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Cristina Iuga C. Ignacio Sainz-Díaz Annik Vivier-Bunge 《Geochimica et cosmochimica acta》2010,74(12):3587-12246
Clay particles are present in large quantities in mineral dust of atmospheric aerosols, and their interaction with organic species may influence atmospheric reactions and the prediction of environmental risks. However, the kinetics and mechanisms of adsorption and reaction of atmospheric volatile organic compounds on aerosol surfaces are not well understood.In this work, quantum chemical methods are used to study the adsorption of C2-C5 aliphatic aldehydes on silicate clusters active sites, and their subsequent reaction with OH radicals. It is shown that adsorption may occur in two different ways, and that the adsorption complex structure determines the subsequent path of its reaction with OH. The initial step in the OH reaction with acetaldehyde occurs according to the same mechanism as in the gas phase, i.e., the aldehydic hydrogen abstraction. Starting from propanal, another abstraction channel becomes increasingly important, involving mainly the abstraction of a β-hydrogen of the aliphatic chain. In the presence of a silica monomer model surface, the reaction rate of aldehydes with OH free-radicals is smaller than in the gas phase. Furthermore silicates are good sinks for trapping these aldehydes. Thus, our results may have implications in the study of tropospheric chemistry and cosmochemistry. 相似文献
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The continental margin off the Lofoten-Vesterålen islands between 67° and 70°N becomes progressively narrower northwards. The continental shelf west of the islands and in the Vestfjord is underlain by a relatively thin sedimentary sequence which has been subjected to block faulting, forming local basins and highs. The structural deformation had ceased in the mid-Creataceous. The Tertiary sediments are generally missing, but reappear in the Træn Basin south of about 67.5°N. The continental margin seaward of the shelf edge changes structural style from south to north. In the north, the marginal subsidence is characterized by major faults, whereas minor faults and flexuring dominate south of 69°N. A smooth acoustic basement reflector, which in places is underlain by dipping sub-basement interfaces, is typical for the area between anomaly 23 and the Vøring Plateau Escarpment. In the northern area, the acoustic basement extends almost to the shelf edge. These observations relate to the early Tertiary history of rifting and passive margin formation within a preexisting epicontinental sea between Norway and Greenland. The abrupt change from continental to oceanic basement is defined by the extension of the Vøring Plateau Escarpment south of 69.1°N and by the change in magnetic character off Vesterålen. 相似文献
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Heat flow taken between Svalbard and Greenland reveal three thermal provinces:
- 1. (1) the Molloy Ridge within the Spitsbergen Transform,
- 2. (2) the Yermak Plateau
- 3. (3) the northeastern margin of Svalbard (Nordaustlandet).
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Analysis of multichannel seismic data from the continental margin off Svalbard between the Senja and Spitsbergen fracture zones suggests that the transition between continental and oceanic crust is located at or close to the Hornsund Fault Zone. In the Late Paleocene/Early Eoeene (57 m.y.) the region between Svalbard and Northeast-Greenland was subjected to regional shear movements associated with a transform system between the young Lofoten-Greenland Basin and the Arctic Ocean. Approximately 50 m.y. ago the spreading axis migrated to the northeast creating a deep basin north of the Greenland-Senja Fracture Zone forming the passive margin between Bear Island and 76.5°N. North of 76.5°N the regional transform was maintained. At the time of the main reorganization of relative plate motion (36 m.y.) the northern margin evolved. A continental fragment was possibly cut off from the Svalbard margin forming a small microcontinent. The microcontinent appears as the submarine ridge which has been associated with the Hovgaard Fracture Zone. It is suggested that the sediments west of the Hornsund Fault Zone are not older than Eocene in the south and mid-Oligocene in the north. The position of the spreading axis has greatly influenced the margin sedimentation. 相似文献
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