Research Results on Ecological Hazard Objects in Abrosimov Bay (Novaya Zemlya,Kara Sea)

Oceanology - The article presents results of field research on environmental assessment in Abrosimov Bay (Yuzhny Island of Novaya Zemlya) in connection with the existing RW disposal sites in this...     

Anaerobic oxidation of methane (AOM) in marine sediments from the Skagerrak (Denmark): II. Reaction-transport modeling

A steady-state reaction-transport model is applied to sediments retrieved by gravity core from two stations (S10 and S13) in the Skagerrak to determine the main kinetic and thermodynamic controls on anaerobic oxidation of methane (AOM). The model considers an extended biomass-implicit reaction network for organic carbon degradation, which includes extracellular hydrolysis of macromolecular organic matter, fermentation, sulfate reduction, methanogenesis, AOM, acetogenesis and acetotrophy. Catabolic reaction rates are determined using a modified Monod rate expression that explicitly accounts for limitation by the in situ catabolic energy yields. The fraction of total sulfate reduction due to AOM in the sulfate-methane transition zone (SMTZ) at each site is calculated. The model provides an explanation for the methane tailing phenomenon which is observed here and in other marine sediments, whereby methane diffuses up from the SMTZ to the top of the core without being consumed. The tailing is due to bioenergetic limitation of AOM in the sulfate reduction zone, because the methane concentration is too low to engender favorable thermodynamic drive. AOM is also bioenergetically inhibited below the SMTZ at both sites because of high hydrogen concentrations (∼3-6 nM). The model results imply there is no straightforward relationship between pore water concentrations and the minimum catabolic energy needed to support life because of the highly coupled nature of the reaction network. Best model fits are obtained with a minimum energy for AOM of ∼11 kJ mol⁻¹, which is within the range reported in the literature for anaerobic processes.     

The scope for generating bio-oils with relatively low oxygen contents via hydropyrolysis

The primary oils obtained in high yields from fast (fluidised-bed) pyrolysis of biomass generally have high oxygen contents (ca. 40% w/w). The scope for using pyrolysis under hydrogen pressure (hydropyrolysis), to give oils with much lower oxygen contents compared to normal pyrolysis has been investigated. Fixed-bed hydropyrolysis tests have been conducted on cellulose, sugar cane bagasse and eucalyptus wood using hydrogen pressures up to 10 MPa, with heating rates of 5 and 300°C min⁻¹. A colloidal FeS catalyst was used in some tests (Fe loading of 5%, w/w) to increase overall conversions. Further, the attractive option of using a two-stage reactor in which the primary oil vapors are passed though a bed of hydrotreating catalyst is also described. Raising the hydrogen pressure from atmospheric to 10 MPa reduced the oxygen content of the primary oil by over 10% to below 20% w/w. The addition of a dispersed iron sulphide catalyst gave conversions close to 100% for all three biomass samples investigated at 10 MPa under conditions in the fixed-bed reactor where significant diffusional resistances existed and reduced the oxygen content of the bio-oil by a further 10%. Although NMR indicated that the oils became increasingly aromatic as more oxygen was removed, the increase in hydrogen pressure decreased the extent of overall aromatisation that occurs primarily due to the lower char yields obtained. In two-stage tests for cellulose, using a commercial sulphided Ni/Mo γ-Al₂O₃ catalyst at 400°C, increasing the hydrogen pressure from 2.5 to 10 MPa decreased the oxygen content of the oil by over 20% to 10% w/w. The H/C ratios were higher and O/C ratios smaller for the two-stage bio-oils compared to their single stage counterparts. However, the differences in the O/C ratios between the single and two-stage bio-oils increase with pressure.     

Earthquake resistant construction techniques and materials on Byzantine monuments in Kiev

The study of the behaviour of historic buildings that have suffered from earthquakes has become a valuable tool for the understanding of earthquake resistant construction techniques and materials. Byzantine monuments of the 11–13th century in Kiev have been studied to provide insights into their effective dynamic properties facing severe earthquake history in the area. The recessed brickworks according to the “concealed course” construction technique of the St. Sophia Cathedral (11th century), the Church of St. Michael in the Vydubytskyi Monastery (11th century), the Tithe Church of the Assumption of the Virgin (10th century) and the Cathedral of Assumption of the Virgin (11th century) in the Monastery of the Caves (Pecherskyi monastery) in Kiev were studied and the material properties of bricks and lime mortars with ceramic fill were investigated (mechanical strength tests, mineralogical, chemical and microstructural analysis). The results show major similarities with those of the Byzantine monuments in Istanbul (Theodosian Walls and Hagia Sophia — 6–11th century construction phases), giving evidence of earthquake resistant construction techniques and materials allowing for continuous stresses and strains. Hence, didactics on proper restoration techniques and materials are deduced aiming at their present safety in the face of future earthquakes.     

Couplage des équations de transfert de masse et des lois d''interactions solution-solide par l''utilisation des lanthanides comme traceurs — Approche expérimentale

In underground flow tracing studies, the estimation of the nature and the importance of interactions undergone by the substance used very often constitutes an obstacle to good modeling of mass-transfer processes in solution.

We propose a method to quantify these phenomena by the use of lanthanides as tracers.

For this study, we set up an analytical methodology adapted to routine measurements. The quality of five lanthanides as indicators has been examined. We have demonstrated the formation, by substitution, of a carbonate complex which is extremely stable in the natural environment. The field experiments carried out demonstrated the efficiency of those tracers and confirmed their great stability.

Tracer recovery graphs show that, in accord with our hypothesis, convection and dispersion are identical for all the lanthanide elements. Moreover, we have established a direct relation between their fixing rate on earth materials and the value of their stability constants.

Thus, we demonstrate the possibility of correlative multitracing, with known and quantifiable interelement relations.

Résumé

Dans les études de circulations souterraines par traceur, l'estimation de la nature et de l'importance des interactions subies par la substance utilisée constitue, bien souvent, un obstacle à une bonne modélisation des processus de transfert de masse en solution.

Nous proposons une méthode de quantification de ces phénomènes par l'utilisation des lanthanides comme traceurs.

Pour cette étude, nous avons mis au point une méthodologie analytique adaptée aux mesures de routine. Les qualités, en tant qu'indicateurs, de cinq lanthanides ont été examinées. Nous avons démontré la formation, par substitution, d'un complexe carbonaté extrèment stable en milieu naturel. Les expériences de terrain réalisées ont prouvé l'efficacité de ces traceurs et confirmé leur grande stabilité.

Les courbes de restitution obtenues ont montré que, conformément à nos hypothèses, la convection et la dispersion sont identiques pour l'ensemble de ces éléments. De plus, il a été établi une relation directe entre leurs taux de fixation sur le terrain et la valeur de leurs constantes de stabilité.

On dispose ainsi d'une possibilité de multitraçage corrélatif, avec des relations interélémentaires connues et quantifiables.     

Seasonal snowline instability in an energy balance model

The stability properties of a seasonal, one dimensional energy balance climate model are examined. The model contains idealized landsea geography, an interactive moving snowline and high space-time resolution. For a polar land cap surrounded by ocean we find a bifurcation in the seasonal cycle solutions as a function of solar constant leading to qualitatively different climate regimes: one with continental snow-free summers and the other with perennial snow cover over a large area surrounding the pole. In the parameterspace neighborhood of a bifurcation an infinitesimal change in any radiation budget parameter can cause the transition from one state to the other. Of special interest to those planning more elaborate numerical experiments (GCMs) is the result that 10s of seasonal cycles may be necessary for the model to damp out transient effects before settling upon a repeating seasonal cycle if parameter values are such that the solution is near a bifurcation. This latter finding is unexpected, since the longest time scale in the linear version of the energy balance model is about 5 years.     

Factors and characteristics of the spatial correlation of the annual runoff of the Upper Ob basin rivers

The main features of the spatial and temporal oscillations of the annual runoff of the rivers in the Upper Ob basin, which is characterized by various landscape and hydrologic conditions, are discussed. It is found that the coefficients of pair correlation of the annual runoff have been decreasing since the late 1990s-early 2000s. Correlation functions for mountain areas should be constructed separately for river basins ranked according to the prevailing type of river feed. The coefficients of pair correlation can be described by multiple regression equations, which, apart from the distance between the centers of gravity of the basins, may include landscape characteristics such as the difference in their average elevation and forest cover.     

Seismic observations at an overstep of the western North Anatolian Fault (Abant–Sapanca region, Turkey)

The course of the active North Anatolian Fault system from Lake Abant to Lake Sapanca was traced by its high micro-earthquake activity. If approaching from the east this section includes a broad south to north overstep (fault offset) of the main fault. Local seismicity has been recorded in this area by a semi-permanent network of 8 stations since 1985 within the frame of the Turkish–German Joint Project for Earthquake Research. The effect of the overstep and its complex fracture kinematics are reflected by the seismicity distribution, the variations of composite fault-plane solutions, and by the spatial coda-Q distribution. Areas of different stress orientation can be distinguished and assigned to different groups of faults. The stresses and the tectonic pattern only in part correspond to a simple model of an extensional overstep and its correlative pull-apart basin. Other types of deformation involved are characterized by normal faulting on faults parallel to the general course of the main strike-slip fault and by synthetic strike-slip faults oriented similar to Riedel shears. Shear deformation by this fault group widely distributed in an area north and east of the main fault line may play an important role in the evolution of the overstep. The development of a pull-apart basin is inhibited along the eastern half of the overstep and compatibility of both strands of the main fault (Bolu–Lake Abant and Lake Sapanca– Izmit–Marmara Sea) seems to be achieved with the aid of the fault systems mentioned. The extension of the missing part of the pull-apart basin seems to be displaced to positions remote from the Lake Abant–Lake Sapanca main fault line, i.e. to the Akyaz?–Düzce basin tract. Highest Q-values (lowest attenuation of seismic waves) were found in the zone of highest seismicity north and west of the overstep which is the zone of strongest horizontal tension. If high coda-Q is an indicator for strong scattering of seismic waves it might be related to extensional opening of fractures.     

The gas emission spectrum in a star-forming region in the BCD galaxy VII Zw 403 (UGC 6456)

Observations with the 6-m telescope of the Special Astrophysical Observatory obtained with the MPFS panoramic spectrograph and a slit spectrograph with the SCORPIO focal reducer are used to analyze the emission spectrum of the ionized gas in a star-forming region in the BCD galaxy VII Zw 403. We present images of the galaxy’s central region in Hα, Hβ, [SII], and [OIII], together with maps of the relative [OIII]/Hβ and [SII]/Hα intensities. We have determined the parameters of the gas in bright ionized supershells, and estimated the relative abundances of oxygen, nitrogen, and sulfur; a low relative N/O abundance was detected.