was analysed considering the hydrostratigraphy and structural setting and the shallow and deep flows interacting within the Quaternary volcanics. Groundwater is the local source of drinking water. As documented in the past, arsenic in the groundwater has become a problem, and the European maximum allowable contaminant level was recently lowered to 10 μg/L. Chemical analyses of groundwater were conducted, sampled over an area of about 900 km2, from 65 wells and springs representative of the volcanic aquifer and thermal waters. Considering the type of aquifer, the nature of the aquifer formation and its substratum, the hydrochemical data highlight that the arsenic content of the groundwater is mainly connected with the hydrothermal processes in the volcanic area. Thermal waters (54–60°C) fed from deep-rising fluids show higher arsenic concentrations (176–371 μg/L). Cold waters sampled from the volcanic aquifer are characterized by a wide variability in their arsenic concentration (1.6–195 μg/L), and about 62% exceed the limit of 10 μg/L. Where the shallow volcanic aquifer is open to deep-rising thermal fluids, relatively high arsenic concentrations (20–100 μg/L) are found. This occurs close to areas of the more recent volcano-tectonic structures. 相似文献
943.
Characterization of salt-water intrusion in the lower Esino Valley, Italy using a three-dimensional numerical model 总被引:1,自引:0,他引:1
A seawater-intrusion study was conducted at an oil-refinery site located on the coast in the lower Esino Valley, Italy. A steady-state density-dependent flow model was used in order to understand the position of the freshwater/salt-water interface, as influenced by the hydrogeologic structure and the presence of industrial activities and a river. Collected data and model results showed that in a large part of the area, the salt-water interface is steep and can penetrate only a few meters inland. On the other hand, close to the river mouth, seawater represents the main saline source for the aquifer. The river, in connection with the sea, can enhance seawater encroachment into the coastal aquifer; a long-term survey of river level and chloride concentrations in groundwater is recommended to further improve the physical model and to obtain a better calibration. At the refinery site, two “secondary” sources of saline water were identified and were demonstrated to have had a great influence on the presence of brackish waters in the unconfined aquifer: leakage from the fire-extinguishing system (network of pipes containing seawater) and rough sea events. This confirmed that groundwater contamination by chloride can result from means other than seawater intrusion. 相似文献
944.
C-axis fabrics of quartz-ribbons during high-temperature deformation of syn-tectonic granitoids (Sila Massif, Calabria, Italy) 总被引:1,自引:0,他引:1
Late-Hercynian, high temperature (HT) shear deformation affected the zone straddling the contact between the Sila Massif batholith (above) and the host migmatitic paragneisses (below). A segment of the regional HT shear zone was investigated close to the town of Mesoraca, where a natural section allows one to analyse the solidus deformation of syn-tectonic granitoids. Shearing favoured the formation of polycrystalline quartz ribbons in deformed granodiorite and tonalite. Two main c-axis fabrics were found in the quartz-ribbons, different from each other by opening angles around Z between strong point maxima, in accordance with deformation under granulite to amphibolite facies conditions. These fabrics, along with microstructural observations, suggest that temperature of deformation played a key role and that ribboning was accompanied by the activation of (i) prism [c] slip and prism [c] + prism <a> slips, under granulite facies conditions, followed by (ii) basal <a> and prism <a> slips under amphibolite facies conditions. 相似文献
945.
效用问题是农业水资源利用的关键和核心.构建科学合理的指标体系评价农业水资源利用效用对于实现农业水资源持续高效利用有着重要的意义.国内外对水资源利用效用评价的理论和方法研究经历了由单一的用水效率评价向以效率和效益有机结合为特征的效用评价的发展历程,其评价尺度也从最初的作物或田间等微观尺度向灌区、流域、国家乃至全球等中观和宏观尺度发展.未来农业水资源利用效用评价研究发展的重点,将集中在建立基于不同尺度水平衡观点上的农业水资源利用效用评价指标体系以及不同尺度指标的尺度效应及转换等方面. 相似文献
946.
Affected by thermal perturbation due to mantle uprising,the rheological structure of the lithosphere could be modified,which could lead to different rifting patterns from shelf to slope in a passive continental margin.From the observed deformation style on the northern South China Sea and analogue modeling experiments,we find that the rift zone located on the shelf is characterized by half grabens or simple grabens controlled mainly by long faults with large vertical offset,supposed to be formed with normal lithasphere extension.On the slope,where the lithosphere is very hot due to mantle upwelling and heating,composite grabens composed of symmetric grabens developed.The boundary and inner faults are all short with small vertical offset.Between the zones with very hot and normal lithosphere,composite half grnbens composed of half grabens or asymmetric grabens formed,whose boundary faults are long with large vertical offset,while the inner faults are relatively short.Along with the thickness decrease of the brittle upper crust due to high temperature,the deformation becomes more sensitive to the shape of a pre-existing weakness zone and shows orientation variation along strike.When there was a bend in the pre-existing weakness zone,and the basal plate was pulled by a clockwise rotating stress,the strongest deformation always occurs along the middle segment and at the transition area from the middle to the eastern segments,which contributes to a hotter lithosphere in the middle segment,where the Baiyun (白云) sag formed. 相似文献
947.
基于高分辨率层序地层学的大庆长垣南部浅层气分布特征研究 总被引:1,自引:0,他引:1
松辽盆地大庆长垣南部黑帝庙油层具有良好的浅层气开发潜力。应用高分辨率层序地层学原理,通过对各级基准面旋回结构、叠加样式的沉积动力学分析,利用1164口测井曲线和6口井岩芯资料,把松辽盆地大庆长垣南部黑帝庙油层划分为1个长期基准面旋回、4个中期基准面旋回、25个短期基准面旋回,提出了研究区北部为后期构造抬升而缺失的层序地层新格架。短期基准面旋回内储层沉积特征及单砂体展布规律研究表明:黑帝庙油层为松辽盆地北部物源控制的湖盆逐渐萎缩背景下形成的河控缓坡三角洲前缘亚相沉积体系,微相类型以水下分流河道、河口坝和远砂坝为主。依据区域性湖侵成因的9套暗色泥岩盖层把黑帝庙油层垂向上划分为9套储盖组合;生储盖组合特征及动态资料综合分析表明浅层气主要分布于长期旋回下降早期的中期旋回下降晚期或上升早期储层砂体中;单砂体展布规律与气源断层和构造的合理匹配是浅层气富集的主控因素,气藏类型主要为构造—岩性、断层—岩性圈闭,在以上研究的基础上应用气水解释模板在全区预测地质储量,其研究对指导整个松辽盆地北部浅层气勘探与开发具有重要理论意义和实际应用价值。 相似文献
948.
陕西省数字地震台网与模拟地震台网地震参数比较 总被引:1,自引:1,他引:0
对1998年1月至2001年12月之间,陕西省数字地震台网与模拟地震台网测定的地震参数作了比较,并进行了讨论。 相似文献
949.
N. Elias-Rosa S. Benetti M. Turatto E. Cappellaro S. Valenti A. A. Arkharov J. E. Beckman A. Di Paola M. Dolci A. V. Filippenko R. J. Foley K. Krisciunas V. M. Larionov W. Li W. P. S. Meikle A. Pastorello G. Valentini W. Hillebrandt 《Monthly notices of the Royal Astronomical Society》2008,384(1):107-122
950.
河道砂体宽/窄方位三维观测系统地震物理模型分析 总被引:1,自引:0,他引:1
The effect of the wide and narrow azimuth 3D observation systems on seismic imaging precision is becoming a hot area for studies of high precision 3D seismic acquisition methods in recent years. In this paper we utilize 3D physical seismic modeling experiments. A 3D channel sand body physical seismic model is constructed and two acquisition systems are designed with wide azimuth (16 lines) and narrow azimuth (8 lines) to model 3D seismic data acquisition and processing seismic work flows. From analysis of migrated time slice data with high quality and small size, we conclude that when the overlying layers are smooth and lateral velocities have little change, both wide and narrow azimuth observation systems in 3D acquisition can be used for obtaining high precision imaging and equivalent resolution of the channel sand body. 相似文献