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排序方式: 共有122条查询结果,搜索用时 15 毫秒
21.
Olga Sarychikhina Ewa Glowacka Braulio Robles F. Alejandro Nava Miguel Guzmán 《Pure and Applied Geophysics》2015,172(11):3139-3162
22.
23.
Richard H. Bennett William R. Bryant Wayne A. Dunlap George H. Keller 《Marine Georesources & Geotechnology》2013,31(4):327-335
Abstract This report describes the instrumentation, initial results, and progress of an experiment designed to measure and monitor submarine sediment pore water and hydrostatic pressures in a selected area of the Mississippi Delta. The experiment also is intended to monitor significant pressure perturbations during active storm periods. Initial analysis of the data revealed excess pore water pressures in the silty clay sediment at selected depths below the mudline. Continuous monitoring of the pore water and hydrostatic pressures was expected to reveal important information regarding sediment pore water pressure variations as a function of the geological processes active in the Mississippi Delta. 相似文献
24.
ZHANG Dan ZHANG Yu MORAWSKA Ewa BIELAWSKI Leszek KRASINSKA Grazyna DREWNOWSKA Ma gorzata PANKAVEC Sviatlana SZYMANSKA Karolina FALANDYSZ Jerzy 《山地科学学报》2013,10(4):621-627
In the current study, we determined concentrations and transfer rates of Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, P, Rb, Sr and Zn to Brown Birch Scaber Stalks (Leccinum scabrum) mushrooms emerged in the area of Sudety Mountains (Sudetes) in Poland. Fruiting bodies and topsoil samples beneath L. scabrum were collected form the K odzka Dale. The trace elements were determined using validated method and inductively coupled plasma - atomic emission spectroscopy (ICP-AES) for final measurement. Mushrooms contained Ag, Cr, Hg, Co, Ni and Sr at < 1.0 μg/g dry weight; Ba and Pb at ~1.0 μg/g dw; Cd at < 5 μg/g dw; Cu and Mn at > 10 μg/g dw; Al and Ca at ~100 μg/g dw; Fe, Na, Rb and Zn at 100 to 500 μg/g dw, Mg at ~1,000 μg/g dw; P at ~5,000 μg/g dw and K at ~30,000 μg/g dw. Ca, Mn and Ni were nearly equally distributed between stipes and caps; stipes compared to caps were enriched in Ba, Na and Sr, while caps were enriched in Ag, Al, Cd, Co, Cr, Cu, Fe, K, P, Pb, Rb and Zn. The values of bioconcentration factor (BCF) varied highly depending on chemical element and were >1 for Ag, Cd, Cu, K, Mg, Na, P, Rb and Zn, while <1 for Al, Ba, Ca, Co, Cr, Fe, Mn, Ni, Pb and Sr. Topsoil showed elevated content of lead and mean concentration was 99 ± 32 μg/g dw, while cadmium was at 0.41 ± 0.15 and those two highly toxic to human elements occurred in edible caps of L. scabrum at 4.5 ± 2.2 and 2.9 ± 2.0 μg/g dw, respectively. 相似文献
25.
Dynamics of the circulation in the Sea of Marmara: numerical modeling experiments and observations from the Turkish straits system experiment 总被引:4,自引:3,他引:1
Jacopo?ChiggiatoEmail author Ewa?Jarosz Jeffrey?W.?Book James?Dykes Lucio?Torrisi Pierre-Marie?Poulain Riccardo?Gerin Jochen?Horstmann ?ükrü?Be?iktepe 《Ocean Dynamics》2012,62(1):139-159
During September 2008 and February 2009, the NR/V Alliance extensively sampled the waters of the Sea of Marmara within the
framework of the Turkish Straits System (TSS) experiment coordinated by the NATO Undersea Research Centre. The observational
effort provided an opportunity to set up realistic numerical experiments for modeling the observed variability of the Marmara
Sea upper layer circulation at mesoscale resolution over the entire basin during the trial period, complementing relevant
features and forcing factors revealed by numerical model results with information acquired from in situ and remote sensing
datasets. Numerical model solutions from realistic runs using the Regional Ocean Modeling System (ROMS) produce a general
circulation in the Sea of Marmara that is consistent with previous knowledge of the circulation drawn from past hydrographic
measurements, with a westward meandering current associated with a recurrent large anticyclone. Additional idealized numerical
experiments illuminate the role various dynamics play in determining the Sea of Marmara circulation and pycnocline structure.
Both the wind curl and the strait flows are found to strongly influence the strength and location of the main mesoscale features.
Large displacements of the pycnocline depth were observed during the sea trials. These displacements can be interpreted as
storm-driven upwelling/downwelling dynamics associated with northeasterly winds; however, lateral advection associated with
flow from the Straits also played a role in some displacements. 相似文献
26.
Oscar?LaurentEmail author Armin?Zeh Axel?Gerdes Arnaud?Villaros Katarzyna?Gros Ewa?S?aby 《Contributions to Mineralogy and Petrology》2017,172(9):80
In plutonic systems, magma mixing is often modelled by mass balance based on whole-rock geochemistry. However, magma mixing is a chaotic process and chemical equilibration is controlled by non-linear diffusive–advective processes unresolved by the study of bulk samples. Here we present textural observations, LA-(MC-)ICP-MS trace element and Sr–Nd isotopic data of accessory apatites and titanites from a hybrid granodiorite of the Neoarchean Matok pluton (South Africa), collected in a zone of conspicuous mixing between mafic and felsic magmas. Apatite grains mostly show a pronounced zoning in CL images, corresponding to abrupt changes in REE and HFSE concentrations recording their transfer through compositionally different melt domains during mixing. These grains crystallized early, at temperatures of 950–1000 °C. Titanite grains crystallized at temperatures of 820–900 °C (Zr-in-sphene thermometry). They show limited intra-grain chemical variations but huge inter-grain compositional scatter in REE and HFSE, pinpointing crystallization within a crystal mush, from isolated melt pockets having different composition from one another owing to incomplete chemical homogenization and variable Rayleigh fractionation. These chemical–textural characteristics, in combination with partitioning models and Polytopic Vector Analysis, point to “self-mixing” between co-genetic dioritic and granodioritic/granitic magmas. Both resulted from differentiation of mantle-derived mafic melts, showing that mixing does not necessarily involve magmas from contrasted (crust vs. mantle) sources. Systematic variations in εNd t (?4.5 to ?2.5) and 87Sr/86Sr(i) (0.703–0.707) of titanite and apatite grains/domains crystallized from the two magmas point to an isotopically inhomogeneous mantle source, which is not resolved by bulk-rock isotopic data. Interaction between the two magmas must have occurred at relatively high temperatures (ca. 900°C) so that their viscosity contrast remained low, allowing efficient mechanical mixing. Despite this, chemical homogenization was incomplete, as recorded by diffusive fractionation between REE–HFSE and Sr. Modelling thereof reveals that chemical exchange between the liquid phases of the two mixed magmas did not last more than a few tens to hundreds of years. The chemical equilibration between mixed magmas thus strongly depends on the considered elements and observational length scales. 相似文献
27.
Sea surface temperature (SST) from a near real-time data set produced from satellites data has been assimilated into a coupled
ice–ocean forecasting model (Canadian East Coast Ocean Model) using an efficient data assimilation method. The method is based
on an optimal interpolation scheme by which SST is melded into the model through the adjustment of surface heat flux. The
magnitude and space–time variation of the adjustment depend on the depth of heat diffusion into the water column in response
to changes in surface flux, the correlation time scale of the data, and model and data errors. The diffusion depth is scaled
by the eddy diffusivity for temperature. The ratio of the model and data errors is treated as an adjustable parameter. To
evaluate the quality of the assimilation, the results from the model with and without assimilation are compared to independent
ship data from the Atlantic Zone Monitoring Program and the World Ocean Circulation Experiment. It is shown that the assimilation
has a significant impact on the modeled SST, reducing the root mean square difference (RMSD) between the model SST and the
ship SST by 0.63°C or 37%. The RMSD of the assimilated SST is smaller than that of the satellite SST by 0.23°C. This suggests
that model simulations or predictions with data assimilation can provide the best estimate of the true SST. A sensitivity
study is performed to examine the change of the model RMSD with the adjustable parameter in the assimilation equation. The
results show that there is an optimal value of the parameter and the model SST is not very sensitive to the parameter. 相似文献
28.
Comparison of Two Nonstationary Flood Frequency Analysis Methods within the Context of the Variable Regime in the Representative Polish Rivers 总被引:2,自引:0,他引:2
Witold G. Strupczewski Krzysztof Kochanek Ewa Bogdanowicz Iwona Markiewicz Wojciech Feluch 《Acta Geophysica》2016,64(1):206-236
Changes in river flow regime resulted in a surge in the number of methods of non-stationary flood frequency analysis. Common assumption is the time-invariant distribution function with time-dependent location and scale parameters while the shape parameters are time-invariant. Here, instead of location and scale parameters of the distribution, the mean and standard deviation are used. We analyse the accuracy of the two methods in respect to estimation of time-dependent first two moments, time-invariant skewness and time-dependent upper quantiles. The method of maximum likelihood (ML) with time covariate is confronted with the Two Stage (TS) one (combining Weighted Least Squares and L-moments techniques). Comparison is made by Monte Carlo simulations. Assuming parent distribution which ensures the asymptotic superiority of ML method, the Generalized Extreme Value distribution with various values of linearly changing in time first two moments, constant skewness, and various time-series lengths are considered. Analysis of results indicates the superiority of TS methods in all analyzed aspects. Moreover, the estimates from TS method are more resistant to probability distribution choice, as demonstrated by Polish rivers’ case studies. 相似文献
29.
A temperature‐time history for the granulite‐hosted Challenger gold deposit in the Christie Domain of the Gawler Craton, South Australia, has been derived using a range of isotopic decay systems including U–Pb, Sm–Nd, Rb–Sr and 40Ar/39Ar. Nd model ages and detrital zircon ages suggest a protolith age of ca 2900 Ma for the Challenger Gneiss. Gold mineralisation was probably introduced under greenschist/amphibolite‐facies conditions towards the end of the Archaean, between 2800 and 2550 Ma. However, evidence for the exact age and P‐T conditions of this event was almost completely removed by granulite‐facies metamorphism during the Sleafordian Orogeny, which peaked around ca 2447 Ma. Cooling to 350°C occurred before 2060 Ma. It is possible that the Christie Domain was then subject to further sedimentation and volcanism in the period ca 2000–1800 Ma before reburial and a second period of orogeny around ca 1710–1615 Ma. During this second orogeny, the eastern Christie Domain experienced heterogeneous fluid‐induced retrograde metamorphism at lower greenschist‐ to amphibolite‐facies conditions, with metamorphic grade varying between structural blocks. At this time, the Challenger deposit was subject to greenschist‐facies conditions (not significantly hotter than 350°C), while at Mt Christie (50 km to the south) lower amphibolite‐facies conditions prevailed and to the west the Ifould Block experienced extensive plutonism. A third very low‐temperature thermal pulse around ca 1531 Ma, which reached ~ 150–200°C, is recorded at the Challenger deposit. It is likely that the global Grenvillian Orogeny (1300–1000 Ma) was a major period of domain exhumation and juxtaposition. 相似文献
30.
Ewa Szalinska Janusz Dominik Davide A.L. Vignati Andrzej Bobrowski Boguslaw Bas 《Applied Geochemistry》2010
Water, suspended matter and sediment samples from a system heavily impacted by wastewater from numerous small tanneries (the upper Dunajec River, southern Poland) were collected to establish the annual cycle of Cr. To study possible oxidation processes the speciation of Cr and Mn concentrations were also investigated. This study showed that Cr(III and VI) temporal and spatial distributions are regulated by coupled anthropogenic (source location and emissions) and hydrologic factors (water flow and particle transport). Chromium(III) concentrations in all compartments varied seasonally as a function of the hydrological regime, production cycle in tanneries and distance from the discharge location. Cr(III) was largely associated with the particulate phase and rapidly deposited in river bed sediments. Contaminated river sediments were however flushed during flood periods to the reservoir located downstream from tanneries. During the tanning season (November to March), Chromium(III) concentrations in the water column and total Cr concentration in sediments exceeded relevant ecotoxicological guidelines only upstream from the reservoir, which trapped about 70% of the annual Cr(III) load transported by the Dunajec river. A correlation between Cr(VI)/Cr(III) ratios and Mn concentration in sediments downstream from the reservoir suggests the possibility of Cr(III) oxidation in natural conditions. 相似文献