Delineation of three-dimensional well capture zones for complex multi-aquifer systems   总被引：10，自引：0，他引：10  

Frind EO  Muhammad DS  Molson JW 《Ground water》2002,40(6):586-598

The delineation of well capture zones is a basic component of ground water protection. The conventional methodology for capture zone delineation is backward advective particle tracking, often applied under the assumption of a two-dimensional aquifer. The suitability of the conventional approach for complex heterogeneous multi-aquifer systems was investigated, using the Waterloo Moraine aquifer system as an example. It was found that the conventional approach produces irregular particle tracks that require judgment to interpret in a meaningful way, and it can raise questions that may affect the credibility of the capture zone delineation. As an alternative, the potentially powerful but little-used backward-in-time advective-dispersive transport approach was investigated. A key advantage of this approach is its capability to represent local heterogeneities through the dispersion term. The dispersion process has a natural smoothing effect that results in unambiguous capture zones without the need for interpretation, thus enhancing credibility. The question of capture zone validation is also addressed. The meaning of a three-dimensional capture zone is considered, and it is shown that a fully three-dimensional representation of the system is crucial for valid results. The distinction between the maximum extent capture zone and the surface capture zone is also explained. In the case of complex heterogeneous systems, advective particle tracking can be used as an initial screening tool, whereas the more realistic backward-transport modeling approach can be used for final capture-zone delineation.  相似文献   

Carbonates, granulometry, and color of tills on the south-central Canadian Shield and their implications for stratigraphy and radiocarbon dating     

PAUL F. KARROW 《Boreas: An International Journal of Quaternary Research》1992,21(4):379-391

Till containing over 10% matrix carbonate extends in a belt 200–300 km wide south of the Hudson Bay Paleozoic basin source. The southern boundary is represented by the 'carbonate line', extending from Wawa to near Timmins and Cochrane in the study area. Higher silt content and lighter color are associated with the higher carbonate till. The carbonate tine corresponds approximately to the Chapleau moraine and correlative moraines to the northwest and may signify a discrete stratigraphic unit (possibly identifiable with the Matheson Till) formed by a glacial readvance. Glaciolacustrine sediments have higher carbonate content than nearby till and similarly form widespread sediment blankets even beyond that of the carbonate-rich till. Radiocarbon dating of amorphous organic sediments may be at risk because of old carbon error on such terrain and there may be some risk even in areas of much smaller carbonate content. A greater effort should be made to establish chronologies based on terrestrial plant matter, now more often possible with AMS radiocarbon dating.  相似文献   

Molecules and dust in circumstellar shells     

W. W. Duley 《Astrophysics and Space Science》1995,224(1-2):217-221

Circumstellar shells provide a unique environment for the study of dust formation and the relation of dust composition to specific atomic and molecular components. As a specific example, the formation of carbonaceous dust is discussed in relation to the presence of polycyclic aromatic hydrocarbon molecules and their survival in the interstellar medium. Some conclusions will be drawn concerning the composition of carbonaceous dust in circumstellar sources and that in the diffuse interstellar medium.  相似文献   

Vivianite auto-oxidation     

Allen R. Pratt 《Physics and Chemistry of Minerals》1997,25(1):24-27

Vivianite, Fe₃(PO₄)₂×8?H₂O, (010) surfaces cleaved in an N₂ gas atmosphere are examined using X-ray photoelectron spectroscopy (XPS). Quantitative evaluation of Fe(2p ₃₂) and O(1s) spectra show cleaved surfaces are partly oxidized. Ferric hydroxide is identified as an oxidation product. An auto-reduction-oxidation mechanism involving rupture of hydrogen bonds between the H₂O ligands which hold together the sheet structure of vivianite is proposed.  相似文献   

Seawater intrusion in continuous coastal aquifer-aquitard systems     

Emil O. Frind 《Advances in water resources》1982,5(2):89-97

The problem of seawater intrusion in a confined coastal aquifer is investigated. The aquifer is overlain by a leaky aquitard and both units extend continuously out under the sea. The problem is formulated in terms of the two governing differential equations, the fluid continuity equation written conveniently in terms of equivalent freshwater head, and the mass continuity equation. Use of linear rectangular finite elements, with direct integration and an iterative solution technique lead to an efficient numerical scheme that is capable of handling long simulation periods. The results, for a 300 m thick aquifer overlain by a 100 m thick aquitard, show that the aquitard has a controlling influence on the salt distribution. A zone of mixing in the aquifer is found to extend for several kilometres in the seaward as well as the landward direction. The time period required by the system to attain a state of dynamic equilibrium after a perturbation is applied may be of the order of centuries. The aquitard is found to cause a downward and seaward displacement of the average salt front.  相似文献   

A synthesis of data from fundamental plane and surface brightness fluctuation surveys     

John P. Blakeslee  John R. Lucey  Brian J. Barris  Michael J. Hudson  John L. Tonry 《Monthly notices of the Royal Astronomical Society》2001,327(3):1004-1020

We perform a series of comparisons between distance-independent photometric and spectroscopic properties used in the surface brightness fluctuation (SBF) and fundamental plane (FP) methods of early-type galaxy distance estimation. The data are taken from two recent surveys: the SBF Survey of Galaxy Distances and the Streaming Motions of Abell Clusters (SMAC) FP survey. We derive a relation between     colour and Mg₂ index using nearly 200 galaxies and discuss implications for Galactic extinction estimates and early-type galaxy stellar populations. We find that the reddenings from Schlegel et al. for galaxies with     appear to be overestimated by     per cent, but we do not find significant evidence for large-scale dipole errors in the extinction map. In comparison with stellar population models having solar elemental abundance ratios, the galaxies in our sample are generally too blue at a given Mg₂; we ascribe this to the well-known enhancement of the α -elements in luminous early-type galaxies. We confirm a tight relation between stellar velocity dispersion σ and the SBF 'fluctuation count' parameter N¯ , which is a luminosity-weighted measure of the total number of stars in a galaxy. The correlation between N¯ and σ is even tighter than that between Mg₂ and σ . Finally, we derive FP photometric parameters for 280 galaxies from the SBF survey data set. Comparisons with external sources allow us to estimate the errors on these parameters and derive the correction necessary to bring them on to the SMAC system. The data are used in a forthcoming paper, which compares the distances derived from the FP and SBF methods.  相似文献   

A new spectroscopic facility at millimetre wavelengths     

A. Baudry  J. Brillet  J. M. Desbats  J. Lacroix  G. Montignac  P. Encrenaz  R. Lucas  G. Beaudin  P. Dierich  A. Germont  P. Landry  G. Rerat 《Journal of Astrophysics and Astronomy》1980,1(2):193-196

A new millimeter-wave facility is in operation at the Bordeaux Observatory for spectroscopic observations of interstellar and stratospheric molecules. A cooled receiver has been installed on a 2·5m radio telescope. The overall system temperature is in the range 400 to 600 K (single side band) in the operating frequency range 75 to 115 GHz. The relatively broad beam of the telescope (∼ 5 arcmin) combined with a sensitive receiver will permit studies of extended molecular cloud complexes.  相似文献   

Impacts of climate and river flooding on the hydro-ecology of a floodplain basin, Peace-Athabasca Delta, Canada since A.D. 1700     

Brent B. Wolfe  Tammy L. Karst-Riddoch  Matthew D. Falcone  Thomas W.D. Edwards 《Quaternary Research》2005,64(2):147-162

Multi-proxy paleolimnological analyses on lake sediment cores from “Spruce Island Lake” (58° 50.82′ N, 111° 28.84′ W), a perched basin in the northern Peace sector of the Peace-Athabasca Delta (PAD), Canada, give insights into the relative roles of flow regulation of the Peace River and climatic variability on the basin hydro-ecology. Results indicate substantial variability in basin hydro-ecology over the past 300 years ranging from seasonal to periodic desiccation in the 1700s to markedly wetter conditions during the early 1800s to early 1900s. The reconstruction is consistent with (1) dry climatic conditions that defined the peak of the Little Ice Age and subsequent amelioration evident in conventional ring-width and isotopic analyses of tree-ring records located hydrologically and climatically upstream of the PAD, and (2) Peace River flood history inferred from sub-annual magnetic susceptibility measurements from another lake sediment record in the Peace sector of the PAD. Although regulation of the Peace River for hydroelectric power generation since 1968 has long been considered a major stressor of the PAD ecosystem leading to reduced frequency of ice-jam and open-water flooding and an extended period of drying, our results show that current hydro-ecological status is not unprecedented as both wetter and drier conditions have persisted for decades in the recent past under natural climatic variability. Furthermore, paleolimnological evidence from Spruce Island Lake indicates that recently observed dryness is part of a longer trend which began some 20-40 years prior to Peace River regulation.  相似文献   

Small scale study of groundwater flow in a fractured carbonate-rock aquifer at the St-Eustache quarry, Québec, Canada     

Jean-Michel Lemieux  René Therrien  Donna Kirkwood 《Hydrogeology Journal》2006,14(4):603-612

A small-scale hydrogeological study was conducted in a fractured carbonate-rock aquifer located in a quarry to relate groundwater flow to the fracture network. The field study in the St-Eustache quarry, which integrates structural surveys, well logging and hydraulic tests, showed that the most important features that affect groundwater flow in the sedimentary aquifer are high hydraulic conductivity horizontal bedding planes. Vertical fractures are abundant in the quarry and throughout the region, but they have a minor effect on groundwater flow. To have a significant impact on the flow regime and lead to vertical groundwater flow, the permeability of all vertical joints need to be enhanced compared to what was generally observed at the site. Such an increase in permeability could potentially occur where dissolution and fracturing is more intense or at stress release locations such as near the surface in the quarry.  相似文献   

新疆北部石炭纪-二叠纪独特的构造-成矿作用：对古亚洲洋构造域南部大地构造演化的制约   总被引：60，自引：53，他引：60  

肖文交  韩春明袁超陈汉林  孙敏林寿发  厉子龙毛启贵  张继恩孙枢 李继亮 《岩石学报》2006,22(5):1062-1076

新疆北部晚古生代独特的构造-成矿作用以发育大量石炭纪-二叠纪构造-成矿事件为特征，其中包括：（1）发育于晚石炭世-二叠世的阿尔泰岛弧及其变质事件、阿尔泰麻粒岩与基性杂岩、西南天山放射虫硅质岩和高压-超高压-低压麻粒岩相变质事件；（2）北疆发育的石炭纪（-二叠世）埃达克岩-高镁安山岩-富Nd玄武质岩组合、阿拉斯加型基性-超基性杂岩和大量的与俯冲相关的钙碱性岩浆活动与斑岩型铜矿床成矿作用；（3）天山晚石炭世晚期蛇绿岩与岛弧火山岩等。结合北疆地区相关的前陆盆地发育不明显、碰撞型花岗岩欠发育与大量发育平行造山带大型走滑构造等现象，可以认为新疆北部在石炭纪-二叠纪挤压-伸展-走滑并存，岩浆活动与成矿作用活跃。这些新进展表明新疆北部在晚石炭世-二叠纪可能仍存在活动陆缘，因此，古亚洲洋构造域南部复杂增生造山作用最后延至晚石炭世晚期-二叠纪。  相似文献