Redox Processes in Groundwater Impacted by Landfill Leachate   总被引：6，自引：0，他引：6  

Leif Basberg  David Banks  Ola M. Sæther 《Aquatic Geochemistry》1998,4(2):253-272

Groundwater downgradient from Trandum municipallandfill was investigated in summer 1996, with a viewto assessing the distribution of redox-sensitivespecies. The water table at Trandum is 10–26 metersbelow the surface. Monitoring well filters have beeninstalled at depths of up to 15 m below water table,covering an area of 400 m by 200 m. Groundwaterinfluenced by the landfill seems to be confined tothis area. Pristine groundwater has a chemicalsignature indicative of calcite and pyrite weathering.Groundwater influenced by leachate from the landfillexhibits an excess of alkalinity relative to calcium,which is likely to be derived from degradation oforganic matter in the landfill. Groundwaterimmediately below and downstream of the landfillcontains elevated concentrations of Fe and Mn, largelymobilized under reducing conditions from the aquifermatrix and reflected in depleted HNO₃-extractable Feand Mn in sediment samples from the same area.Groundwater samples allow the tentative identificationof redox zones based on oxidized and reduced forms ofFe, Mn, N and S. A methanogenic zone is notobserved.  相似文献   

Genetic and ecological effects of salmon farming on wild salmon: modelling from experimental results     

Hindar  Kjetil; Fleming  Ian A.; McGinnity  Philip; Diserud  Ola 《ICES Journal of Marine Science》2006,63(7):1234-1247

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Fishing vessel profitability and local economic link obligations—the case of Norwegian trawlers     

Ola Flaaten  Knut Heen 《Marine Policy》2004,28(6):1154

This paper investigates to what extent limited entry licence local-link obligations hamper economic performance of Norwegian wet fish trawlers. For 1999 average landing prices, gross revenue, net profit and some other economic indicators are compared for three groups of trawlers: (A) vessels that had local-link licence obligations and complied with them; (B) vessels that had such obligations but did not comply; and (C) vessels without local-link obligations. Average operating profit was highest for Group C. Group B vessels’ operating profit was just above that of Group A, despite significantly higher revenues. For all fish species, except redfish, Group C trawlers received higher prices than the other vessels.  相似文献   

Near-Surface Vertical Flux Divergence in the Stable Boundary Layer     

L. Mahrt  Christoph K. Thomas  Andrey A. Grachev  P. Ola G. Persson 《Boundary-Layer Meteorology》2018,169(3):373-393

Flow in the stable boundary layer is examined at four contrasting sites with greater upwind surface roughness. The surface heterogeneity is disorganized and in some cases weak as commonly occurs. With low wind speeds, the vertical divergence (or convergence) of the momentum and heat fluxes can be large near the surface in what is normally assumed to be the surface layer where such divergence is neglected. For the two most heterogeneous sites, a shallow “new” boundary layer is captured by the tower observations, analogous to an internal boundary layer but more complex. Above the new boundary layer, the magnitudes of the downward fluxes of heat and momentum increase with height in a transition layer, reach a maximum, and then decrease with height in an overlying regional boundary layer. Similar structure is observed at the site with rolling terrain where the shallow new boundary layer at the surface is identified as cold-air drainage generated by the local slope above which the flow undergoes transition to an overlying regional flow. Significant flux divergence near the surface is generated even over an ice floe for low wind speeds and in a shallow Ekman layer that forms during the polar night. For higher wind speeds, the magnitude of the downward fluxes decreases gradually with height at all levels as in a traditional boundary layer.  相似文献   

Atmospheric response to the autumn sea-ice free Arctic and its detectability   总被引：1，自引：0，他引：1  

Lingling Suo  Yongqi Gao  Dong Guo  Jiping Liu  Huijun Wang  Ola M. Johannessen 《Climate Dynamics》2016,46(7-8):2051-2066

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Cyber Literacy for GIScience: Toward Formalizing Geospatial Computing Education     

Eric Shook  Forrest J. Bowlick  Karen K. Kemp  Ola Ahlqvist  Patricia Carbajeles-Dale  David DiBiase 《The Professional geographer》2019,71(2):221-238

The unprecedented availability of geospatial data and technologies is driving innovation and discovery but not without the risk of losing focus on the geographic foundations of space and place in this vast “cyber sea” of data and technology. There is a pressing need to educate a new generation of scientists and citizens who understand how space and place matter in the real world and who understand and can keep pace with technological advancements in the computational world. We define cyberliteracy for GIScience (cyberGIScience literacy) and outline eight core areas that serve as a framework for establishing the essential abilities and foundational knowledge necessary to navigate and thrive in this new technologically rich world. The core areas are arranged to provide multiple dimensions of learning ranging from a technological focus to a problem solving focus or a focus on GIScience or computational science. We establish a competency matrix as a means of assessing and evaluating levels of cyberGIScience literacy across the eight core areas. We outline plans to catalyze the collaborative development and sharing of instructional materials to embed cyberGIScience literacy in the classroom and begin to realize a cyberliterate citizenry and academe. Key Words: big data, computational thinking, geographic education, GIS, spatial thinking.  相似文献   

Greenland Ice Sheet Elevation Change in Winter and Influence of Atmospheric Teleconnections in the Northern Hemisphere          下载免费PDF全文

CHEN Lin-Ling  Ola M. JOHANNESSEN  Kirill KHVOROSTOVSKY  WANG Hui-Jun 《大气和海洋科学快报》2009,2(6):376-380

The relationship between the variability of the surface elevation of the Greenland Ice Sheet （GIS） in winter and sea level pressure is identified through analysis of data from satellite-borne radar altimeters, together with meteorological data fields during 1993-2005. We found that both the North Pacific Oscillation （NPO） and the North Atlantic Oscillation （NAO）, the two major teleconnection patterns of the atmospheric surface pressure fields in the Northern Hemisphere, significantly influence the GIS winter elevation change. Further, it is suggested that the NPO may affect the GIS accumulation by influencing the NAO, particularly by changing the intensity and location of the Icelandic Low.  相似文献   

Interaction Between the Warm Subsurface Atlantic Water in the Sermilik Fjord and Helheim Glacier in Southeast Greenland     

Ola M. Johannessen  Alexander Korablev  Victoria Miles  Martin W. Miles  Knut E. Solberg 《Surveys in Geophysics》2011,32(4-5):387-396

Recent observations of ocean temperature in several Greenland fjords suggest that ocean warming can cause large changes in the outlet glaciers in these fjords. We have observed the Helheim outlet-glacier front in the Sermilik Fjord over the last three decades using satellite images, and the vertical fjord temperature and salinity during three summer expeditions, 2008?C2010. We show that the subsurface water below 250 m depth is the warm saline Atlantic Water from the Irminger Sea penetrating into the fjord and exposing the lower part of the Helheim glacier to warm water up to 4°C. Lagged correlation analysis spanning the 30-year time series, using the subsurface Atlantic Water temperature off the coast as a proxy for the variability of the subsurface warm Atlantic Water in the fjord, indicates that 24% of the Helheim ice-front movement can be accounted for by ocean temperature. A strong correlation (?C0.75) between the ice-front position and the surface air temperature from a nearby meteorological station suggests that the higher air temperature causes melting and subsequent downward percolation of meltwater through crevasses leading to basal lubrication; the correlation accounts for 56% of the ice-front movement. The precise contribution of air temperature versus ocean temperature however, remains an open question, as more oceanographic and meteorological measurements are needed close to the glacier terminus.  相似文献   

Book Review Forum—Learning the City with Colin Mcfarlane     

Neil M. Coe  Ananya Roy  Kevin Ward  Andrew Harris  Ola Söderström  Tim Bunnell 《Urban geography》2013,34(1):131-150

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Rough classification and accuracy assessment     

Ola Ahlqvist  Johannes Keukelaar  Karim Oukbir 《International journal of geographical information science》2013,27(5):475-496

In search for methods to handle imprecision in geographical information this paper explores the use of rough classification to represent uncertainty. Rough classification is based on rough set theory, where an uncertain set is specified by giving an upper and a lower approximation. Novel measures are presented to assess a single rough classification, to compare a rough classification to a crisp one and to compare two rough classifications. An extension to the error matrix paradigm is also presented, both for the rough-crisp and the roughrough cases. An experiment on vegetation and soil data demonstrates the viability of rough classification, comparing two incompatible vegetation classifications covering the same area. The potential uses of rough sets and rough classification are discussed and it is suggested that this approach should be further investigated as it can be used in a range of applications within geographic information science from data acquisition and analysis to metadata organization.  相似文献