Efficiency of stimulating precipitation from convective clouds using salt powders

Comparative estimates of the efficiency of hygroscopic reagents for the seeding of convective clouds to obtain additional precipitation are performed based on numerical simulation. It is shown that the use of polydisperse salt powders has many benefits over other known hygroscopic reagents. The effect of seeding with salt powders manifests itself at mass concentrations of hygroscopic particles an order of magnitude less than when pyrotechnic flares are used. With salt-powder seeding, it is possible to obtain precipitation from warm convective clouds of moderate thickness from which precipitation does not typically fall. In this case the effect of “reseeding” of clouds, which can be observed in seeding with hygroscopic reagents having narrow size distributions of particles, does not reveal itself.     

Experimental investigations of the effect of cloud-medium modification by salt powders

The results of experimental investigations into the action of polydispersion salt powders on model cloud media are presented. The results of experiments show a considerable positive effect of the modification of convective clouds by salt powders in order to obtain additional precipitation. The introduction of polydispersion salt powder into a forming cloud medium leads to the appearance of large cloud droplets and to the droplet-spectrum broadening. This result is a positive factor for the stimulation of coagulation processes and further precipitation formation. No “overseeding” phenomenon (when, instead of the enlargement of droplets, their sizes decrease and the concentration of cloud droplets increases) is observed at rather high mass concentrations of the introduced powder.     

Phlogopite and phlogopite–amphibole parageneses in the lithospheric mantle of the Birekte terrane (Siberian craton)

Mantle xenoliths containing phlogopite and phlogopite–amphibole mineralization from kimberlites of the Kuoika field have been studied. Such xenoliths were found in two series of rocks: magnesian (Mg) pyroxenite–peridotite and Fe-type phlogopite–ilmenite hyperbasite. The ⁴⁰Ar/³⁹Ar phlogopite age (1600–1800 Ma) and Re–Os and oxygen isotope data in rocks and minerals of the first series of rocks allow us to suggest that Phl–Amph metasomatism of the lithospheric mantle under the Birekte block and its accretion to the Siberian craton occurred in the subduction zone. The second series of rocks is comagmatic to potassium ultramafites and mafites, finding in the Siberian Platform. The phlogopite ages (870–850 Ma) from Phl–Ilm ultramafites corresponds to the beginning of the breakup of the supercontinent Rodinia and is close to ancient age datings of the alkaline ultramafic-carbonatite Tomtor massif. Phlogopite from xenoliths with garnet is much younger in age (500–600 Ma).

     

Possibilities of interpretation of the magnetotelluric data,obtained on a single profile over 3D resistivity structures

Magnetotelluric soundings are frequently carried out on a single profile or on profiles remote from each other. Interpretation of the obtained data is difficult in the presence of spatially heterogeneous geoelectric structures. We evaluate its capabilities on the basis of the synthetic data, that correspond to a geoelectric model, which consists of a three-layered section in the background and three rectangular prisms, differently arranged relative to the profile. Using the simple methods of analysis of magnetotelluric data, we succeeded in allocating all three heterogeneities over the area that surrounds the profile of observations. As a result of the fast smoothed-structure 1D and 2D inversion of different components of data, taking into account their specific features, the depths of the occurrence of anomalies and the order of the values of their electrical resistivity were evaluated, and the background section was also reconstructed. On this basis, and, also, with the use of a priori geological-geophysical information, the construction of a 3D model in a more or less broad band around the profile and its correction with the aid of 3D data inversion are possible.     

Physicochemical parameters of the melts participating in the formation of chromite ore hosted in the Klyuchevsky ultramafic massif,the Central Urals,Russia

The results of melt inclusion study are reported for chromites of the Klyuchevsky ultramafic massif, which is the most representative of all Ural ultramafic massifs localized beyond the Main Ural Fault Zone. The massif is composed of a dunite-harzburgite complex (tectonized mantle peridotite) and a dunite-wehrlite-clinopyroxenite-gabbro complex (layered portion of the ophiolitic section). The studied Kozlovsky chromite deposit is located in the southeastern part of the Klyuchevsky massif and hosted in serpentinized dunite as a series of lenticular bodies and layers up to 7–8 m thick largely composed of disseminated and locally developed massive ore. Melt inclusions have been detected in chromites of both ore types. The heated and then quenched into glass melt inclusions and host minerals were analyzed on a Camebax-Micro microprobe. The glasses of melt inclusions contain up to 1.06 wt % Na₂O + K₂O and correspond to melts of normal alkalinity. In SiO₂ content (49–56 wt %), they fit basalt and basaltic andesite. The melt inclusions are compared with those from chromites of the Nurali massif in the southern Urals and the Karashat massif in southern Tuva. The physicochemical parameters of magmatic systems related to the formation of disseminated and massive chromite ores of the Klyuchevsky massif are different. The former are characterized by a wider temperature interval (1185–1120°C) in comparison with massive chromite ore (1160–1140°C).     

Short intense bursts in magmatic activity in the south of Siberian Platform (Angara-Taseeva depression): the paleomagnetic evidence

Based on the paleomagnetic study of intrusive and explosive Permian-Triassic traps in the Angara River basin, Siberian Platform, it is established that the formation of the traps was marked by three short and highly intense bursts in magmatic activity, which resulted in the intrusion of three large dolerite sills (Tolstomysovsky, Padunsky and Tulunsky) and the deposition of the tuffs of the Kapaevsky Formation. These magmatic bursts occurred against the long-lived less intense background magmatism, which caused the formation of small intrusive bodies and tuff sequences. The geochronological data and correlation of the Angara traps to the effusive trap sequences in the north of the Siberian Platform (Norilsk and Maymecha-Kotuy regions) indicate that intrusion of the Tolstomysovsky sill and eruption of its comagmatic tuffs of the Kapaevsky Formation occurred in the Early Triassic. The obtained paleomagnetic data contradict the existing idea that the Padunsky and Tulunsky sills are coeval. Moreover, these data show that the magmatic bodies of different ages were mistakenly referred to the same sill.     

Equilibrium-nonequilibrium states of ornithogenous geosystems in the north pacific islands

An analysis is made of the issue related to the structural-functional organization of ornithogenous geosystems evolving in islands with large maritime colonial bird nest clusters. It is shown that under moderate ornithogenous pressure (Talan Island), the long-term vital activity of birds acts as an ecological factor identical to light, heat and atmospheric precipitation, and the geosystem is in an equilibrium state. In the case of a strong impact exceeding the stability threshold (Shelikan Island), the geosystem switches to a nonequilibrium state, which is accompanied by a degradation of the soil-vegetation cover, a mass extinction of ornithophobic plant species, a change in soilformation directedness, and by a most dramatic development of erosion processes.     

Ice- and cryogel-soil composites in water-retaining elements in embankment dams constructed in cold regions

There are a number of serious problems connected with building and repairing water-retaining elements in embankment dams in cold regions. One of them is the difficulty in finding inexpensive clay materials with the necessary structural properties and using them in the winter. Another is the cracks that appear in the upper part of a dam when the core freezes to the banks, and leakage along the cracks threatens to destroy the dam. Still another is the process of erosion at the bottom of the core which may occur through fissures in the rock foundation of a dam and in transport constructions. Also, the behaviour of water-retaining elements during earthquakes is unreliable. All of these problems can be solved by using ice- and cryogel-soil composites created by cryotropic gel formation (CGF). Our laboratory investigations demonstrate that the materials proposed for water-retaining elements have the necessary permeable, plastic, thermophysical, and strength properties to solve all of these problems. Certain constructions of water-retaining elements which may prove to be both safe and cost-effective are proposed. However, these ice- and cryogel-soil composites need to be field-validated before they are used in dams and transport structures in cold regions.     

Evaluation of equivalence between different methods for enumeration of fecal indicator bacteria before and after adoption of the new Bathing Water Directive and risk assessment of pollution

The quality of bathing water is of considerable public importance due to the possibility of fecal contamination. In 2009, Croatia implemented the new European Bathing Water Directive (BWD, 2006/7/EC) establishing stricter microbiological standards for new parameters with new reference methods. This study aims to evaluate the equivalence of different methods according to the old and revised BWD and to provide the possibility of data comparison. Furthermore, the directive requires the establishment of the bathing water profile (BWP) for pollution risk assessment. The estimation of consistency of pollution risk assessment with obtained microbiological results was also performed.     

Variant of more accurate determination of the locations of shortwave radio emission sources

The paper discusses how the trajectory calculation method can be used to solve the problem of locality determination of shortwave (SW) emission sources. The dependence of the electron concentration on the coordinates is specified using the SPIM model; it is corrected using the ionospheric solar activity index, which is specified with the help of maps of total electron content. We suggested a variant of how a regional map of the total electron content can be plotted according to measurements of signals from GLONASS/GPS navigation systems. It is shown that the trajectory calculation method, coupled with an adjustable ionospheric model, allows for a more exact locality determination of SW radio emission sources.