Excess air during aquifer storage and recovery in an arid basin (Las Vegas Valley, USA)     

D. Kip Solomon  Erin Cole  Joseph F. Leising 《Hydrogeology Journal》2011,19(1):187-194

The Las Vegas Valley Water District in Nevada, USA, has operated an artificial recharge (AR) program since 1989. In summer 2001, observations of gas exsolving from tap water prompted a study that revealed total dissolved gas (TDG) pressures approaching 2?atm with a gas composition that it is predominantly air. Measurements of TDG pressure at well heads and in the distribution system indicated two potential mechanisms for elevated TDG pressures: (1) air entrainment during AR operations, and (2) temperature changes between the winter recharge season and the summer withdrawal season. Air entrainment during pumping was investigated by intentionally allowing the forebay (upstream reservoir) of a large pumping station to drawdown to the point of vortex formation. This resulted in up to a 0.7?atm increase in TDG pressure. In general, the solubility of gases in water decreases as the temperature increases. In the Las Vegas Valley, water that acquired a modest amount of dissolved gas during winter artificial recharge operations experienced an increase in dissolved gas pressure (0.04?atm/°C) as the water warmed in the subsurface. A combination of air entrainment during AR operations and its amplification by temperature increase after recharge can account for most of the observed amounts of excess gas at this site.  相似文献   

Testing resilience thinking in a poverty context: Experience from the Niger River basin     

Christophe Béné  Louisa Evans  David Mills  Solomon Ovie  Aminu Raji  Ahmadu Tafida  Amaga Kodio  Famory Sinaba  Pierre Morand  Jacques Lemoalle  Neil Andrew 《Global Environmental Change》2011,21(4):1173-1184

Resilience thinking is an important addition to the range of frameworks and approaches that can be used to understand and manage complex social–ecological systems like small-scale fisheries. However, it is yet to lead to better environmental or development outcomes for fisheries stakeholders in terms of food security, improved livelihoods and ecological sustainability. This paper takes an empirical approach by focusing on the fundamentals of resilience thinking to evaluate its usefulness in developing relevant management interventions in small-scale fisheries in the Niger River Basin in West Africa. The paper presents the outputs of a participatory assessment exercise where both fishery communities and local experts were involved at two different scales. The resilience frame used was designed to facilitate the identification of socially defined thresholds that help delineate the desirability of the current system configuration and provides a diagnosis framework that tailors management solutions to problems in local context. The analysis highlights some key contributions from resilience thinking to the challenge of diagnosis in small-scale fisheries management in developing countries, as well as important contributions that emerge from taking a pragmatic and critical approach to its application.  相似文献   

Lateglacial vegetation and palaeoenvironment in W Norway,with new pollen data from the Sunnmøre region     

LINN CECILIE KRÜGER  AAGE PAUS  JOHN INGE SVENDSEN  ANNE E. BJUNE 《Boreas: An International Journal of Quaternary Research》2011,40(4):616-635

Krüger, L. C., Paus, A., Svendsen, J. I. & Bjune, A. E. 2011: Lateglacial vegetation and palaeoenvironment in W Norway, with new pollen data from the Sunnmøre region. Boreas, 10.1111/j.1502‐3885.2011.00213.x. ISSN 0300‐9483. Two sediment sequences from Sunnmøre, northern W Norway, were pollen‐analytically studied to reconstruct the Lateglacial vegetation history and climate. The coastal Dimnamyra was deglaciated around 15.3 ka BP, whereas Løkjingsmyra, further inland, became ice‐free around 14 ka BP. The pioneer vegetation dominated by snow‐bed communities was gradually replaced by grassland and sparse heath vegetation. A pronounced peak in Poaceae around 12.9 ka BP may reflect warmer and/or drier conditions. The Younger Dryas (YD) cooling phase shows increasing snow‐bed vegetation and the local establishment of Artemisia norvegica. A subsequent vegetation closure from grassland to heath signals the Holocene warming. Birch forests were established 500–600 years after the YD–Holocene transition. This development follows the pattern of the Sunnmøre region, which is clearly different from the Empetrum dominance in the Lateglacial interstadial further south in W Norway. The Lateglacial oscillations GI‐1d (Older Dryas) and GI‐1b (Gerzensee) are hardly traceable in the north, in contrast to southern W Norway. The southern vegetation was probably closer to an ecotone and more susceptible to climate changes.  相似文献   

Seismic fragility of reinforced concrete girder bridges using Bayesian belief network          下载免费PDF全文

Paolo Franchin  Alessio Lupoi  Fabrizio Noto  Solomon Tesfamariam 《地震工程与结构动力学》2016,45(1):29-44

Infrastructure owners and operators, or governmental agencies, need rapid screening tools to prioritize detailed risk assessment and retrofit resources allocation. This paper provides one such tool, for use by highway administrations, based on Bayesian belief network (BBN) and aimed at replacing so‐called generic or typological seismic fragility functions for reinforced concrete girder bridges. Resources for detailed assessments should be allocated to bridges with highest consequence of damage, for which site hazard, bridge fragility, and traffic data are needed. The proposed BBN based model is used to quantify seismic fragility of bridges based on data that can be obtained by visual inspection and engineering drawings. Results show that the predicted fragilities are of sufficient accuracy for establishing relative ranking and prioritizing. While the actual data and seismic hazard employed to train the network (establishing conditional probability tables) refer to the Italian bridge stock, the network structure and engineering judgment can easily be adopted for bridges in different geographical locations. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Dynamics of the Mackenzie River plume on the inner Beaufort shelf during an open water period in summer     

Ryan P. Mulligan  Will Perrie  Steve Solomon 《Estuarine, Coastal and Shelf Science》2010

The oceanographic conditions of the Mackenzie River plume in the Arctic Ocean were examined during a 12-day period in August 2007. Field observations in the river channel and the delta region (2–6 m depth), ship-based observations on the shelf and satellite observations of sea surface temperatures indicate that movements of plume density fronts cause changes in water temperatures of over 10  C over a few days. We used a 1D model to compare the strength of stratification versus surface wind stress, and a 3D numerical model to simulate the plume motions under forcing from the river flows, local wind and water level variations from tides and wind-driven surge. The results indicate that the coastal region is stratified with a ∼2 m thick surface plume even in water depths of 3–4 m, resulting in strong vertical variation of horizontal currents. Moderate easterly winds of 5–10 m/s are sufficient to induce offshore transport of the surface plume and onshore transport of the deeper shelf water, leading to large fluctuations in temperature and salinity in the coastal region. This study examined a period of offshore transport and mean water level set-down, and indicates the rapid response of the plume to wind over the shallow delta.  相似文献   

The glacial succession on the North Norfolk Coast     

J.D. Solomon 《Proceedings of the Geologists' Association. Geologists' Association》1932,43(3):241-IN5

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Pacific subtropical cell variability in coupled climate model simulations of the late 19th–20th century     

Amy Solomon  Dongxiao Zhang 《Ocean Modelling》2006,15(3-4):236

Observational studies of the Pacific basin since the 1950s have demonstrated that a decrease (increase) in tropical Pacific sea surface temperatures (SSTs) is significantly correlated with a spin-up (slow-down) of the Pacific Subtropical Cells (STCs). STCs are shallow wind-driven overturning circulations that provide a pathway by which extratropical atmospheric variability can impact the equatorial Pacific thermocline and, through upwelling in the eastern equatorial Pacific, tropical Pacific SSTs. Recent studies have shown that this observed relationship between SSTs and STCs is absent in coupled climate model simulations of the late 19th–20th centuries. In this paper we investigate what causes this relationship to breakdown and to what extent this limits the models’ ability to simulate observed climate change in the equatorial Pacific since the late 19th century. To provide insight into these questions we first show that the NCAR Community Climate System Model’s simulation of observed climate change since the 1970s has a robust signal in the equatorial Pacific that bears a close resemblance to observations. Strikingly, absent is a robust signal in the equatorial thermocline. Our results suggest that the coupled model may be reproducing the observed local ocean response to changes in forcing but inadequately reproducing the remote STC-forcing of the tropical Pacific due to the underestimate of extratropical winds that force these ocean circulations. These conclusions are found to be valid in five different coupled climate model simulations of the late 19th–20th centuries (CCSM3, GISS EH, GFDL CM2.1, CSIRO-Mk3, and HadCM3).  相似文献   

Arctic Coastal Dynamics (ACD): an introduction     

Volker Rachold  Feliks E. Are  David E. Atkinson  Georgy Cherkashov  Steven M. Solomon 《Geo-Marine Letters》2005,25(2-3):63-68

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Mercury: Internal structure and thermal evolution     

Robert W. Siegfried  Sean C. Solomon 《Icarus》1974,23(2):192-205

Astronomical observations and cosmochemical calculations suggest that the planet Mercury may be composed of materials which condensed at relatively high temperatures in the primitive solar nebula and may have a basaltic crust similar to parts of the moon. These findings, plus the long standing inference that Mercury is much richer in metallic iron than the other terrestrial planets, provide important constraints which we apply to models of the thermal evolution and density structure of the planet. The thermal history calculations include explicitly the differing thermal properties of iron and silicates and account for core segregation, melting and differentiation of heat sources, and simulated convection during melting. If the U and Th abundances of Mercury are taken from the cosmochemical model of Lewis, then the planet would have fully differentiated a metal core from the silicate mantle for all likely initial temperature distributions and heat transfer properties. Density distributions for the planet are calculated from the mean density and estimates of the present-day temperature. For the fully differentiated model, the moment of inertia C/MR² is 0.325 (J₂=0.302×10^?6). For models with lower heat source abundances, the planet may not yet have differentiated. The density profiles for such models give C/MR²=0.394 (J₂=0.487×10^?6). These results should be useful for preliminary interpretation of the Mariner 10 measurements of Mercury's gravitational field.  相似文献   

Lajishan accretionary complex: Implications for Paleozoic accretionary and collisional events in the South Qilian belt     

YAN Zhen  FU Changlei  Jonathan AITCHISON  Solomon BUCHMON  NIU Manlan 《《地质学报》英文版》2018,92(Z2):41-41

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