排序方式： 共有37条查询结果，搜索用时 15 毫秒
31.
In this study the chemical composition of seston, transported by tidal water between an estuarine salt marsh and the adjacent water system, was assessed. The analytical techniques used are Pyrolysis in combination with Gas Chromatography and/or Mass Spectrometry. Interpretation of the Py-MS data was aided by discriminant analysis.The presented results indicate that throughout the year a dominant refractory fraction is present in the seston, but that seasonal additions can be distinguished. Apart from this seasonal pattern, differences between ebb and flood can be visualized by the use of discriminant analysis. During summertime, flood seston is enriched with lipids and recently synthesized polysaccharides, while during the rest of the year the flood tide samples contain more (remains of) lignin and polysaccharides than their ebb tide counterparts. The lignin markers comprise only fragments with extremely altered (reduced) character.These results, which highlight the molecular composition of the exchanged seston but do not offer exact quantitative budget estimations, provide no evidence for export of lignin-rich particulate halophytic material from the marsh to the water system. On the contrary, based on seston compositions, the water system seems to supply lignin-rich particles to the marsh during a considerable part of the year. 相似文献
32.
33.
Prof. Dr. F. Scheffer B. Meyer U. Babel 《Contributions to Mineralogy and Petrology》1959,6(6):371-387
Zusammenfassung Die Arbeit befaßt rich mit der Bestimmungsmöglichkeit der Eisenoxydmodifikationen in Böden — speziell des Lepidokrokits — mit Hilfe magnetischer Messungen. Einleitend wird ein Überblick über magnetische Grundgrößen und die Faktoren, die das ferromagnetische Verhalten beeinflussen, gegeben. Eine einfache Meßapparatur wird beschrieben and die Meßgenauigkeit diskutiert. Zur quantitativen Abschätzung von Lepidokrokitgehalten wird näher auf die Entstehung der Auftriebsgrößen, die Herstellung von Eichsubstanzen und die in Frage kommenden Umwandlungstemperaturen eingegangen. Für die Erhitzung von Böden wird eine Arbeitsmethode entwickelt. Ferner wird die dabei mögliche Entstehung ferromagnetischer Stoffe lurch anwesende organische Substanz behandelt. Die Grenzen and Möglichkeiten der Methode werden diskutiert und Beispiele von Messungen an Böden gebracht. 相似文献
34.
35.
36.
On November 28, 2003, at about 00:30 PST, 35 km east of Prince Rupert in northwestern British Columbia, an extremely rapid, retrogressive liquefaction earth flow, or a clay flow-slide, severed the natural gas pipeline. As a result, Prince Rupert residents were without natural gas heat for 10 days. The landslide has a steep main scarp that is 45 m high by 345 m wide. It consists of glaciomarine sediments mantled by rubbly colluvium lying on, and against smooth bedrock of the valley wall. It covers an area of 32 ha, and displaced about 4.7 M m3 of material. This displaced material flowed up and down river over a distance of 1.7 km, blocked the river, and caused flooding upstream for a distance of 10 km. This landslide is the most recent of four large landslides that have occurred over the last four decades in glaciomarine sediments in northwestern British Columbia. 相似文献
37.
Terrain stability mapping on British Columbia forest lands: an historical perspective 总被引：1，自引：0，他引：1
Land management associated with forest practices in British Columbia (BC) over the last three decades has led to the development
of terrain stability hazard mapping. Terrain stability mapping (TSM) in BC originated in the early 1970s, when forest harvesting
was progressing from valley bottoms onto steep, unstable terrain, which led to an increase in harvesting- and road-related
landslides. Since then TSM methods have been evolved. Beginning in the early 1970s, terrain hazards were incorporated into
the forest inventory classification system to delineate environmentally sensitive areas for land-use planning. By 1974, operational
terrain stability maps were introduced by the MacMillan Bloedel forest company on the Queen Charlotte Islands. In the 1980s,
this method was adopted by other forest companies and government agencies along the BC coast and then extended to the BC interior
in the 1990s. The system was refined over time, based on new knowledge and on the introduction of mapping standards, including
standards for capture and presentation of digital maps. In 1995, reconnaissance terrain stability mapping and detailed terrain
stability mapping were formalized with three and five hazard classes, respectively. More recently, qualitative and semi-quantitative
approaches to predict landslide occurrence based on terrain and landslide inventories have been incorporated into the techniques
for TSM. 相似文献