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441.
Pore water aliquots were taken with an in situ close interval sampler: the “Peeper”.We report here the pore water concentration profiles of TCO2, SO4, TH2S, Ca and the trace metals Mn, Cu, Pb, Cd and Cr from sediments of a relatively polluted area, the Villefranche Bay, on the French Riviera (close to Nice).We investigated the major ion concentrations in order to establish geochemical mass balances of organic matter oxidation. ΔTCO2/ΔSO4 was <−2.0, reflecting the precipitation of calcite as confirmed by the calcium profile. Reduction of sulfate led to increasing sulfide concentrations with depth.Trace metal interstitial water concentrations decreased from 63 to 5 nM, 18 to 4 nM and 6.6 to less than 2 nM for Cu, Pb and Cr, respectively. Cd showed a different pattern with top and deep values of 0.7 nM and a minimum of 0.27 nM.Thermodynamic calculations were performed which suggest the potential formation of mineral phases such as sulfides. 相似文献
442.
Santos MM ten Hallers-Tjabbes CC Vieira N Boon JP Porte C 《Marine environmental research》2002,54(3-5):661-665
Normal and imposex-affected female Buccinum undatum were sampled from the open North Sea at three locations, one with low, and two with high shipping densities. Cytochrome P450 components and P450 aromatase activity were determined in the microsomal fractions isolated from pooled digestive gland/gonads. Cytochrome P450 aromatase activity was significantly higher (P < 0.05) in normal females collected in the low shipping density area (1,325 +/- 295 fmol/h/mg protein) than levels from imposex animals from a high shipping density area (620 +/- 287 fmol/h/mg protein). A negative correlation was found between aromatase activity and organotin body burden (r = -0.99). Levels of CYP450, cytochrome b5 and NADPH cytochrome c reductase activity did not show differences among groups. This is the first field evidence of depressed aromatase activity in imposex affected females, although additional research under laboratory controlled conditions is required to fully understand the mechanisms underlying the development of imposex in this species. 相似文献
443.
This paper deals with the solution of the problem of the dynamic response of the leg of a tension leg platform subjected to an axial, suddenly applied load at one end, considering a highly simplified model but taking into account several complicating factors. The problem is solved by means of a non-harmonic Fourier expansion in terms of eigenfunctions obtained from a non-regular Sturm-Liouville system. 相似文献
444.
Distributions of physical, chemical and biological characteristics were recorded for coastal waters off south-west Ireland during the summers of 1985–1987. A number of thermal fronts were identified from both shipboard measurements and satellite imagery. Upwelling was shown to be an important process in the area and enhanced phytoplankton biomass and productivity were associated with areas of upwelling and the fronts. Phytoplankton species composition, although varying between cruises, was associated with differences in hydrographic features. 相似文献
445.
Donald J. Walter Douglas N. Lambert David C. Young Kevin P. Stephens 《Geo-Marine Letters》1997,17(4):260-267
Real-time trackline plots of surficial sediment acoustic impedance delineate several sedimentary facies off Garden Key in
the Dry Tortugas. The sea floor within a 6×6 km surveyed area consists of carbonate muds (silts), sands and shell, rock, and
live corals. The 4-kHz acoustic data supports this finding by providing a pictographic representation of the distribution
and structure of several sediment facies types. Plotting the gridded acoustic data with commercial mapping software (Surfer)
provides a three-dimensional (3D) perspective of the bottom topography with a color contour map of surficial sediment impedance
(upper 0.4 m) draped over the 3D surface. 相似文献
446.
The expansion of the temperature anomaly field in the North Atlantic is considered using natural orthogonal functions of depth. It is shown that the first few components of this expansion describe the field both at the surface and in the upper 1000 m layer accurately enough. The relation between the water temperature anomaly at some levels and the above components is estimated for various regions of the ocean.Translated by Mikhail M. Trufanov. 相似文献
447.
P. Ziveri R.C. Thunell D. Rio 《Deep Sea Research Part I: Oceanographic Research Papers》1995,42(11-12)
Seasonal changes in coccolithophore cell densities in the San Pedro Basin, Southern California Bight, were investigated for the period October 1991 to September 1992. Coccolitho phore cell densities ranged from 6.3 × 104 coccospheres per liter in March 1992 to 0 cells per liter in November 1991. High coccolithophore concentrations occurred in late winter and spring, and low densities occurred in the summer and fall. The high coccolithophore densities during spring 1992 were associated with unusually low surface nutrient concentrations and a lack of upwelling, suggesting that the high densities were not part of a typical spring phytoplankton bloom in this region. We propose that the suppression of upwelling during spring 1992 may have been related to the prevailing ENSO conditions. Emiliania huxleyi type A dominated the total coccolithophore population throughout the year, Umbilicosphaera sibogae var. sibogae being the second most important contributor to the coccolithophore assemblages. 相似文献
448.
Sediment-starved sand ridges on a mixed carbonate/siliciclastic inner shelf off west-central Florida
S. E. Harrison S. D. Locker A. C. Hine J. H. Edwards D. F. Naar D. C. Twichell D. J. Mallinson 《Marine Geology》2003,200(1-4):171-194
High-resolution side-scan mosaics, sediment analyses, and physical process data have revealed that the mixed carbonate/siliciclastic, inner shelf of west-central Florida supports a highly complex field of active sand ridges mantled by a hierarchy of bedforms. The sand ridges, mostly oriented obliquely to the shoreline trend, extend from 2 km to over 25 km offshore. They show many similarities to their well-known counterparts situated along the US Atlantic margin in that both increase in relief with increasing water depth, both are oriented obliquely to the coast, and both respond to modern shelf dynamics. There are significant differences in that the sand ridges on the west-central Florida shelf are smaller in all dimensions, have a relatively high carbonate content, and are separated by exposed rock surfaces. They are also shoreface-detached and are sediment-starved, thus stunting their development. Morphological details are highly distinctive and apparent in side-scan imagery due to the high acoustic contrast. The seafloor is active and not a relict system as indicated by: (1) relatively young AMS 14C dates (<1600 yr BP) from forams in the shallow subsurface (1.6 meters below seafloor), (2) apparent shifts in sharply distinctive grayscale boundaries seen in time-series side-scan mosaics, (3) maintenance of these sharp acoustic boundaries and development of small bedforms in an area of constant and extensive bioturbation, (4) sediment textural asymmetry indicative of selective transport across bedform topography, (5) morphological asymmetry of sand ridges and 2D dunes, and (6) current-meter data indicating that the critical threshold velocity for sediment transport is frequently exceeded. Although larger sand ridges are found along other portions of the west-central Florida inner shelf, these smaller sand ridges are best developed seaward of a major coastal headland, suggesting some genetic relationship. The headland may focus and accelerate the N–S reversing currents. An elevated rock terrace extending from the headland supports these ridges in a shallower water environment than the surrounding shelf, allowing them to be more easily influenced by currents and surface gravity waves. Tidal currents, storm-generated flows, and seasonally developed flows are shore-parallel and oriented obliquely to the NW–SE trending ridges, indicating that they have developed as described by the Huthnance model. Although inner shelf sand ridges have been extensively examined elsewhere, this study is the first to describe them in a low-energy, sediment-starved, dominantly mixed siliciclastic/carbonate sedimentary environment situated on a former limestone platform. 相似文献
449.
An extensive experimental and computational investigation of the combined and separate effects of free surface and body on the lift characteristics of a pair of fins attached to a strut and fin alone is conducted. The results reveal that the free-surface effect becomes significant when the depth of submergence to chord ratio (H/c) is less than three. The effect of the strut is also realized for shallower depth of submergence of the fins through free-surface deformation leading to a significant change in the incidence angle of the flow to the fins. The numerical results based on the Higher Order Boundary Element Method with the linearized free-surface condition show good agreement with the experimental results for fin (foil) alone even at shallow submergence, but some discrepancies appear for the fin attached to the strut at higher speeds mostly due to the neglect of the nonlinear free-surface effect. 相似文献
450.
We perform the analysis of the time spectra of four tsunamis generated in the Black Sea by the earthquakes of 26.07.1927,
11.09.1927, 26.12.1939, and 12.07.1966. For the analysis of the spectra, we used digitized marigrams obtained for 12 points
of the Black-Sea coast. The obtained spectra are, as a rule, multimode and have 1–4 spectral maxima. One maximum corresponds
to the periods typical of tsunami waves and the other maxima correspond to the oscillations of the sea level with lower frequencies.
It seems likely that the events of tsunami are accompanied by low-frequency oscillations of the level caused by the atmospheric
forcing, seiches, or other factors. In numerous cases, the oscillations from the predominant energy range lie outside the
characteristic range of periods of the tsunami waves.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 21–30, September–October, 2007. 相似文献