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161.
162.
Sediment resuspension in two adjacent shallow coastal lakes: controlling factors and consequences on phosphate dynamics 总被引:1,自引:0,他引:1
Inmaculada de Vicente Luis Cruz-Pizarro Francisco J. Rueda 《Aquatic Sciences - Research Across Boundaries》2010,72(1):21-31
A combination of field measurements, modelling and laboratory experiments was used to evaluate the potential impact of sediment
resuspension on phosphorus (P) dynamics. The study was carried out in two adjacent shallow coastal lakes (Lake Honda and Lake
Nueva) which, due to their geographic proximity (only 200 m apart), are subject to equal meteorological forcing and represent
ideal systems to study how morphometry and sediment properties relate to wind events. The focusing factors (a measure of the
fluxes of sediment into the water column through resuspension) estimated by comparing settling fluxes measured in surface
sediment traps with those measured in bottom traps, were significantly larger (approximately 34% larger) in Lake Honda (LH;
1.18) than in Lake Nueva (LN; 0.88). Our model estimates of resuspension fluxes (E) were also ca. 40% larger in LH than in LN, in agreement with the observed focusing factors. The larger resuspension fluxes
encountered in LH, in comparison with LN, can mainly be explained by differences in lake morphometry. Still, they could arise
from differences in grain size distribution or in benthic algae concentration encountered in the lake sediments. By means
of adsorption experiments in the laboratory, we show that resuspension events will have different effects on P-dynamics in
LH and LN. While the resuspended material from LH tends to adsorb phosphate (PO4
3−), removing it from the water column, in LN the resuspended sediments tend to increase the availability of PO4
3− in solution. These differences arise from (1) higher concentrations of PO4
3− in water in LH compared to LN; and (2) larger PO4
3−adsorption capacity of the LH sediments as a result of the more abundant iron oxyhydroxides and clay. 相似文献
163.
Jordan Van Aalsburg John B. Rundle Lisa B. Grant Paul B. Rundle Gleb Yakovlev Donald L. Turcotte Andrea Donnellan Kristy F. Tiampo Jose Fernandez 《Pure and Applied Geophysics》2010,167(8-9):967-977
In weather forecasting, current and past observational data are routinely assimilated into numerical simulations to produce ensemble forecasts of future events in a process termed “model steering”. Here we describe a similar approach that is motivated by analyses of previous forecasts of the Working Group on California Earthquake Probabilities (WGCEP). Our approach is adapted to the problem of earthquake forecasting using topologically realistic numerical simulations for the strike-slip fault system in California. By systematically comparing simulation data to observed paleoseismic data, a series of spatial probability density functions (PDFs) can be computed that describe the probable locations of future large earthquakes. We develop this approach and show examples of PDFs associated with magnitude M > 6.5 and M > 7.0 earthquakes in California. 相似文献
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166.
José Luis Arce Rodolfo Macías Armando García Palomo Lucia Capra José Luis Macías Paul Layer Hernando Rueda 《Journal of Volcanology and Geothermal Research》2008
Zempoala is an extinct Pleistocene (∼ 0.7–0.8 Ma) stratovolcano that together with La Corona volcano (∼ 0.9 Ma) forms the southern end of the Sierra de las Cruces volcanic range, Central Mexico. The volcano consists of andesitic and dacitic lava flows and domes, as well as pyroclastic and epiclastic sequences, and has had a complex history with several flank collapses. One of these collapses occurred during the late Pleistocene on the S–SE flank of the volcano and produced the Zempoala debris avalanche deposit. This collapse could have been triggered by the reactivation of two normal fault systems (E–W and NE–SW), although magmatic activity cannot be absolutely excluded. The debris avalanche traveled 60 km to the south, covers an area of 600 km2 and has a total volume of 6 km3, with a calculated Heim coefficient (H/L) of 0.03. Based on the textural characteristics of the deposit we recognized three zones: proximal, axial, and lateral distal zone. The proximal zone consists of debris avalanche blocks that develop a hummocky topography; the axial zone corresponds with the main debris avalanche deposit made of large clasts set in a sandy matrix, which transformed to a debris flow in the lateral distal portion. The deposit is heterolithologic in composition, with dacitic and andesitic fragments from the old edifice that decrease in volume as bulking of exotic clasts from the substratum increase. Several cities (Cuernavaca, Jojutla de Juárez, Alpuyeca) with associated industrial, agricultural, and tourism activities have been built on the deposit, which pose in evidence the possible impact in case of a new event with such characteristics, since the area is still tectonically active. 相似文献
167.
Joan Fabres Tommaso Tesi Jose Velez Fabian Batista Cindy Lee Antoni Calafat Serge Heussner Albert Palanques Stefano Miserocchi 《Continental Shelf Research》2008
To investigate the role of coastal canyons in the transfer of organic matter from the shelf to the slope and basin, we deployed sediment trap/current meter pairs at the head of five canyons in the Gulf of Lions (GoL) between November 2003 and May 2004. Analysis of organic carbon, biogenic silica, Corg isotopic composition, Corg/total nitrogen, chloropigments, and amino acids clearly shows the seasonal influence and effect of extreme meteorological events on the composition of collected particles. The sampling period was divided into three “scenarios”. The first corresponded to a large easterly storm and flood of the Rhone river during stratified water column conditions; the composition of material collected during this event was influenced by increased transfer of riverine and coastal particulate matter, with a lower Corg content. During the second “fall-winter” scenario, northern and northwestern winds blowing over the shelf caused cooling and homogenization of the shelf water column; particles collected at this time reflected the homogeneous source of particulate matter transported through canyons; particles sitting in the vicinity of canyon heads are most likely swept downslope by the general south-westward circulation. Organic tracers indicate a degraded origin for organic matter transported during this period. A third “spring” scenario corresponded to northern winds alternating with eastward windstorms that triggered and/or enhanced the cascading of dense waters accumulated on the bottom of the shelf due to previous cooling. These conditions occurred in conjunction with increased phytoplankton productivity in shelf surface waters. Organic matter advected mainly by dense shelf water cascading was fresher due to the transport of newly produced particles and a variable terrestrial fraction; this fraction depended on the proportion of resuspended material accumulated during previous high discharge periods that was involved in each transport pulse. The tight link shown between meteorological conditions and organic matter transport is important for continental margin geochemical studies as future changes in climatic conditions may lead to dramatic changes in carbon sequestration capability and in the ecosystems of deep margin environments. 相似文献
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169.
Pere Blay Julia Suso Almudena Robert Jose Luis Requena Jorge Alamo Victor Reglero Chris J. Eyles 《Astrophysics and Space Science》2001,276(1):311-323
The LEGRI Science Operation Center (SOC) is the single contact pointbetween the MINISAT-01 Centro de Operaciones Científicas (COC)located at Villafranca del Castillo (Madrid) and the LEGRI Consortium.Its architecture, operational procedures and associated software hasbeen developed at the Universities of Valencia and Birmingham on thescope to define a integrated Data Analysis System, able to perform thedaily follow-up of the instrument health, raw data files decompressionand archiving activities (on-line and historical). Pointing and telecommandfiles generation is also a SOC responsibility.The aim of this paper is to report the SOC activities during the two yearsof LEGRI operations. Conclusions about the SOC architecture and proceduresevolution on how to handle the operations for space-borne instrumentation,are also presented.Special attention has been paid to the operative evaluation of the pointingreconstruction solutions from the MINISAT-01 Attitude Control System bycomparing them with those obtained with the LEGRI Star Sensor. The analysisof one year of observations shows the good agreement between both sets ofdata. No systematic deviations have been found with an averaged standarddeviation of 1 degree in alpha and delta coordinates. For most of the timethe MINISAT pointing system is working slightly better than expected andwithin specifications. 相似文献
170.