Roadway construction in karst areas: management of stormwater runoff and sinkhole risk assessment   总被引：7，自引：0，他引：7  

Wanfang Zhou  Barry F. Beck 《Environmental Geology》2005,47(8):1138-1149

In karst-rich regions, it is inevitable that roadways cross karst landscapes. Road building across such terranes faces environmental and engineering challenges because of impacts on water quality from stormwater runoff and concerns of sinkhole collapse under or near roadways. When highway runoff drains rapidly into subsurface conduit networks through open sinkholes and/or sinking streams, the impact of the runoff on the karst aquifer can be qualitatively evaluated by mixing cell models. Formulation of a comprehensive stormwater runoff management plan prior to roadway construction can minimize the associated adverse impacts. The commonly used best management practices help manage the stormwater runoff effectively in some sites. Site-specific management plans are preferable for other sites because of concerns of flooding and land stability. Proactive measures should be taken to identify areas of the greatest sinkhole collapse risk along the proposed route and the associated groundwater drainage patterns.  相似文献   

Revisiting a classification scheme for U.S.-Mexico alluvial basin-fill aquifers     

Hibbs BJ  Darling BK 《Ground water》2005,43(5):750-763

Intermontane basins in the Trans-Pecos region of westernmost Texas and northern Chihuahua, Mexico, are target areas for disposal of interstate municipal sludge and have been identified as possible disposal sites for low-level radioactive waste. Understanding ground water movement within and between these basins is needed to assess potential contaminant fate and movement. Four associated basin aquifers are evaluated and classified; the Red Light Draw Aquifer, the Northwest Eagle Flat Aquifer, the Southeast Eagle Flat Aquifer, and the El Cuervo Aquifer. Encompassed on all but one side by mountains and local divides, the Red Light Draw Aquifer has the Rio Grande as an outlet for both surface drainage and ground water discharge. The river juxtaposed against its southern edge, the basin is classified as a topographically open, through-flowing basin. The Northwest Eagle Flat Aquifer is classified as a topographically closed and drained basin because surface drainage is to the interior of the basin and ground water discharge occurs by interbasin ground water flow. Mountains and ground water divides encompass this basin aquifer on all sides; yet, depth to ground water in the interior of the basin is commonly >500 feet. Negligible ground water discharge within the basin indicates that ground water discharges from the basin by vertical flow and underflow to a surrounding basin or basins. The most likely mode of discharge is by vertical, cross-formational flow to underlying Permian rocks that are more porous and permeable and subsequent flow along regional flowpaths beneath local ground water divides. The Southeast Eagle Flat Aquifer is classified as a topographically open and drained basin because surface drainage and ground water discharge are to the adjacent Wildhorse Flat area. Opposite the Eagle Flat and Red Light Draw aquifers is the El Cuervo Aquifer of northern Chihuahua, Mexico. The El Cuervo Aquifer has interior drainage to Laguna El Cuervo, which is a phreatic playa that also serves as a focal point of ground water discharge. Our evidence suggests that El Cuervo Aquifer may lose a smaller portion of its discharge by interbasin ground water flow to Indian Hot Springs, near the Rio Grande. Thus, El Cuervo Aquifer is a topographically closed basin that is either partially drained if a component of its ground water discharge reaches Indian Hot Springs or undrained if all its natural ground water discharge is to Laguna El Cuervo.  相似文献   

Naval power,the law of the sea,and the Indian Ocean as a zone of peace     

Barry Buzan 《Marine Policy》1981,5(3):194-204

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Effect of an acid mine drainage effluent on phytoplankton biomass and primary production at Britannia Beach, Howe Sound, British Columbia     

Levings CD  Varela DE  Mehlenbacher NM  Barry KL  Piercey GE  Guo M  Harrison PJ 《Marine pollution bulletin》2005,50(12):158-1594

We investigated the effect of acid mine drainage (AMD) from an abandoned copper mine at Britannia Beach (Howe Sound, BC, Canada) on primary productivity and chlorophyll a levels in the receiving waters of Howe Sound before, during, and after freshet from the Squamish River. Elevated concentrations of copper (integrated average through the water column >0.050 mg l⁻¹) in nearshore waters indicated that under some conditions a small gyre near the mouth of Britannia Creek may have retained the AMD from Britannia Creek and from a 30-m deep water outfall close to shore. Regression and correlation analyses indicated that copper negatively affected primary productivity during April (pre-freshet) and November (post-freshet). Negative effects of copper on primary productivity were not supported statistically for July (freshet), possibly because of additional effects such as turbidity from the Squamish River. Depth-integrated average and surface chlorophyll a were correlated to copper concentrations in April. During this short study we demonstrated that copper concentrations from the AMD discharge can negatively affect both primary productivity and the standing stock of primary producers in Howe Sound.  相似文献   

The Mesoproterozoic Zig-Zag Dal basalts and associated intrusions of eastern North Greenland: mantle plume–lithosphere interaction     

B.?G.?J.?UptonEmail author  O.?T.?R?m?  L.?M.?Heaman  J.?Blichert-Toft  F.?Kalsbeek  T.?L.?Barry  H.?F.?Jepsen 《Contributions to Mineralogy and Petrology》2005,149(1):40-56

The lavas of the Zig-Zag Dal Formation of eastern North Greenland constitute a Mesoproterozoic tholeiitic flood basalt succession up to 1,350 m thick, extending >10,000 km², and underlain by a sill complex. U–Pb dating on baddeleyite from one of the sills thought to be contemporaneous with the lava extrusion, gives an age of 1,382±2 Ma. The lavas, subdivided from oldest to youngest into Basal, Aphyric and Porphyritic units, are dominantly basaltic (>6 wt.% MgO), with more evolved lavas occurring within the Aphyric unit. The most magnesian lavas occur in the Basal unit and the basaltic lavas exhibit a generalised upward decrease in Mg number (MgO/(MgO + Fe₂O₃^T)) through the succession. All of the lavas are regarded as products of variable degrees of olivine, augite and plagioclase fractionation and to be residual after generation of cumulates in the deep crust. The basaltic lavas display an up-section fall in the ratio of light to heavy rare-earth elements (LREE/HREE) but an up-section rise in Zr/Nb, Sc, Y and HREE. The older lavas (Basal and Aphyric units) are characterised by low _Nd and _Hf in contrast to higher values in the younger (Porphyritic unit) lavas. The Porphyritic Unit basalts are characterised by a notable enrichment in Fe and Ti. The Zig-Zag Dal succession is inferred to reflect an increase in melt fraction in the sub-lithospheric mantle, with melting commencing in garnet–lherzolite facies peridotites and subsequently involving spinel-facies mantle at increasingly shallow depths. Melting is deduced to have occurred beneath an attenuating continental lithosphere in conjunction with ascent of a mantle plume. Lithospheric contamination of primitive melts is inferred to have diminished with time with the Porphyritic unit basalts being products of essentially uncontaminated plume-source magmas. The high iron signature may reflect a relatively iron-rich plume source.  相似文献   

Adaptation in Canadian Agriculture to Climatic Variability and Change   总被引：3，自引：0，他引：3  

Christopher R. Bryant  Barry Smit  Michael Brklacich  Thomas R. Johnston  John Smithers  Quentin Chjotti  Bhawan Singh 《Climatic change》2000,45(1):181-201

The effects of climatic variability and change on Canadian agriculture have become an important research field since the early 1980s. In this paper, we seek to synthesize this research, focusing on agricultural adaptation, a purposeful proactive or reactive response to changes associated with climate, and influenced by many factors. A distinctive feature of methods used in research on adaptation in Canadian agriculture is the focus on the important role of human agency. Many individual farmers perceive they are well adapted to climate, because of their extensive 'technological' tool-kit, giving them confidence in dealing with climatic change. In many regions, little concern is expressed over climatic change, except where there are particular types of climatic vulnerability. Farmers respond to biophysical factors, including climate, as they interact with a complex of human factors. Several of these, notably institutional and political ones, have tended to diminish the farm-level risks stemming from climatic variability and change, but may well increase the long term vulnerability of Canadian agriculture. Notwithstanding the technological and management adaptation measures available to producers, Canadian agriculture remains vulnerable to climatic variability and to climate change.  相似文献   

Observational Evidence of Recent Change in the Northern High-Latitude Environment   总被引：46，自引：1，他引：45  

M. C. Serreze  J. E. Walsh  F. S. Chapin III  T. Osterkamp  M. Dyurgerov  V. Romanovsky  W. C. Oechel  J. Morison  T. Zhang  R. G. Barry 《Climatic change》2000,46(1-2):159-207

Studies from a variety of disciplines documentrecentchange in the northern high-latitude environment.Prompted by predictions of an amplified response oftheArctic to enhanced greenhouse forcing, we present asynthesis of these observations. Pronounced winter andspring warming over northern continents since about 1970ispartly compensated by cooling over the northern NorthAtlantic. Warming is also evident over the centralArcticOcean. There is a downward tendency in sea ice extent,attended by warming and increased areal extent of theArctic Ocean's Atlantic layer. Negative snow coveranomalies have dominated over both continents sincethelate 1980s and terrestrial precipitation has increasedsince 1900. Small Arctic glaciers have exhibitedgenerally negative mass balances. While permafrost haswarmed in Alaska and Russia, it has cooled in easternCanada. There is evidence of increased plant growth,attended by greater shrub abundance and northwardmigration of the tree line. Evidence also suggeststhatthe tundra has changed from a net sink to a net sourceofatmospheric carbon dioxide.Taken together, these results paint a reasonablycoherent picture of change, but their interpretationassignals of enhanced greenhouse warming is open todebate.Many of the environmental records are either short,areof uncertain quality, or provide limited spatialcoverage. The recent high-latitude warming is also nolarger than the interdecadal temperature range duringthis century. Nevertheless, the general patterns ofchange broadly agree with model predictions. Roughlyhalfof the pronounced recent rise in Northern Hemispherewinter temperatures reflects shifts in atmosphericcirculation. However, such changes are notinconsistentwith anthropogenic forcing and include generallypositive phases of the North Atlantic and ArcticOscillations and extratropical responses to theEl-NiñoSouthern Oscillation. An anthropogenic effect is alsosuggested from interpretation of the paleoclimaterecord,which indicates that the 20th century Arctic is thewarmest of the past 400 years.  相似文献   

Beach water table fluctuations due to spring–neap tides: moving boundary effects     

L. Li  D. A. Barry  F. Stagnitti  J. -Y. Parlange  D. -S. Jeng 《Advances in water resources》2000,23(8)

Tidal water table fluctuations in a coastal aquifer are driven by tides on a moving boundary that varies with the beach slope. One-dimensional models based on the Boussinesq equation are often used to analyse tidal signals in coastal aquifers. The moving boundary condition hinders analytical solutions to even the linearised Boussinesq equation. This paper presents a new perturbation approach to the problem that maintains the simplicity of the linearised one-dimensional Boussinesq model. Our method involves transforming the Boussinesq equation to an ADE (advection–diffusion equation) with an oscillating velocity. The perturbation method is applied to the propagation of spring–neap tides (a bichromatic tidal system with the fundamental frequencies ω₁andω₂) in the aquifer. The results demonstrate analytically, for the first time, that the moving boundary induces interactions between the two primary tidal oscillations, generating a slowly damped water table fluctuation of frequency ω₁−ω₂, i.e., the spring–neap tidal water table fluctuation. The analytical predictions are found to be consistent with recently published field observations.  相似文献   

Social Mix and the `Balanced Community' in British housing policy – a tale of two epochs     

Ian Cole  Barry Goodchild 《GeoJournal》2000,51(4):351-360

In Britain, concepts of `social mix' and the `balanced community' provide an example of how policy discourses have adapted to changing conceptions of the role of the state in public provision, forms of social division and inequality, and housing market transformations. The recent development of a policy agenda by the Labour government in Britain devised to promote more socially balanced neighbourhoods is not new, and its lineage may be traced back to the origins of housing and urban policy. However, the manner in which this objective has been framed and the intervention it has provoked have varied considerably over time. One is struck more by the episodic and discontinuous nature of the application of mix and balance in British policy than any sense of a coherent set of strategies pursued through changing times. This paper contrasts the place of social mix and balance in the discourses of the immediate post-war period in Britain with the renewed emphasis on such ideas in the policies of the New Labour government elected in 1997. In the first period, the claims of social mix were infused with the language of national reconstruction and the post-war settlement and the development of universal state provision. More recently, interest in social balance has arisen partly as a response to increased management difficulties and the process of `residualisation' in social housing and partly in response to new concepts of the underclass, social exclusion and social capital. The promotion of social mix and balance in contemporary policy has been shaped by notions of the underclass, social exclusion and the development of social capital in poorer communities. Policy intervention is overtly premised on the assumption that more mixed communities will promote more positive social interaction for residents, despite the lack of evidence for this claim. In practice, much of the discourse has now taken on a stronger sense of discipline and control in order to manage social housing estates. The meaning of social balance remains confused, however, and the achievement of this objective through policy intervention is likely to remain fraught with problems.  相似文献   

Holocene Paleohydrology and Paleoclimate at Treeline, North-Central Russia, Inferred from Oxygen Isotope Records in Lake Sediment Cellulose     

Brent B. Wolfe  Thomas W. D. Edwards  Ramon Aravena  Steven L. Forman  Barry G. Warner  Andrei A. Velichko  Glen M. MacDonald 《Quaternary Research》2000,53(3):319

Lake-water oxygen-isotope histories for three lakes in northern Russia, derived from the cellulose oxygen-isotope stratigraphies of sediment cores, provide the basis for preliminary reconstruction of Holocene paleohydrology in two regions along the boreal treeline. Deconvolution of shifting precipitation δ¹⁸O from secondary evaporative isotopic enrichment is aided by knowledge of the distribution of isotopes in modern precipitation, the isotopic composition of paleo-waters preserved in frozen peat deposits, as well as other supporting paleoclimatic information. These data indicate that during the early Holocene, when the boreal treeline advanced to the current arctic coastline, conditions in the lower Yenisey River region were moist compared to the present, whereas greater aridity prevailed to the east near the lower Lena River. This longitudinal moisture gradient is consistent with the suggestion that oceanic forcing (increased sea-surface temperatures in the Nordic Seas and reduced sea-ice cover) was a major contributor to the development of a more maritime climate in western Eurasia, in addition to increased summer insolation. East of the Taimyr Peninsula, large tracts of the continental shelf exposed by glacial sea-level drawdown may have suppressed maritime climatic influence in what are now coastal areas. In contrast, during the late Holocene the two regions have apparently experienced coherent shifts in effective moisture. The similarity of the records may primarily reflect reduced North Atlantic influence in the Nordic Seas and southward retreat of coastline in eastern Siberia, coupled with declining summer insolation.  相似文献