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排序方式: 共有110条查询结果,搜索用时 15 毫秒
61.
Hans-Christian Teien Brit Salbu Frode Kroglund Lene Sørlie Heier Bjørn Olav Rosseland 《Applied Geochemistry》2007
Cationic Al species (Ali) cause toxic effects towards fish in acidified water. As several factors can influence the Ali-speciation, acid neutralising capacity (ANC) has been applied as an alternative indicator for acidification and effects towards fish. However, the critical range of ANC for biological stress has been shown to be dependent upon the concentration of organic material (DOC). Using in situ size fractionation techniques the influence of particulate and colloidal DOC (0–400 μM) on Ali-speciation and ANC-values was investigated in Norwegian streams. During high flow events with high river transport of DOC the Ali concentration increased by a factor of 2 due to retention of colloidal Al species (>10 kDa), probably organic, in the chromatography column. Ultrafiltration (?10 kDa) of water prior to chromatography reduced the influence of non-toxic organic Al-species, on Ali-speciation. The charge balanced ANC-values (ANCcb) were also significantly lower (on average 34 μeq L−1) in ultrafiltered water compared to unfiltered water samples, as base cations were associated with colloidal DOC (>10 kDa to 0.45 μm) and organic acids were not incorporated in the ANCcb estimate. Thus, ANCcb will underestimate the acidification effects towards fish in organic waters increasing with concentration of colloidal DOC present. Alkalinity based ANC-values (ANCalk), which include a fraction of organic acids, were similar in unfiltered and ultrafiltered waters, but higher than ANCcb-values of ultrafiltered samples. Thus, ANCalk-values also underestimate the acidification effects on fish in organic waters. Based on ultrafiltered samples, however, ANCcb-values was negatively correlated with Ali independent of the DOC present and thus a more correct indicator for toxic Al-species. 相似文献
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Christopher Harman Kevin V. Thomas Knut Erik Tollefsen Sonnich Meier Olav Byum Merete Grung 《Marine pollution bulletin》2009,58(11):1671-1679
In order to assess the environmental impact of aquatic discharges from the offshore oil industry, polar organic chemical integrative samplers (POCIS) and semipermeable membrane devices (SPMDs) were deployed around an oil platform and at reference locations in the North Sea. Exposure to polycyclic aromatic hydrocarbons (PAH) and alkylated phenols (AP) was determined from passive sampler accumulations using an empirical uptake model, the dissipation of performance reference compounds and adjusted laboratory derived sampling rates. Exposure was relatively similar within 1–2 km of the discharge point, with levels dominated by short chained C1–C3 AP isomers (19–51 ng L−1) and alkylated naphthalenes, phenanthrenes and dibenzothiophenes (NPD, 29–45 ng L−1). Exposure stations showed significant differences to reference sites for NPD, but not always for more hydrophobic PAH. These concentrations are several orders of magnitude lower than those reported to give both acute and sub-lethal effects, although their long term consequences are unknown. 相似文献
64.
Massive, transient late syn-rift-to-breakup volcanism during separation between the Seychelles microcontinent and India formed the Deccan continental flood basalts and their equivalents on the Seychelles-Mascarene Plateau and on the conjugate continental margins, i.e. the Deccan Large Igneous Province. We estimate an original extrusive area of at least 1.8×106 km2, and a volume >1.8×106 km3, and suggest a plate tectonic model comprising: (1) development of the Seychelles microplate by fan-shaped spreading in the Mascarene Basin, and continental extension followed by fan-shaped spreading between India and the Seychelles during A29-27 time. (2) Cessation of fan-shaped spreading just after A27 time, followed by spreading along the India-Seychelles plate boundary. (3) Margin subsidence, modified south of Goa by the persistent, time-transgressive effects along the plume trail. The margin is divided into three regional provinces by the prolongation of regional transforms which formed the east and west boundaries of the Seychelles microplate during breakup and early sea floor spreading. In some aspects, the conjugate margins are different from other volcanic margins; e.g. regional wedges of seaward dipping reflectors along the continent-ocean transition have not yet been reported. We ascribe this to the eruption of the most voluminous lavas during chron 29r, i.e on continental lithosphere in a late syn-rift setting. The enigmatic Laxmi Ridge is a complex marginal high comprised of both continental and oceanic crust. It was probably created during breakup, but may have experienced later magmatic and/or tectonic deformation. 相似文献
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Grete Stokstad Svein Olav Krøgli Wenche E. Dramstad 《Norsk geografisk tidsskrift. Norwegian journal of geography》2020,74(2):111-122
ABSTRACT Efficiency in agricultural food production has long been in focus and this has affected the spatial structure of agricultural land use. One outcome has been extensive criticism based on a wide range of negative consequences, such as for biodiversity, accessibility, cultural heritage, and aesthetics. In line with the European Landscape Convention (ELC), management of people’s everyday landscapes is important. In Norway, agricultural landscapes are the ‘everyday landscape’ for a large proportion of the population. The aim of the article is to contribute to the understanding of landscape changes perceived as positive or negative by the inhabitants. The authors focused on grain-crop dominated landscapes and the impact of smaller non-crop elements on people’s landscape preferences. They administered a photo-based questionnaire using manipulated photos to assess preferences for different agricultural landscapes. Additionally, people’s perceived objectives for the agricultural sector and agriculture’s primary functions were assessed. The results documented positive perceptions of added landscape elements and that people were both aware of and agreed on the multifunctional role of agriculture. The authors conclude that if the public’s preferences are to be taken into consideration, such as during policymaking, it is important to maintain various landscape elements in the large-scale grain field landscapes of Norway. 相似文献
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69.
Jan Chr. Blankenburgh Bj⊘rn A. Fossum Per A. Østerholt Hans Olav Torsen 《Marine Geodesy》2013,36(2):125-145
The hitherto promising finds of oil and gas on the Norwegian continental shelf have increased the general activity in this area considerably. Consequently, the need for better charts and more precise navigational systems have become more pertinent. During the past few years a number of marine geodetic projects have either been planned or embarked upon by various organizations within both the public and private sectors. This article gives a brief review of the Norwegian projects which have special relevance to marine geodesy; this includes the following areas: recommendations, requirements, precision navigation, satellite positioning, reference systems, boundary problems, bathymetry, geological mapping, marine geoid determination, and data base developments. The reference list will give the reader more detailed sources of information. 相似文献
70.
An approach is developed to estimate pore‐pressure changes in a compacting chalk reservoir directly from time‐lapse seismic attributes. It is applied to data from the south‐east flank of the Valhall field. The time‐lapse seismic signal of the reservoir in this area is complex, despite the fact that saturation changes do not have an influence. This complexity reflects a combination of pressure depletion, compaction and stress re‐distribution throughout the reservoir and into the surrounding rocks. A simple relation is found to link the time‐lapse amplitude and time‐shift attributes to variations in the key controlling parameter of initial porosity. This relation is sufficient for an accurate estimation of pore‐pressure change in the inter‐well space. Although the time‐lapse seismic estimates mostly agree with reservoir simulation, unexplained mismatches are apparent at a small number of locations with lower porosities (less than 38%). The areas of difference between the observations and predictions suggest possibilities for simulation model updating or a better understanding of the physics of the reservoir. 相似文献