Transformations of biogenic substances in Tatar Strait water (the Sea of Japan): Analysis of mathematical modeling results

The state of the marine environment (the temperature, light intensity, transparency, biogenic load) in Tatar Strait was assessed based on mean annual data from literary sources and with the use of GIS “Sakhalin Shelf.” The entire strait was divided into three regions (northern, southwestern, and southeastern), and water exchange between them for each month was estimated by using Bergen Oceanic Model. The information about the state of the marine environment and water exchange characteristics was used as input data for a hydroecological model, which enabled the assessment of annual variations of biogenic substance concentrations and biomasses of microorganisms (heterotrophic bacteria, three groups of phytoplankton, and two groups of zooplankton) in the strait regions chosen. The development conditions of microorganism biomasses within the year can be characterized by their activity indices (specific growth rates), the values of internal fluxes of biogenic substances, and calculated bioproductivity values. The calculated biogenic substance concentrations and phytoplankton bioproductivity values showed good agreement with the estimates for the Sea of Japan and Tatar Strait available from the literature.     

Reconstruction of the annual variations of thermohaline characteristics and water circulation on the northeastern Sakhalin Shelf

Methods of statistical analysis and GIS Sakhalin Shelf have been used to reconstruct the annual variations of water temperature, salinity, and density from the surface to the bed at 60 standard oceanographic stations on northeastern Sakhalin shelf (with the total duration of observations of ～40 years). Numerical simulation using Bergen University oceanic model has been applied to calculate the spatial fields of water temperature and salinity at standard horizons in nodes of a regular grid. The analysis of calculation results revealed new features of the hydrological regime and gave previously unknown thermohaline fields with maximal detail for full annual cycle. The obtained data were used to evaluate the mean monthly three-dimensional water circulation.     

The calculation of meteor motion parameters based on the single station TV observations

Recently, television observations of meteors have steadily replaced photographic observations. Television recording with short exposures is a close analog of a photographic survey with a rotary shutter in the form of a system of set time marks on the meteor track. Each meteoric event is a series of recordings of separate phases of the motion of a meteor. This allows for the use of the geometric method for the determination of the motion parameters of meteors. In this work, a critique is given regarding the concept proposed by K.P. Stanyukovich in 1932–1939, and a mathematical justification of the geometric method of the analysis of the television images of meteors is given.     

Geological structure of central East Antarctica from geophysical data

Examination of the subglacial topography of central East Antarctica reveals the block structure of the Earth’s crust in this region. The intracontinental blocks of the subglacial Vostok Highlands (400 masl), Komsomol’sky Mountains (700 masl), Schmidt Basin (150 masl), and Aurora Basin (?300 masl) are distinguished. The geological nature of the Komsomol’sky Subglacial Mountains (KSM) and the Schmidt Subglacial Basin (SSB) is interpreted from gravity measurements and regional aerogeophysical routes. The basin of Vostok Subglacial Lake (VSL) is located in the conjugation zone of these blocks. The KSM are considered to be a block of the Proterozoic mobile belt disturbed by a system of normal and reverse faults. The SSB is a rigid cratonic block partly overlapped by platform cover. The localization of the VSL Graben in the zone of conjugation of heterogeneous blocks testifies to its formation in a deep fault zone characterized by intense normal and reverse dislocations.     

Pseudosecondary clastic rocks of the Dzuramtai massif (Southern Mongolia)

Specific rocks (tectonomixtites) developed in the framing of Mongolian granite massifs (Dzuramtai and some others) at the Mesozoic section bottom are studied. It is shown that the tectonomixtites are tectonic rocks rather than eluvial or sedimentary rocks, as was considered previously. They formed in the Cenozoic in the process of granite protrusion beneath a thick sedimentary cover owing to the crushing of granites and abrasion of granite fragments with the subsequent transformation of clastic rocks by groundwaters (suffosion). In this process, clastic rocks yielded fine products of the destruction of feldspars and quartz was concentrated. The rocks formed at relatively low temperatures (no more than 200–300°C) under stress strains.     

Crystalline Protrusion as the Typical Structural–Tectonic Model of Intragranite Hydrocarbon Accumulation

Geotectonics - The paper deals with issues related to the study questions on magmatic tectonics and intragranitic hydrocarbon accumulating formation: (i) post-magmatic structure of granitic massifs...     

Suspended and Dissolved Forms of Nutrients: Their Relationships and Interaction in the Major Tributaries of the Caspian Sea

Normal annual data are used to evaluate the within-year variations in the concentrations of biogenic substances (organic and mineral components of N and P, dissolved organic carbon, inorganic Si) in the major tributaries of the Caspian Sea. Variations in the concentrations of biogenic substances are analyzed, the relationships between their mass concentrations in individual months are evaluated, and correlation between the organic and mineral components of N and P and their aggregated fractions are established. The obtained high-significance correlation between the concentrations of N and P components suggests that the rates of biochemical processes of biogenic substance transformation taking place in the water of tributaries are commensurable.     

The Role of Microorganisms in the Transformation of Biogenic Substances in the Caspian Sea Ecosystem: An Assessment Based on Mathematical Modeling

A hydroecological model is used to study the transformations of biogenic-element (N, P, C, and Si) compounds in different parts of the Caspian Sea. The existing notions of the biotransformation processes of these compounds in the marine environment are formalized. The state of the marine environment is characterized based on calculated annual dynamics of biogenic element concentrations, their relationships, and internal fluxes. Relationships between the concentrations of N and P mineral components are used to establish distinctions between different parts of the sea in the conditions of primary production limited by biogenic elements, as well as the development conditions of aquatic lifeforms (nutrient consumption, release of metabolic products, and detritus formation).     

Analysis of Conditions of Petroleum Hydrocarbon Transformations in Seawater and Simulation of This Process in Aniva Bay

Simulation methods are used to study the self-purification capacity of water from Aniva Bay before the construction on the coast of the bay of the world's largest liquefied natural gas plant and oil loading terminals for ships with a displacement of 100 000 t or more. The calculations are made by using a hydro-ecological model and long-term data on Aniva Bay oceanography. Its water area was divided into five areas, and for these areas, we determined the hydrological and hydrochemical characteristics, evaluated fluxes through their boundaries, estimated petroleum hydrocarbon (PHC) loads, and calculated the annual dynamics of their concentrations and the biomasses of oil-oxidizing bacteria. PHC balances for the five water areas and Aniva Bay as a whole were calculated. PHC consumption by oil-oxidizing bacteria is the most important process of PHC transformation. The discrepancy of the estimated PHC balance in Aniva Bay was found to equal 2.61%, which is within the calculation accuracy.     

Formation and Evolution of the Anaerobic Zone in the Black Sea from the Most Recent Salinization to the Present State: Retrospective Estimation Based on Mathematical Modeling

It is established that the formation and evolution of the anaerobic zone of the Black Sea are associated with the beginning and development of the most recent salinization of the sea and the formation of pycnocline at intermediate depths; a deterioration of deep-water aeration and the formation of anaerobic conditions in deeper layers; the rate of sulfate-reduction first in the near-bed layer and later, as oxygen is depleted, in the water mass. Formalization of these processes based on refined present-day data on water balance enabled the reproduction of profiles of water salinity and vertical-exchange coefficient for different formation stages of salinity regime in the Black Sea. The vertical distribution of oxygen and hydrogen sulfide is reconstructed, and the rates of oxygen consumption in water column and sulfate reduction in the near-bed layer and at the upper boundary of the anaerobic zone are evaluated in numerical experiments. The obtained data show the transformation of the vertical distribution of oxygen and hydrogen sulfide in the Black Sea from the beginning of its most recent salinization to the present-day state. It is shown that the anaerobic zone rises from 2000 to 200 m within 500–600 years (in the period 3.9–4.5 Ka from the beginning of water exchange through the Bosphorus), and next the upper boundary of the anaerobic zone slowly ascends up to its present-day position (130–180 m). Mathematical modeling was used to evaluate the fluxes of oxygen and hydrogen sulfide at different formation stages of the anaerobic zone in the sea.__________Translated from Vodnye Resursy, Vol. 32, No. 3, 2005, pp. 307–321.Original Russian Text Copyright © 2005 by Leonov, Shaporenko.