Evaluation of heterogeneity and field-scale groundwater flow regime in a leaky till aquitard   总被引：2，自引：1，他引：2  

Richard E. Gerber  Joseph I. Boyce  Ken W. Howard 《Hydrogeology Journal》2001,9(1):60-78

Recent work in southern Ontario, Canada, demonstrates anomalously high vertical groundwater flow velocities (>1 m/year) through a thick (as much as 60 m), sandy silt till aquitard (Northern till), previously assumed to be of very low permeability (hydraulic conductivity <10^–10 m/s). Rapid recharge is attributed to the presence of fractures and sedimentary heterogeneities within the till, but the field-scale flow regime is poorly understood. This study identifies the nature of physical groundwater pathways through the till and provides estimates of the associated groundwater fluxes. The aquitard groundwater flow system is characterized by integrating details of the outcrop and subsurface sedimentary characteristics of the till with field-based hydrogeologic investigation and numerical modeling. Outcrop and subsurface data identify a composite internal aquitard stratigraphy consisting of tabular till beds (till elements) separated by laterally continuous sheet-like sands and gravels (interbeds) and boulder pavements. Individual till elements contain sedimentary heterogeneities, including discontinuous sand and gravel lenses, vertical sand dikes, and zones of horizontal and vertical fractures. Hydrogeologic field investigations indicate a three-layer aquitard flow system, consisting of upper and lower zones of more hydraulically active and heterogeneous till separated by a middle unit of relatively lower hydraulic conductivity. Groundwater pathways and fluxes in the till were evaluated using a two-dimensional aquitard/aquifer flow model which indicates a step-wise flow mechanism whereby groundwater moves alternately downward along vertical pathways (fractures, sedimentary dikes) and laterally along horizontal sand interbeds within the till. This model is consistent with observed hydraulic-head and isotope profiles, and the presence of tritiated pore waters at various depths throughout the till. Simulations suggest that a bulk aquitard vertical hydraulic conductivity on the order of 1×10^–9 m/s is required to reproduce observed hydraulic-head and tritium profiles. Electronic Publication  相似文献   

Giant mineral deposits and underlying Earth processes     

Adrian Joseph Boyce  Iain McDonald 《Mineralium Deposita》2005,40(5):449-450

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A multibeam H i survey of the Virgo cluster – two isolated H i clouds?     

J. Davies  R. Minchin  S. Sabatini  W. van Driel  M. Baes  P. Boyce  W. J. G. de Blok  M. Disney  Rh. Evans  V. Kilborn  R. Lang  S. Linder  S. Roberts  R. Smith 《Monthly notices of the Royal Astronomical Society》2004,349(3):922-932

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Comment on a Formula for the Gravitational Harmonic Coefficients of a Triaxial Ellipsoid   总被引：1，自引：0，他引：1  

William Boyce 《Celestial Mechanics and Dynamical Astronomy》1997,67(2):107-110

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Remote sensing photometric studies of Mars in 1971     

Peter Boyce 《Icarus》1973,18(1):134-141

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Evidence for microbial activity in British and Irish Ordovician pillow lavas     

John Parnell  Malcolm Hole  Adrian J. Boyce 《Geological Journal》2015,50(4):497-508

Pyrite is consistently found in modern seafloor vesicular basalts and has a sulphur isotopic composition consistent with microbial activity. We present S isotope data from pyrite in Ordovician pillow lavas at localities across the British Isles, which yield a range of δ³⁴S compositions consistent with two components of sulphur: groundmass pyrite (~0 ± 4‰) and ³²S‐enriched pyrite in the vesicles (−8‰ to −27‰). The latter are recorded from vesicular lavas in four different terranes, representing different settings at the margins of the Iapetus Ocean. Whereas a component of magmatic sulphate is recognized in the groundmass values, the isotopically light data in the vesicles are consistent with microbial reduction of seawater sulphate in sub‐seafloor lavas. This is consistent with modern examples and indicates considerable longevity for this sub‐seafloor microbial habitat. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Summer thermal structure of lake Ontario off Toronto: Cooling the big city     

F.M. Boyce  D.G. Robertson  G.N. Ivey 《大气与海洋》2013,51(4):397-417

Abstract

It has been proposed that large savings in electrical energy are possible if cool, deep water from Lake Ontario is used, as an alternative to electrically operated chillers, to provide the cooling requirements of large buildings in down‐town Toronto. In order to estimate the capital expenditure involved, it is necessary to determine how deep (and how far offshore) the cold water intake must be placed to obtain a reliable supply of cool water throughout the air‐conditioning season. Temperature profile data, collected during ship surveys over the past twenty years in Lake Ontario off Toronto, plus time‐series data from a 21‐level thermistor array installed on the 100‐m contour near the site of the proposed intake during the summer of 1980, have been used to answer this specific question. The two sets are examined to determine the relative importance of thermal variability for inter‐annual, seasonal, and shorter time‐scales. Intake design turns out to be an important consideration for the air‐conditioning scheme. Unless azimuthal swirling velocities are restrained at the intake, drawdown of warmer thermocline water into the intake may occur.  相似文献   

The large-scale distribution of neutral hydrogen in the Fornax region     

Meryl Waugh  M. J. Drinkwater  R. L. Webster  L. Staveley-Smith  V. A. Kilborn  D. G. Barnes  R. Bhathal  W. J. G. de Blok  P. J. Boyce  M. J. Disney  R. D. Ekers  K. C. Freeman  B. K. Gibson  P. A. Henning  H. Jerjen  P. M. Knezek  B. Koribalski  M. Marquarding  R. F. Minchin  R. M. Price  M. E. Putman  †  S. D. Ryder  E. M. Sadler  F. Stootman  M. A. Zwaan 《Monthly notices of the Royal Astronomical Society》2002,337(2):641-656

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Surface brightness bias in galaxy catalogues; distance effects     

S. Phillipps  J. I. Davies  P. J. Boyce  Rh. Evans 《Astrophysics and Space Science》1993,207(1):91-104

We have investigated the apparent variation of the surface brightness distribution of disc galaxies with distance within three different samples 1) a diameter limited sample of ESO catalogue galaxies in the direction of the cluster A3574 in Centaurus, 2) all ESO catalogue disc galaxies with redshifts, and 3) a sample of fainter galaxies from our surveys of the Fornax Cluster area. In each case we find, as predicted for a sample dominated by surface brightness selection effects, that the distribution narrows with distance. Both high and low surface brightness galaxies are underrepresented in galaxy catalogues. Not because they are rare, but because the volume over which they are sampled is considerably smaller than that of their normal surface brightness counterparts. The question of how many galaxies there are in the Universe remains un-answered. In addition, since selection is byapparent surface brightness, the most distant sample (where cosmological dimming becomes important) contains galaxies of higher intrinsic surface brightness than do the nearby samples, again confirming a previous theoretical prediction. The galaxies we observe in the distant Universe are very different to those we observe close by because of observational selection.  相似文献   

Constraints on the development of orogenic style gold mineralisation at Mineral de Talca,Coastal Range,central Chile: evidence from a combined structural,mineralogical, S and Pb isotope and geochronological study     

Emily A. Firth  David A. Holwell  Nicholas H. S. Oliver  James K. Mortensen  Matthew P. Rovardi  Adrian J. Boyce 《Mineralium Deposita》2015,50(6):675-696

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