Hydrocarbons in the modern sediments of the Caspian Sea

The presented results have been obtained in a study of the concentrations and composition of aliphatic and polycyclic hydrocarbons in bottom sediments of Volga delta branches and in its shallow zone (2009–2010), as well as the Caspian Sea proper (2010–2013). Oil hydrocarbon pollution has been found to manifest itself mostly in Volga delta branches, which, despite the low concentrations (up to 54.5 μg/g), showed higher hydrocarbons share in C_org (up to 33.8%), while the composition of alkanes suggested their oil genesis. The geochemical barrier the Volga–the Caspian Sea prevents anthropogenic hydrocarbons from entering the open parts of the Caspian. Bottom sediments in the shallow zone of the Northern Caspian, represented by coarse-grained material, are now polluted by oil hydrocarbons to a lesser extent compared with other areas. The highest concentrations of aliphatic hydrocarbons (up to 178 μg/g) were recorded in the deepsea bottom sediments of Derbent Depression and in depressions of the Middle and Southern Caspian. These areas show a higher concentration of C_org (up to 9.884%) and a low concentration of hydrocarbons in C_org (up to 0.16%), while odd high-molecular homologues (n-C₂₅–C₃₁) dominate in the composition of alkanes.     

Doubly Stochastic Earthquake Source Model: “Omega-Square” Spectrum and Low High-Frequency Directivity Revealed by Numerical Experiments

Since its formulation in 1967–1970, the classical ω ^?2 model of earthquake source spectrum awaits a consistent theoretical foundation. To obtain one, stochastic elements are incorporated both into the final structure of the fault and into the mode of rupture propagation. The main components of the proposed “doubly stochastic” model are: (1) the Andrews’s concept, that local stress drop over a fault is a random self-similar field; (2) the concept of rupture with running slip pulse, after Heaton; (3) the hypothesis that a rupture front is a tortuous, multiply connected (“lacy”) fractal polyline that occupies a strip of finite width close to the slip-pulse width; and (4) the assumption that the propagation distance of fault-guided, mostly Rayleigh waves from a failing spot on a fault is determined by the slip-pulse width. Waveforms produced by this model are determined based on the fault asperity failure model after Das and Kostrov. Properties of the model are studied by numerical experiments. At high frequency, simulated source spectra behave as ω ^?2, and acceleration spectra are flat. Their level, at a given seismic moment and rms stress drop, is inversely related to the relative width of the slip pulse. When this width is relatively low, a well-defined second corner frequency (lower cutoff of acceleration spectrum) is seen. The model shows clear dependence of propagation-related directivity on frequency. Between the first and the second corner frequency, amplitude spectra are strongly enhanced for the forward direction; whereas, above the second corner frequency, directivity is significantly reduced. Still, it is not inhibited totally, suggesting incomplete incoherence of the simulated radiator at high frequencies.     

Development of means and methods of drifter technology applied to the problem of the Black Sea research

During the last ten years, autonomous drifting platforms for data collection (drifters) equipped with Argos satellite communication devices have become one of the main components for the observation system in the upper layer of the ocean and surface atmosphere. This article presents the results of the Black Sea drifter monitoring in 2002–2006 within a number of international programs and projects. During this period, about 70 drifters manufactured by NPF Marlin-Yug Ltd. (Sevastopol, Ukraine) were deployed in the western part of the Black Sea. The drifters were mainly standard barometric Lagrangian tracers and a part of them were principally new temperature profiling buoys. Unique long-term data were obtained about the circulation of the surface currents and the dynamics of the temperature stratification within the seasonal thermocline and the cold intermediate layer.     

Modes of climate variability as simulated by a coupled general circulation model. Part I: ENSO-like climate variability and its low-frequency modulation

The El Niño-Southern Oscillation (ENSO) is investigated in a multicentury integration conducted with the coupled general circulation model (CGCM) ECHAM3/LSG. The quasiperiodic interannual oscillations of the simulated equatorial Pacific climate system are due to subsurface temperature anomaly propagation and a positive atmosphere-ocean feedback. The gravest internal wave modes contribute to the generation of these anomalies. The simulated ENSO has a characteristic period of 5–8 years. Due to the coarse resolution of the ocean model the ENSO amplitude is underestimated by a factor of three as compared to observations. The model ENSO is associated with the typical atmospheric teleconnection patterns. Using wavelet statistics two characteristic interdecadal modulations of the ENSO variance are identified. The origins of a 22 and 35?y ENSO modulation as well as the characteristic ENSO response to greenhouse warming simulated by our model are discussed.     

Defining dynamic pelagic habitats in oceanic waters off eastern Australia

Although many species in the pelagic ocean are widespread, they are not randomly distributed. These species may have associations with particular water masses or habitats, but to best understand patterns in the ocean, these habitats must be identified. Previous efforts have produced static or seasonal climatologies, which still represent smearing over habitats. The Eastern Tuna and Billfish Longline Fishery (ETBF) targets a range of high trophic level species in oceanic waters off eastern Australia. In this study, dynamic ocean habitats in the region were identified for each month based on cluster analysis of five oceanographic variables averaged at a monthly time scale and a spatial scale of 0.5° for the period 1995-2006. A total of seven persistent habitats were identified off eastern Australia with intra and interannual variation in size and location, indicating the importance of spatial and temporal variation in the dynamics of the region. The degree to which these dynamic habitats were distinguished was tested using (i) stable isotope analysis of top fish predators caught in the region and (ii) estimates of variation in estimated abundance generated from catch data from the fishery. More precise estimates (measured as lower total CV) of isotopic values from swordfish (Xiphias gladius), yellowfin tuna (Thunnus albacares) and albacore (Thunnus alalunga) were obtained for 4 of 6 isotope comparisons using the dynamic habitat groupings, which indicate that stratifying by pelagic habitat improved precision. Dynamic habitats produced more precise abundance estimates for 7 of 8 large pelagic species examined, with an average reduction in total CV of 19% compared to when abundance was estimated based on static habitat stratification. These findings could be used to guide development of effective monitoring strategies that can distinguish patterns due to environmental variation, and in the longer term, climate change.     

The use of 18O/16O ratios to study the formation and chemical origin of coal

The ${}^{18}\text{O}{}^{16}\text{O}$ ratios of some New Zealand peat, lignite and coal samples were measured and compared with those of various coal precursors (cellulose, lignin and plant resins). The results showed that the major source of oxygen in all cases (except that of high rank coal) was from cellulose with the contribution from lignin and plant resins being insignificant.     

On the determination of the diffusion coefficient of heterogeneous aerosols by the dynamic method

Summary It is shown that the marked influence of the air-flow on the value of the diffusion coefficient as determined by the dynamic method can be fully explained when heterogeneity of the condensation nuclei in the aerosol is assumed. A theory of the dynamic method for heterogeneous aerosols is given on the assumption that the diffusion loss of a mixture of condensation nuclei of different diffusion coefficients is the sum of the diffusion losse of its components. Procedures for resolving heterogeneous aerosols into their components using the dynamic method are developed. The accuracy attainable by one of the methods which requires no assumptions on the number of components in the aerosol under investigation is illustrated by a numerical example.

---

Zusammenfassung Es wird gezeigt, dass der bemerkenswerte Einfluss der Luftstromgeschwindigkeit auf die Grösse des mit der dynamischen Methode bestimmten Diffusionskoeffizienten völlig erklärt werden kann, wenn Heterogenität der Kondensationskerne im Aerosol angenommen wird. Eine Theorie der dynamischen Methode für heterogene Aerosole wird unter der Annahme, dass der Diffusionsverlust eines Gemisches von Kondensationskernen mit verschiedenen Diffusionskoeffizienten gleich der Summe der Diffusionsverluste ihrer Komponenten ist, gegeben. Verfahren der Zerlegung heterogener Aerosole in ihre Komponenten mittels der dynamischen Methode werden entwickelt. Die mit einem der Verfahren, welches keine Annahme über die Zahl der in dem zu untersuchenden Aerosol vorhandenen Komponenten benötigt, erreichbare Genauigkeit wird an einem numerischen Beispiel illustriert.

     

The Strel’tsovka uranium district: Isotopic geochronological (U-Pb,Rb-Sr,Sm-Nd) characterization of granitoids and their place in the formation history of uranium deposits

An isotopic geochronological study of Russia’s largest Strel’tsovka uranium district has been carried out. Polychronous granite generation, which determined the structure of the pre-Mesozoic basement, had important implications for the formation of volcanotectonic structural elements bearing economic uranium mineralization. The study of U-Pb, Rb-Sr, and Sm-Nd isotopic systems of whole-rock samples and minerals of granitic rocks allowed us to estimate the deportment of these systems in spatially conjugated granite-forming and hydrothermal processes differing in age and gave grounds for revising the age of granites pertaining to the Urulyungui Complex and refining the age of the Unda Complex.