Study of fluoride in polluted and unpolluted estuarine environments

Mindhola River estuary, which receives industrial waste containing high concentrations of fluoride, and Purna River estuary, which is free from fluoride contamination, have been investigated. While fluoride behaved conservatively in Purna River estuary, significant deviation from the theoretical dilution line (TDL) in the chlorinity range 0·5–8‰ was observed in Mindhola River estuary due to the externally added fluoride which largely remained in solution. The excess of fluroide over the theoretically calculated value was at a maximum around a chlorinity of 3‰. High natural fluoride content of the river waters resulted in F/Cl ratios exceeding 300 × 10⁻⁵ at low chlorinities. The ratio decreased rapidly with increasing chlorinity and the value near to that of seawater was observed at chlorinities above 14‰.     

Palaeo-carbonate seep structures above an oil reservoir, Gryphon Field, Tertiary, North Sea

Petrographic and geochemical analyses performed on a North Sea core from the Gryphon Field reveal the presence of palaeo-degassing features surrounded by injected sandstones in the Eocene interval. The injected sandstones are oil-stained and poorly cemented by carbonate and quartz. ¹⁸O isotope analyses indicate that carbonate cementation occurred during shallow burial (likely less than about 300 m). Depleted ¹³C (around –30 V-PDB) carbonate cement suggests that bicarbonate was derived from the microbial oxidation of oil and gas. Late quartz overgrowths enclose oil present in the injected units. The tubular degassing conduits are composed of zoned cements and have ¹⁸O and ¹³C isotope values similar to the injected sandstones, indicating that oil and gas seepage induced the precipitation of authigenic carbonate in the shallow subsurface. Oil inclusions in inter- and intra-crystal cement sites in both injected sandstones and degassing conduits indicate that oil seepage was an ongoing feature at shallow burial. A proposed model involves oil and gas seepage and the formation of the degassing conduits, followed by a sand injection phase. It seems likely that oil and gas continued to leak towards the seabed by exploiting the network of permeable injected sandstones and the horizons of porous degassing features.     

A review of eastern tropical Pacific oceanography: Summary

The collection of articles in this volume reviewing eastern tropical Pacific oceanography is briefly summarized, and updated references are given. The region is an unusual biological environment as a consequence of physical characteristics and patterns of forcing – including a strong and shallow thermocline, the ITCZ and coastal wind jets, equatorial upwelling, the Costa Rica Dome, eastern boundary and equatorial current systems, low iron input, inadequate ventilation of subthermocline waters, and dominance of ENSO-scale temporal variability. Remaining unanswered questions are presented.     

Aleksandr Georgievich Rozanov (on his 70th birthday)

Chronicle

Aleksandr Georgievich Rozanov (on his 70th birthday)     

Temperature fluctuations in the atmospheric surface layer over the thermally inhomogeneous underlying surface

The influence of both spatial and temporal temperature inhomogeneities of the underlying surface on the temperature field in an unstably stratified atmospheric surface layer is considered. The methods of correlation and spectral analyses are proposed to estimate statistical characteristics of surface-air temperature fluctuations caused by both turbulent mixing and inhomogeneities in the temperature of the underlying surface. Analysis of experimental data obtained from measurements in the atmospheric surface layer yields estimates for the contribution made by the time-dependent thermal properties of the underlying surface to the total variance of air-temperature fluctuations. It is shown that the additional air-temperature fluctuations generated by surface-temperature inhomogeneities and unrelated to shear flow may reach 70% and 30% of the total variance of measured fluctuations under variable cloudiness and clear skies, respectively. For the height z = 2 m within the wave-number range 2 × 10^?3 rad m^?1 < k < 0.1 rad m^?1, the contribution made by a spatial surface-temperature inhomogeneity to the variance of air-temperature fluctuations does not exceed 10% of the total variance. Correlation and spectral analyses of experimental data make it possible to isolate the spectra of properly turbulent fluctuations from the measured fluctuations and thus to obtain more accurate values of the universal function of similarity theory for temperature in the range of small wave numbers beyond the inertial range.     

Combined numerical model of currents, waves, and sediment transport in Lake Donuzlav

We present a numerical model of the dynamics of Lake Donuzlav, which enables one to perform simultaneous numerical analyses of the currents, sea level, waves, and sediment transport. The model is based on the hydrodynamic block and the spectral wave model. For typical storm situations, we study the specific features of the integral circulation of waters and the three-dimensional structure of currents, investigate the wind-induced wave fields, and evaluate the flows of sediments and deformations of the bottom. The presence of intense eddy structures is revealed in the field of currents caused by the bottom topography. A significant intensification of waves in the south part of the lake is established in the case of penetration of storm waves through the strait. It is shown that the account of waves leads to qualitative changes in the structure of circulation in the lake and to the formation of well-pronounced areas of wave-induced elevations and lowerings of the sea level. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 43–65, March–April, 2006.     

Bottom foraminiferal assemblages in the Deryugin Basin (Sea of Okhotsk) during the past 26000 years

Benthic foraminifers from a core of bottom sediments obtained in the Deryugin Basin at a depth of 1750 m were examined. Three distinct benthic foraminiferal assemblages that replaced one another throughout the last 26000 years were recognized. The assemblage dominated by Alabaminella weddellensis, Uvigerina auberiana, and Cassidulina translucens dwelled here from 26 to 24 ky B.P. The sediments of the glacial period between 26 and 12.18 ky B.P. contain no benthic foraminifers. The composition of the sediments suggests the existence of active bottom vents of gas-bearing fluids during that time. The dominance of Brizalina spissa, Uvigerina peregrina, and Cassidulina laevigata is characteristic of the period from 12.18 to 7 ky B.P., when the productivity of the surface waters in the region was high, and warm, poorly oxygenated waters spread over the bottom of the basin. During the past 7 000 years, the bottom conditions in the sea were similar to the present-day conditions and an assemblage with the dominance of Gyroidina orbicularis, Uvigerina auberiana, and Cassidulina teretis developed in the region.     

Viscous model of plate tectonics for the Black Sea region (in relation to the problem of the late Cenozoic evolution of the Black Sea basins)

A numerical model of the Black Sea region (Northeastern Mediterranean) is presented in which it is regarded as a part of the mosaic plate ensemble consisting of the fixed East European platform; the active Arabian, Adriatic, and Pannonian plates; and passive East and West Black Sea and Mysian microplates, which are embedded in a plastically deformable regional orogenic matrix. The fields of displacements, stresses, and deformations in the region are calculated by means of the finite element method within the framework of a linear-viscous rheology approach to a system with nonhomogeneous viscosities. The velocity field obtained is in good agreement with published data of direct observations of plate displacements in the region. In the pressure field, areas of low pressure and decompression are established in the western part of Black Sea and in the south of the Mysian microplate. The poles of rotation of the East and West Black Sea microplates and of the Mysian microplate are computed. For the latter two microplates, significant rotational components are suggested. The East Black Sea microplate acts mostly as indenter, which transmits the collisional motion from the Arabian plate to the southern edge of the East European platform including the Crimea. According to the geodynamical model, the rates of the Cenozoic sedimentation in the Black Sea depression at the collision stage (Oligocene-Pliocene) result from the greater compression of the East Black Sea microplate as compared to the West Black Sea microplate, which, probably, experienced a kind of extension.     

Weakly non-linear free oscillations in a basin of variable depth

Weakly non-linear free oscillations in a basin of variable depth filled with non-viscous fluid are investigated in terms of the long waves theory using the perturbation technique. Solutions to the initial two approximations for the horizontal velocity component and free surface departure are numerically derived. An attempt is made to determine the area of applicability of the linear theory by applying a parabolic bottom profile to the basin.Translated by V. Puchkin.