Water flow path interactions with soil hydraulic properties in till soil at Gårdsjön, Sweden     

Lars Nyberg 《Journal of Hydrology》1995,170(1-4):255-275

In 1989, in a hydrological research programme within a deacidification project in the Gårdsjön area in southwest Sweden, flow paths and residence times of soil water and groundwater in microcatchments were examined to support the interpretation of the hydrochemical changes. Saturated hydraulic conductivity and soil water retention were analysed on more than 100 cylinder samples. The catchments have shallow sandy-silty till soil with a mean depth in the main catchment of 43 cm. Porosity of the mineral soil in the main catchment was high and ranged from 38 to 85%. The samples from the B-horizon had generally higher porosity. Porosity and the content of organic matter were correlated. The soil water retention was relatively high at all tensions, likely owing to the high content of organic matter. Dissolved organic substances were most probably transported from the shallow soil on the steep sides of the catchment down to the valley where it precipitated. The high porosities could be a consequence of long-term weathering, provided that the organic substances present have increased the leaching of the weathering products. Measured values of saturated hydraulic conductivity were close to log-normally distributed with a mean for all samples of 3 × 10⁻⁵ m s⁻¹. There was a significant increase in conductivity toward the ground surface with the mean conductivity of the samples in the uppermost 10 cm of the mineral soil of 4 × 10⁻⁵ m s⁻¹, which was about 13 times higher than the conductivity of 3 × 10⁻⁶ m s⁻¹ at 1 m depth. From the relationship between runoff at the catchment outlet and groundwater levels, the conductivity was estimated to be 15–200 times higher in the upper soil layer than in the deeper ones. In one profile, 44–64% of the yearly lateral flow was estimated to occur above 30 cm depth. The conductivity was correlated with the content of drainable water, which indicated the importance of the largest pores for the saturated hydraulic conductivity.  相似文献   

Towards knowledge-based geovisualisation using Semantic Web technologies: a knowledge representation approach coupling ontologies and rules     

Weiming Huang  Lars Harrie 《International Journal of Digital Earth》2020,13(9):976-997

ABSTRACT

Geovisualisation is a knowledge-intensive art in which both providers and users need to possess a wide range of knowledge. Current syntactic approaches to presenting visualisation information lack semantics on the one hand, and on the other hand are too bespoke. Such limitations impede the transfer, interpretation, and reuse of the geovisualisation knowledge. In this paper, we propose a knowledge-based approach to formally represent geovisualisation knowledge in a semantically-enriched and machine-readable manner using Semantic Web technologies. Specifically, we represent knowledge regarding cartographic scale, data portrayal and geometry source, which are three key aspects of geovisualisation in the contemporary web mapping era, coupling ontologies and semantic rules. The knowledge base enables inference for deriving the corresponding geometries and portrayals for visualisation under different conditions. A prototype system is developed in which geospatial linked data are used as underlying data, and some geovisualisation knowledge is formalised into a knowledge base to visualise the data and provide rich semantics to users. The proposed approach can partially form the foundation for the vision of web of knowledge for geovisualisation.  相似文献   

Baltic Sea Level project with GPS     

Ming Pan  Lars E. Sjöberg 《Journal of Geodesy》1993,67(1):51-59

In order to study the Baltic Sea Level change and to unify national height systems a two week GPS campaign was performed in the region in Autumn 1990. Parties from Denmark, Finland, Germany, Poland and Sweden carried out GPS measurements at 26 tide gauges along the Baltic sea and 8 VLBI and SLR fiducial stations with baseline lengths ranging from 230 km to 1600 km. The observations were processed in the network mode with the Bernese version 3.3 software using orbit improvement techniques. To get rid of the scale error introduced by the ionospheric refraction from single-frequency data, the local models of the ionosphere were estimated using L4 observations. The tropospheric zenith corrections were also considered. The preliminary results show average root mean square (RMS) errors of about ±3 cm in the horizontal position and ±7 cm in the vertical position relative to the Potsdam SLR station in ITRF89 system. After transformation of the GPS results to geoid heights using the levelled heights, an absolute comparison with gravimetric geoid heights using the least squares modification of Stokes' formula (LSMS), the modified Molodensky and the NKG Scandinavian geoid 1989 (NGK-89) models gives a standard deviation of the difference of ±7cm to ±9cm for the NKG-89 model and of ±9cm to ±30cm for the LSMS and the modified Molodensky model. The Swedish height system is found to be about 8-37cm higher than those of the other Baltic countries for NKG-89 model.  相似文献   

New challenges for the international management of ocean resources     

Jan Henry T. Olsen 《Marine pollution bulletin》1994,29(6-12):262-265

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Cristobalite-pyroxene in an L6 chondrite: implications for metamorphism     

Edward J. Olsen  Toshiko K. Mayeda  Robert N. Clayton 《Earth and Planetary Science Letters》1981

CRISPY is a cristobalite-pyroxene assemblage in the L6 chondrite ALHA 76003. It was formed by reaction of a very siliceous inclusion with the surrounding olivine-rich rock. Oxygen isotopes show that the inclusion was derived from a source with non-chondritic isotopic composition. The isotopes also show that the oxygen of the pyroxene reaction product was derived by simple mixing of oxygen from the inclusion and its immediately adjacent surroundings, with exchange with the bulk meteorite limited to a distance of about a millimeter. The persistence of cristobalite in close proximity to olivine, and the lack of isotopic equilibration, show that the metamorphic processes that form petrographic grade 6 chondrites involve transport of major elements over distances only on the order of millimeters.  相似文献   

Zooplankton in the Baltic Sea     

Lars Hernroth 《Marine pollution bulletin》1981,12(6):206-209

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A recurrence relation for the βn-function     

Lars Sjöberg 《Journal of Geodesy》1980,54(1):69-72

A recurrence relation is presented for the smoothing function, β_n, which is used in geodesy to relate spherical harmonics to their mean values over circular areas (caps). The proposed formula does not require the computation of the Legendre's polynomials. Moreover, it is numerically more stable than the formulas ofPellinen (1969) andMeissl (1971).  相似文献   

Study of peristerites using transmission electron microscopy and energy dispersive X-ray analysis     

Arne Olsen 《Contributions to Mineralogy and Petrology》1975,51(4):297-302

Peristerite feldspars from Seiland in Norway have been studied by a combination of transmission electron microscopy and energy dispersive X-ray analysis. The different types of microtextures have been correlated with the local mean composition, and it is found that the miscibility gap between An₄ and An₁₇ extends into the ternary Or—Ab—An region. The orientation of the more common type of exsolution lamellae varies from (08¯1) to about (¯1, 21, ¯2) with increasing potassium content.  相似文献   

Mineralogy and petrology of silicate inclusions in iron meteorites     

T. E. Bunch  Klaus Keil  E. Olsen 《Contributions to Mineralogy and Petrology》1970,25(4):297-340

Silicate inclusions in 17 iron meteorites have been analyzed by the electron microprobe and classified, according to their phase assemblages, compositions, and textures, into three major types: Odessa, Copiapo, and Weekeroo Station, and three miscellaneous types: Enon, Kendall County, and Netschaëvo. Phase compositions in both Odessa- and Copiapo-type inclusions are very similar, but the two types are different in texture and constituent phases. Weekeroo Station-type inclusions are very different in every respect from other inclusions.For Odessa- and Copiapo-type inclusions, the distribution coefficients of Fe²⁺ and Mg in coexisting orthopyroxene and clinopyroxene indicate equilibration temperatures of 1,000° C, and the Ca/(Ca+Mg) ratios indicate temperatures of 900° C to 1,000° C. Equilibration temperatures determined for chromite-olivine pairs have a higher range of 1,154° C to 1,335° C. Minor element distributions among coexisting ferromagnesian silicates in these inclusions follow consistent patterns and are constant for any given sample, suggesting equilibrium assemblages. Major and minor element distributions for Weekeroo Station inclusions are anomalous, indicating nonequilibrium.Compositional data, the fragmentary shapes of many inclusions, the highly differentiated characteristic of two types of inclusions, the apparent disequilibrium between kamacite in inclusions and kamacite of the iron host, and the relict chondrules found in Netschaëvo suggest that many of the inclusions did not form cogenetically with the iron host, but represent pre-existing stony material that was taken up by an iron melt, probably not in the core of the parent body (or bodies).  相似文献   

Core surface flow modelling from high-resolution secular variation     

R. Holme  N. Olsen 《Geophysical Journal International》2006,166(2):518-528

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