Effect of rapidly changing river stage on uranium flux through the hyporheic zone   总被引：2，自引：1，他引：1  

Fritz BG  Arntzen EV 《Ground water》2007,45(6):753-760

Measurement of ground water/surface water interaction within the hyporheic zone is increasingly recognized as an important aspect of subsurface contaminant fate and transport. Understanding the interaction between ground water and surface water is critical in developing a complete conceptual model of contaminant transport through the hyporheic zone. At the Hanford Site near Richland, Washington, ground water contaminated with uranium discharges to the Columbia River through the hyporheic zone. Ground water flux varies according to changes in hydraulic gradient caused by fluctuating river stage, which changes in response to operation of dams on the Columbia River. Piezometers and continuous water quality monitoring probes were installed in the hyporheic zone to provide long-term, high-frequency measurement of hydraulic gradient and estimated uranium concentrations. Subsequently, the flux of water and uranium was calculated for each half-hour time period over a 15-month study period. In addition, measurement of water levels in the near-shore unconfined aquifer enhanced the understanding of the relationship between river stage, aquifer elevation, and uranium flux. Changing river stage resulted in fluctuating hydraulic gradient within the hyporheic zone. Further, influx of river water caused lower uranium concentrations as a result of dilution. The methods employed in this study provide a better understanding of the interaction between surface and ground water in a situation with a dynamically varying vertical hydraulic gradient and illustrate how the combination of relatively standard methods can be used to derive an accurate estimation of water and contaminant flux through the hyporheic zone.  相似文献   

Facilitating adaptation to global climate change: perspectives from experts and decision makers serving the Florida Keys   总被引：2，自引：1，他引：1  

Evan Flugman  Pallab Mozumder  Timothy Randhir 《Climatic change》2012,112(3-4):1015-1035

Slivers of land amidst the world’s third largest barrier reef, the Florida Keys provide unique insights on the emerging challenges associated with adaptation to global climate change. While political will and public awareness are gradually shifting on the imposing risks, analysis of survey responses from experts and decision makers serving the Florida Keys (federal, state and local personnel) reveals insufficient resources, limited direction and leadership, and lack of institutional frameworks to facilitate the adaptation process. Against this backdrop, we investigate experts and decision makers’ interest in an array of adaptation measures including their willingness to support a proposed ‘Community Adaptation Fund’ (CAF) to mobilize resources and lay the foundation for adaptation initiatives in the Florida Keys. We also explore potential funding sources for establishing the proposed CAF, and test the feasibility of a diverse set of financing mechanisms. We discuss implications of our findings in the context of enhancing adaptive capacity in the Florida Keys and beyond.  相似文献   

Lagrangian coherent structures in the planar elliptic restricted three-body problem     

Evan S. Gawlik  Jerrold E. Marsden  Philip C. Du Toit  Stefano Campagnola 《Celestial Mechanics and Dynamical Astronomy》2009,103(3):227-249

This study investigates Lagrangian coherent structures (LCS) in the planar elliptic restricted three-body problem (ER3BP), a generalization of the circular restricted three-body problem (CR3BP) that asks for the motion of a test particle in the presence of two elliptically orbiting point masses. Previous studies demonstrate that an understanding of transport phenomena in the CR3BP, an autonomous dynamical system (when viewed in a rotating frame), can be obtained through analysis of the stable and unstable manifolds of certain periodic solutions to the CR3BP equations of motion. These invariant manifolds form cylindrical tubes within surfaces of constant energy that act as separatrices between orbits with qualitatively different behaviors. The computation of LCS, a technique typically applied to fluid flows to identify transport barriers in the domains of time-dependent velocity fields, provides a convenient means of determining the time-dependent analogues of these invariant manifolds for the ER3BP, whose equations of motion contain an explicit dependency on the independent variable. As a direct application, this study uncovers the contribution of the planet Mercury to the Interplanetary Transport Network, a network of tubes through the solar system that can be exploited for the construction of low-fuel spacecraft mission trajectories. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Self-regulation of active galactic nuclei in galaxy clusters     

Marcus Brüggen  Evan Scannapieco 《Monthly notices of the Royal Astronomical Society》2009,398(2):548-560

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Priming the Pump for In Situ Treatment     

Evan K. Nyer 《Ground Water Monitoring & Remediation》1986,6(4):4-5

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May the Force Be with You     

Evan K. Nyer  Gary Boettcher  Pete Jalajas 《Ground Water Monitoring & Remediation》1997,17(3):70-75

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Biochemical Effects on Contaminant Fate and Transport     

Evan K. Nyer  Victoria Kramer  Nicholas Valkenburg 《Ground Water Monitoring & Remediation》1991,11(2):80-82

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All Sites Cannot Be "Clean"     

Evan K. Nyer  Douglas Hatler 《Ground Water Monitoring & Remediation》1992,12(3):91-93

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Treatment System Operation and Maintenance: Critical Factors in an Economic Analysis     

Evan K. Nyer  Gregory Rorech 《Ground Water Monitoring & Remediation》1992,12(4):97-99

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The Political Design     

Evan K. Nyer 《Ground Water Monitoring & Remediation》1994,14(1):74-78

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