排序方式： 共有9条查询结果，搜索用时 296 毫秒
1
1.
Behaviour and dynamics of a hydrothermal plume in Lake Banyoles, Catalonia, NE Spain 总被引：1，自引：0，他引：1
TERESA SERRA† MARIANNA SOLER RAMON JULIÀ‡ XAVIER CASAMITJANA JORDI COLOMER† 《Sedimentology》2005,52(4):795-808
A hydrothermal plume forms in Lake Banyoles, NE Spain, as a result of convection above a springwater-fed suspension cloud ponded on the lake floor. The plume propagates upwards reaching a level of neutral buoyancy from where a turbidity current spreads out laterally. Two-dimensional temperature and particle concentration measurements show the fate of the hydrothermal plume and its associated turbidity current and reveal its seasonal development. Silt particles transported by the plume have been used as tracers to determine the maximum and equilibrium heights of the plume. When the lake is stratified, the vertical transport of sediment is confined to the lake hypolimnion, as the thermocline limits the vertical propagation of the plume. In contrast, when the lake water column is mixed, the plume reaches the surface of the lake. The field measurements have been compared with models for thermal convection from finite isolated sources. Measurements of the flow velocity at the source of the hydrothermal plume (i.e. the rim current velocity) indicate that cold hypolimnetic water is entrained by the plume. Sedimentation rates measured from sediment traps at the zone where the turbidity current develops vary between 10 and 25 g m−2 day−1, and result from continuous silt particle sedimentation from the turbidity current. Sedimentation rates in traps are higher for stations situated close to the source than those further away (<5 g m−2 day−1). Moreover, the results demonstrate that double diffusive sedimentation from the turbidity current was dominant over grain-by-grain settling, causing a mixed distribution of sediments in the region where the turbidity current spreads. The deposition of silt particles could explain the occurrence of silt layers interbedded with biocalcarenites in the littoral zones of the lake and the stratigraphy identified by seismic profiles and cores taken from the lake floor. 相似文献
2.
3.
Abstract— The reaction between kamacite grains and H2 + CO gas mixture has been tested in the laboratory under experimental conditions presumed for interplanetary dust particle (IDP) formation in a nebular-type environment (H2:CO = 250:1; 5 × 10?4 atm total pressure, and 473 K). Carbon deposition, hydrocarbon production in the C1–C4 range, and the formation of an ?-carbide phase occur when well-defined model FeNi bcc alloy (kamacite) particles are exposed to a mixture of H2 + CO during 103 h. These results strongly support the idea that gas-solid reactions in the solar nebula during CO hydrogenation represent a plausible scenario for the formation of carbides and carbonaceous materials in IDPs, as well as for the production of hydrocarbons through Fischer-Tropsch-type reactions. 相似文献
4.
5.
6.
Biochronological data inferred from the Early Pleistocene small mammals of the Barranc de la Boella site (Tarragona,north‐eastern Spain) 
下载免费PDF全文
下载免费PDF全文 7.
8.
9.
Abstract— Detailed laboratory studies have been carried out in order to simulate the interaction between nanometer‐sized kamacite metal particles and different gas mixtures consisting of H2:H2S (250:0.1), H2:CO (250:1), and H2:CO:H2S (250:1:0.1) under nebular‐type conditions (5 × 10?4 atm and 473 K). Reaction of H2 + H2S with kamacite particles for 1000 h leads to the formation of pyrrhotite. Incorporation of CO into the gaseous reactant mixture results in the formation of both sulfide and carbide phases. At the same time, amorphous C is deposited onto the metal particles and organic molecules are evolved, namely hydrocarbons and thiols in the C1‐C5 and C1‐C2 range, respectively. Carbon deposition and production of organics are enhanced with respect to experiments performed with H2 + CO, where a carbide phase is formed. There is no evidence for the existence of S‐poisoning effects on the metal‐catalysed hydrogenation of CO through Fischer‐Tropsch‐type reactions in nebular environments. In fact, it is experimentally demonstrated that S‐containing organic species could be synthesized by such reactions from nebular gas. 相似文献
1