Geo-feasibility of in situ sediment capping in a Great Lakes urban estuary: a sediment budget assessment     

Anthony M. Foyle  Kevin P. Norton 《Environmental Geology》2007,53(2):271-282

Presque Isle Bay is one of 40 remaining environmental areas of concern (AoCs) on the North American Great Lakes that have one or more water, habitat, or sediment quality impairments as defined by the International Joint Commission. In situ natural capping using sediment from to-be-remediated watersheds and other potential sources is being considered as the most feasible means of remediating an existing contaminated sediment problem at this site. A multi-decade (∼40 year) sediment budget shows that, when localized anthropogenic effects (dredging, reclamation) are discounted, the bay net-accumulated sediment over time. Sediment was supplied from three major sources: bank erosion and bluff retreat (41%), streams (25%), and the Lake Erie littoral system (20%). The non-stream sources supply environmentally clean materials from ancient beach and glacio-lacustrine deposits along the shoreline, and from the modern littoral system. Organic and metallic contaminants supplied primarily by streams and run-off remain a remediation challenge for the AoC. Geologically, natural capping of contaminants over the next several decades is a viable solution for most of the bay. The mechanism may not work effectively in all areas because approximately 25% of the bay floor is moderately net-erosional while several localized areas accumulate sediments very slowly at decadal timescales.  相似文献   

Multiple-method estimation of recharge rates at diverse locations in the North Carolina Coastal Plain, USA   总被引：1，自引：0，他引：1  

A. L. Coes  T. B. Spruill  M. J. Thomasson 《Hydrogeology Journal》2007,15(4):773-788

Recharge rates determined at diverse study sites in a shallow, unconfined aquifer differed from one another depending on the analytical method used and on each method’s applicability and limitations. Total recharge was quantified with saturated-zone methods using water-table fluctuations at seven sites in North Carolina, USA and using groundwater-age dating at three of the seven sites; at two of the sites, potential recharge was quantified with an unsaturated-zone method using Darcy’s law; and at five of the sites, net recharge was quantified with a stream hydrograph-separation method using streamflow-recession curves. Historical mean net recharge was 25 to 69% of the historical total recharge rates. The large disparity is attributed to groundwater losses between recharge and discharge areas, primarily by evapotranspiration and seepage to underlying aquifers. The spatial distribution of historical mean annual total recharge did not vary between landscape units, as suggested in a previous study. Similarly, total recharge did not correlate significantly with mean annual rainfall, mean annual water table depth, or the surficial soil properties of percent clay and bulk density. Total recharge did correlate significantly with the surficial soil properties of percent sand and percent silt.

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Résumé Les taux de recharge déterminés sur divers sites d’études dans un aquifère phréatique libre, varient les uns par rapport aux autres selon la méthode analytique utilisée et les limites et l’applicabilité de chaque méthode. La recharge totale a été quantifiée avec des méthodes en zone saturée utilisant les fluctuations des nappes sur sept sites de la Caroline du Nord, USA, et en utilisant les datations des eaux souterraines sur trois des sept sites ; sur deux des sites, la recharge potentielle a été quantifiée avec une méthode en zone non-saturée utilisant la loi de Darcy, et sur deux sites, la recharge nette a été quantifiée suivant une méthode de séparation des hydrographes de cours d’eau utilisant les courbes de récession du débit. La moyenne historique de la recharge nette est comprise entre 25 et 69% des taux historiques de recharge totale. L’importante disparité est attribuée aux pertes en eaux souterraines entre les zones de recharge et les zones d’exutoire, d’abord par évapotranspiration et ensuite par infiltration vers les aquifères sous-jacents. La distribution spatiale de la recharge historique moyenne annuelle et totale ne varie pas selon les unités paysagères, comme cela était suggéré dans une étude antérieure. De même, la recharge totale n’est pas corrélée significativement avec la moyenne annuelle des précipitations, la moyenne annuelle de la profondeur de la nappe, ou les propriétés de surface des sols que sont le pourcentage d’argile ou la densité apparente. La recharge totale est corrélée significativement avec les propriétés de surface du sol et les teneurs en sable et en silt.

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Resumen Las tasas de recarga determinadas en diversos sitios de estudio en un acuífero somero no confinado difieren entre sí dependiendo del método analítico usado y de las limitaciones y aplicabilidad de cada método. Se cuantificó la recarga total con métodos de zona saturada usando fluctuaciones del nivel freático en siete sitios en Carolina del Norte, Estados Unidos, y usando datación de edades de agua subterránea en tres de los siete sitios; en dos de los sitios se cuantificó la recarga potencial con un método de zona no saturada usando la Ley de Darcy y en cinco de los sitios se cuantificó la recarga neta con el método de separación hidrográfica usando curvas de recesión de flujo en arroyos. La recarga neta media histórica varió entre 25 y 69% de las tasas de recarga total histórica. La diferencia tan grande se atribuye a pérdidas de agua subterránea entre áreas de descarga y recarga, principalmente por evapotranspiración y escurrimiento hacia acuíferos subyacentes. La distribución espacial de la recarga total anual media histórica no varió entre las unidades de paisaje, como ya se había sugerido en un estudio previo. De modo similar, la recarga total no guarda correlación significativa con la lluvia media anual, la profundidad media anual del nivel freático, o las propiedades superficiales del suelo, particularmente porcentaje de arcilla y densidad volumétrica. La recarga total si tuvo una correlación significativa con las propiedades superficiales del suelo tal como porcentaje de arena y porcentaje de limo.

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Dripping into unsaturated rock underground excavations—literature review and geologic and hydrogeologic setting description     

Amvrossios C. Bagtzoglou  Daniele Cesano 《Environmental Geology》2007,51(8):1285-1294

A literature review of dripping in underground constructions in deep, unsaturated geologic media was performed as part of a phased study. The objective is to develop and test a formulation that can be used for studying unsaturated flow through rough multi-segmented fractures, with emphasis on predicting dripping initiation time. Geologic and hydrogeologic setting for the Yucca Mountain (YM) and its exploratory studies facility, which is the site where the model will be tested, are described.  相似文献   

River plume patterns and dynamics within the Southern California Bight     

J.A. Warrick  P.M. DiGiacomo  S.B. Weisberg  N.P. Nezlin  M. Mengel  B.H. Jones  J.C. Ohlmann  L. Washburn  E.J. Terrill  K.L. Farnsworth 《Continental Shelf Research》2007

Stormwater river plumes are important vectors of marine contaminants and pathogens in the Southern California Bight. Here we report the results of a multi-institution investigation of the river plumes across eight major river systems of southern California. We use in situ water samples from multi-day cruises in combination with MODIS satellite remote sensing, buoy meteorological observations, drifters, and HF radar current measurements to evaluate the dispersal patterns and dynamics of the freshwater plumes. River discharge was exceptionally episodic, and the majority of storm discharge occurred in a few hours. The combined plume observing techniques revealed that plumes commonly detach from the coast and turn to the left, which is the opposite direction of Coriolis influence. Although initial offshore velocity of the buoyant plumes was ∼50 cm/s and was influenced by river discharge inertia (i.e., the direct momentum of the river flux) and buoyancy, subsequent advection of the plumes was largely observed in an alongshore direction and dominated by local winds. Due to the multiple day upwelling wind conditions that commonly follow discharge events, plumes were observed to flow from their respective river mouths to down-coast waters at rates of 20–40 km/d. Lastly, we note that suspended-sediment concentration and beam-attenuation were poorly correlated with plume salinity across and within the sampled plumes (mean r²=0.12 and 0.25, respectively), while colored dissolved organic matter (CDOM) fluorescence was well correlated (mean r²=0.56), suggesting that CDOM may serve as a good tracer of the discharged freshwater in subsequent remote sensing and monitoring efforts of plumes.  相似文献   

Seasonality of diel cycles of dissolved trace-metal concentrations in a Rocky Mountain stream   总被引：4，自引：0，他引：4  

David A. Nimick  Thomas E. Cleasby  R. Blaine McCleskey 《Environmental Geology》2005,47(5):603-614

Substantial diel (24-h) cycles in dissolved (0.1-m filtration) metal concentrations were observed during summer low flow, winter low flow, and snowmelt runoff in Prickly Pear Creek, Montana. During seven diel sampling episodes lasting 34–61.5 h, dissolved Mn and Zn concentrations increased from afternoon minimum values to maximum values shortly after sunrise. Dissolved As concentrations exhibited the inverse timing. The magnitude of diel concentration increases varied in the range 17–152% for Mn and 70–500% for Zn. Diel increases of As concentrations (17–55%) were less variable. The timing of minimum and maximum values of diel streamflow cycles was inconsistent among sampling episodes and had little relation to the timing of metal concentration cycles, suggesting that geochemical rather than hydrological processes are the primary control of diel metal cycles. Diel cycles of dissolved metal concentrations should be assumed to occur at any time of year in any stream with dissolved metals and neutral to alkaline pH.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.  相似文献   

Groundwater as an environmental constraint of longwall coal mining   总被引：6，自引：0，他引：6  

C.J. Booth 《Environmental Geology》2006,49(6):796-803

Groundwater impacts are a common reason for opposition to longwall mining. Most impacts are due to subsidence-related fracturing. Although upper aquifers are protected from drainage to the mine by a confining zone, water levels decline due to fracture dilation, and drawdown expands outward a few hundred meters. Recovery of water levels is common.  相似文献   

Is there an Insect Signal for the "Little Ice Age"?     

Paul C. Buckland  Pat E. Wagner 《Climatic change》2001,48(1):137-149

The downturn in temperature in the late medieval period is likely to have had significant impact upon insect distribution. Despite the amount of study fossil insect faunas have been afforded, there is presently little convincing evidence of climatic, rather than human impact upon faunas during the "Little Ice Age". This probably reflects as much the paucity of suitable sites, as the overarching scale of habitat destruction by Man.  相似文献   

A Petroleum System for the Salina Basin in Kansas Based on Organic Geochemistry and Geologic Analog     

K. David Newell  Joseph R. Hatch 《Natural Resources Research》2000,9(3):169-200

The Salina Basin historically has been an exploration desert—a home of dryholes. Although this basin, which underlies much of north-central Kansas, may never be a prolific source of hydrocarbons, recent research into the maturation and geochemistry of organic matter and oils in Kansas can provide guidelines for a new exploration strategy. The Salina Basin is similar to the oil-productive Forest City Basin in northeastern Kansas in many ways. Both basins originated as a single large basin (i.e., the North Kansas Basin) prior to the rise of the Nemaha Uplift in Late Mississippian-Early Pennsylvanian time. Their Paleozoic stratigraphy thus is similar and the axes of both basins are presently at approximately the same depth. Thermal maturation modeling and available organic-matter maturation data indicate that the lower Paleozoic rocks in the axes of both basins are in the early stages of oil generation. In the Forest City Basin the Ordovician Simpson Group is the deepest known hydrocarbon source-rock—oil-reservoir interval, and by analogy, exploration tests in the Salina Basin, at a minimum, should penetrate through this stratigraphic interval. Ordovician Simpson Group shales in the Forest City Basin are the source rocks for a geochemically distinct oil, which also occurs in Ordovician reservoirs in the extreme southern end of the Salina Basin. To increase the odds of success in an exploration program in the Salina Basin, wildcat wells should be drilled where thermal maturation is greatest. The broad NW–SE-trending basin axis is the most logical area. Exploration tests along this axis in the northern end of the basin may have an extra advantage as organic matter in the Simpson Group may be more thermally mature because of greater burial depth during the Cretaceous. Along the eastern margin of the nearby Central Kansas Uplift and Pratt Anticline, several Paleozoic geologic structures, some of which contain major oil fields, are attributable to tectonic reactivation along the western margin of the Precambrian Central North American Rift System (CNARS). Prospective structural trends in the Paleozoic section of the Salina Basin are anticipated to be associated with this underlying tectonic boundary. The western margin of the CNARS trends NNE–SSW where it passes under the axis of the Salina Basin in northeastern Lincoln and southeastern Mitchell counties. This area is sparsely drilled, with less than two tests per township. If an exploration program can define lower Paleozoic structural closures in this region, these structures may represent the best chance for future petroleum discoveries.  相似文献   

The effects of Holocene barrier-island evolution on water-table elevations, Hatteras Island, North Carolina, USA     

William P. Anderson Jr.  David G. Evans  Stephen W. Snyder 《Hydrogeology Journal》2000,8(4):390-404

 On Hatteras Island, North Carolina, USA, complex stratigraphy results from surficial sediments being superimposed on an inherited Pleistocene platform. Numerical simulations used to simulate water-table profiles on the island illustrate the influence that the complex stratigraphy has on water-table elevations. Field data consist of water-table profiles collected from a cross-island transect of wells. These profiles show unusually high water-table elevations in the south-central portion of Hatteras Island. Geophysical data are used to constrain the subsurface stratigraphy. Simple analytical solutions to the groundwater flow equation using laterally varying recharge rates cannot match mean water-table profiles. More complex numerical simulations, which do match the profiles, indicate that the elevated water levels result from a low-permeability unit that extends several kilometers along the longitudinal axis of the island. Island geomorphology and ground-penetrating radar (GPR) data suggest that this unit is a former interdunal wetland that has been buried by a series of parabolic dunes. Received, September 1999 / Revised, March 2000 / Accepted, March 2000  相似文献   

Reply to comment by Javier Rodríguez on “Sulfate transport in a Coastal Plain confining unit, New Jersey, USA” (Pucci 1999)     

Amleto A. Pucci Jr. 《Hydrogeology Journal》2000,8(4):451-454

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