Nordic home ports for ships     

Gunnar Allexandersson 《GeoJournal》1981,2(2):97-106

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Groundwater ‐ the disregarded component in lake water and nutrient budgets. Part 1: effects of groundwater on hydrology          下载免费PDF全文

Donald O. Rosenberry  Jörg Lewandowski  Karin Meinikmann  Gunnar Nützmann 《水文研究》2015,29(13):2895-2921

Lake eutrophication is a large and growing problem in many parts of the world, commonly due to anthropogenic sources of nutrients. Improved quantification of nutrient inputs is required to address this problem, including better determination of exchanges between groundwater and lakes. This first of a two‐part review provides a brief history of the evolution of the study of groundwater exchange with lakes, followed by a listing of the most commonly used methods for quantifying this exchange. Rates of exchange between lakes and groundwater compiled from the literature are statistically summarized for both exfiltration (flow from groundwater to a lake) and infiltration (flow from a lake to groundwater), including per cent contribution of groundwater to lake‐water budgets. Reported rates of exchange between groundwater and lakes span more than five orders of magnitude. Median exfiltration is 0.74 cm/day, and median infiltration is 0.60 cm/day. Exfiltration ranges from near 0% to 94% of input terms in lake‐water budgets, and infiltration ranges from near 0% to 91% of loss terms. Median values for exfiltration and infiltration as percentages of input and loss terms of lake‐water budgets are 25% and 35%, respectively. Quantification of the groundwater term is somewhat method dependent, indicating that calculating the groundwater component with multiple methods can provide a better understanding of the accuracy of estimates. The importance of exfiltration to a lake budget ranges widely for lakes less than about 100 ha in area but generally decreases with increasing lake area, particularly for lakes that exceed 100 ha in area. No such relation is evident for lakes where infiltration occurs, perhaps because of the smaller sample size. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Transit times of water under steady stormflow conditions in the Gårdsjön G1 catchment          下载免费PDF全文

Benny Selle  Holger Lange  Gunnar Lischeid  Michael Hauhs 《水文研究》2015,29(22):4657-4665

In this paper we report on a series of replicated tracer experiments with deuterium conducted under controlled, steady stormflow conditions at the Gårdsjön G1 catchment in south‐western Sweden. In five different years, these experiments were carried out in a subcatchment of G1. Deuterium was applied as a narrow pulse so that distributions of water transit times could be directly inferred from the observed tracer breakthrough curves. Significantly different transit times of water were observed under similar experimental conditions. Coefficients of variation for estimated mean transit times were greater than 60%, which can be understood as a measure of the interannual variability for this type of experiments. Implications for water transit times under more natural flow conditions as wells as for future experimentation are discussed. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

The role of technology for achieving climate policy objectives: overview of the EMF 27 study on global technology and climate policy strategies   总被引：3，自引：1，他引：2  

Elmar Kriegler  John P. Weyant  Geoffrey J. Blanford  Volker Krey  Leon Clarke  Jae Edmonds  Allen Fawcett  Gunnar Luderer  Keywan Riahi  Richard Richels  Steven K. Rose  Massimo Tavoni  Detlef P. van Vuuren 《Climatic change》2014,123(3-4):353-367

This article presents the synthesis of results from the Stanford Energy Modeling Forum Study 27, an inter-comparison of 18 energy-economy and integrated assessment models. The study investigated the importance of individual mitigation options such as energy intensity improvements, carbon capture and storage (CCS), nuclear power, solar and wind power and bioenergy for climate mitigation. Limiting the atmospheric greenhouse gas concentration to 450 or 550 ppm CO₂ equivalent by 2100 would require a decarbonization of the global energy system in the 21^st century. Robust characteristics of the energy transformation are increased energy intensity improvements and the electrification of energy end use coupled with a fast decarbonization of the electricity sector. Non-electric energy end use is hardest to decarbonize, particularly in the transport sector. Technology is a key element of climate mitigation. Versatile technologies such as CCS and bioenergy are found to be most important, due in part to their combined ability to produce negative emissions. The importance of individual low-carbon electricity technologies is more limited due to the many alternatives in the sector. The scale of the energy transformation is larger for the 450 ppm than for the 550 ppm CO₂e target. As a result, the achievability and the costs of the 450 ppm target are more sensitive to variations in technology availability.  相似文献   

Microplastics in oceans     

Zarfl C  Fleet D  Fries E  Galgani F  Gerdts G  Hanke G  Matthies M 《Marine pollution bulletin》2011,62(8):1589-1591

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Rings Around Planets, Atmospheric Superrotation, and Their Great Spots     

Wolfgang Kundt  Gunnar Lüttgens 《Astrophysics and Space Science》1997,257(1):33-47

A common explanation is offered of the facts that the (outer) planets Jupiter, Saturn, Uranus, and Neptune (i) have ring systems inside their magnetospheres, (ii) show alternating atmospheric super- and sub-rotation in latitude belts, and (iii) have great (coloured) whirling spots in their atmospheres, at latitudes of maximal shear flow. The common reason, so we argue, is the action of magnetic torques between the various ring systems in non-synchronous rotation which drive electric currents, help ionize the orbiting gas, and redistribute angular momentum. Very similar reasoning has been used earlier – though incorrect in detail – to explain the complicated system of torsional oscillations in the solar convection zone.  相似文献   

Arsenic in shallow groundwater of Bangladesh: investigations from three different physiographic settings   总被引：1，自引：0，他引：1  

M. Aziz Hasan  K. Matin Ahmed  Ondra Sracek  Prosun Bhattacharya  Mattias von Brömssen  Sandra Broms  Johan Fogelström  M. Lutful Mazumder  Gunnar Jacks 《Hydrogeology Journal》2007,15(8):1507-1522

Occurrences of arsenic (As) in the Bengal Basin of Bangladesh show close relationships with depositional environments and sediment textures. Hydrochemical data from three sites with varying physiography and sedimentation history show marked variations in redox status and dissolved As concentrations. Arsenic concentration in groundwater of the Ganges Flood Plain (GFP) is characteristically low, where high Mn concentrations indicate redox buffering by reduction of Mn(IV)-oxyhydroxides. Low DOC, \( {\text{HCO}}^{ - }_{3} \), \( {\text{NH}}^{ + }_{4} \) and high \( {\text{NO}}^{ - }_{3} \) and \( {\text{SO}}^{{2 - }}_{4} \) concentrations reflect an elevated redox status in GFP aquifers. In contrast, As concentration in the Ganges Delta Plain (GDP) is very high along with high Fe and low Mn. In the Meghna Flood Plain (MFP), moderate to high As and Fe concentrations and low Mn are detected. Degradation of organic matter probably drives redox reactions in the aquifers, particularly in MFP and GDP, thereby mobilising dissolved As. Speciation calculations indicate supersaturation with respect to siderite and vivianite in the groundwater samples at MFP and GDP, but groundwater in the GFP wells is generally supersaturated with respect to rhodochrosite. Values of log P_CO2 at MFP and GDP sites are generally higher than at the GFP site. This is consistent with Mn(IV)-redox buffering suggested at the GFP site compared to Fe(III)-redox buffering at MFP and GDP sites.  相似文献   

The effects of humic substances on the transport of radionuclides: Recent improvements in the prediction of behaviour and the understanding of mechanisms     

Nick D. Bryan  Liam Abrahamsen  Nick Evans  Peter Warwick  Gunnar Buckau  Liping Weng  Willem H. Van Riemsdijk 《Applied Geochemistry》2012

Some recent developments made during the European Union 6th Framework Integrated Project FUNMIG in the understanding and prediction of behaviour in ternary systems of radionuclides, humic substances and mineral surfaces are described. These developments are placed in the context of the existing literature. The aim is to describe the current understanding of humic substance mediated radionuclide transport as it may be applied to calculations in support of Radiological Performance Assessment. Some improvements in experimental techniques that provide the raw data to calibrate metal ion binding models are explained. The various metal ion binding models that are available are described and contrasted, before the recent development of ternary system models, in particular the Ligand Charge Distribution model that can predict metal ion and humic substance behaviour in ternary systems. The kinetic effects in ternary systems are described along with the models that are used to describe them. Finally, the remaining challenges in making predictions of radionuclide transport for the Radiological Performance Assessment of radioactive waste repositories are discussed.  相似文献   

The value of technology and of its evolution towards a low carbon economy   总被引：2，自引：1，他引：1  

Massimo Tavoni  Enrica De Cian  Gunnar Luderer  Jan Christoph Steckel  Henri Waisman 《Climatic change》2012,114(1):39-57

This paper assesses the economic value associated with the development of various low-carbon technologies in the context of climate stabilization. We analyze the impact of restrictions on the development of specific mitigation technologies, comparing three integrated assessment models used in the RECIPE comparison exercise. Our results indicate that the diversification of the carbon mitigation portfolio is an important determinant of the feasibility of climate policy. Foregoing specific low carbon technologies raises the cost of achieving the climate policy, though at different rates. CCS and renewables are shown to have the highest value, given their flexibility and wide coverage. The costs associated with technology failure are shown to be related to the role that each technology plays in the stabilization scenario, but also to the expectations about their technological progress. In particular, the costs of restriction of mature technologies can be partly compensated by more innovation and technological advancement.  相似文献   

Factors Controlling Total Concentration and Aqueous Speciation of Aluminium in an Acidic Headwater Stream of the Bavarian Forest National Park: a Modelling Approach     

Ingo Haag  Klaus Moritz  Jochen Bittersohl  Gunnar Lischeid 《洁净——土壤、空气、水》2001,29(4):206-218

The purpose of the present paper is to analyse factors controlling total concentration and aqueous speciation of aluminium in the Große Ohe River, using a thermodynamic equilibrium model and a mixing approach. A model compound for humic substances is derived on the basis of the relation between anion deficit and the organic carbon content in the river as well as literature data. An equilibrium speciation model for aluminium is set up, considering this model compound and relevant inorganic solutes. Although the model cannot be verified directly, its results may be viewed as qualitatively correct. Applying the model to measured stream water samples highlights that aqueous speciation of aluminium is mainly controlled by the pH value and discharge and that free aluminium concentrations reach clearly toxic levels during acidic episodes. Comparing measured concentrations of sulfate and H⁺ and calculated concentrations of Al³⁺ with solubility curves of gibbsite like minerals and jurbanite clearly shows that total aluminium concentrations are not controlled by equilibria with these mineral phases alone. The observed relationship can be better explained from a mixture of two distinct waters, representing lowflow and highflow chemistry, and the resulting equilibrium concentrations. This indicates that total aluminium concentration, in particular during high discharge events, is mainly controlled by the mixture of waters with differing chemistry and flowpaths.  相似文献