Copper (II) Speciation in a Freshwater Ecosystem

Results of chemico-biological experiments in a natural water body with the use of model systems with Cu (II) introduced in them at different proportions of its chemical forms (natural and simulated) in the solution. The model forms used in the experiments were Cu complexes with benzyl- and hexadecylmalonic acids, simulating low-molecular dissolved organic substances. The experimental conditions were chosen based on a preliminary calculation using WATEQ–4f program. The complexes of Cu with hexadecylmalonic acid are found to be absorbed by suspensions and removed into bottom sediment more actively than other Cu forms. The toxicity of introduced Cu for the phyto- and zooplanktonic communities is found to depend on the concentration of Cu²⁺ aqua-ions in the solution, in the presence of which the higher concentrations of complexes with malonic acids do not exert their toxic effect.     

Isotope-geochronological (U-Th-Pb, Lu-Hf) study of the zircons from the archean magmatic and metasedimentary rocks of the Podolia domain, Ukrainian shield

Zircons from the oldest magmatic and metasedimentary rocks of the Podolia domain of the Ukrainian shield were studied and dated by U-Pb method on a NORDSIM secondary-ion mass spectrometer. The age of zircon cores in the enderbite gneisses taken in the Kazachii Yar and Odessa quarries on the opposite banks of the Yuzhnyi Bug River reaches 3790 Ma. Cores of the terrigenous zircons in the quartzites from the Odessa quarry as well as in the garnet gneisses from the Zaval’e graphite quarry have an age within 3650–3750 Ma. Zircon rims record two metamorphic events at 2750–2850 Ma and around 1900–2000 Ma. Extremely low U content in the zircons of the second age group indicates conditions of the granulite-facies metamorphism in the Paleoproterozoic within the Podolia domain. Obtained data on the orthorocks (enderbite-gneiss) and metasedimentary rocks unambiguously suggest the existence of ancient Paleoarchean crust in the Podolia (Dniester-Bug) domain of the Ukrainian shield. They contribute in our knowledge of scales of the formation and geochemical features of the primordial crust.     

MICROWAVE REMOTE SENSING AS A METHOD FOR ESTIMATING SNOW RESERVES IN FORESTS OF THE WESTERN SAYAN

A Russian-American team of remote sensing researchers investigates the applications of active microwave (synthetic-aperture radar) imagery for estimation of water reserves in snowpack in the Western Sayan Range of East Siberia. Considerable attention is devoted to an explanation of the study's principal finding—that a fundamentally different statistical relationship exists between strength of the reflected radar signal and snow cover depth in open areas versus forested areas with high levels of canopy closure. Translated by Edward Torrey, Alexandria, VA from: Geografiya i prirodnyye resursy, 1999, No. 4, pp. 85-90.     

The early crust beneath the Azov Domain of the Ukrainian Shield: Isotopic-geochronological and geochemical investigations of detrital zircons from metasedimentary rocks of the Fedorovka structure

The results of isotopic-geochronological investigations of detrital zircons from metasediments of the Fedorovka structure in the Azov Domain of the Ukrainian Shield by SIMS and LA-ICP-MS methods are considered. The data obtained are compared with the results of isotopic dating of zircons from metasediments of the Soroki greenstone structure of the Azov region. All the examined samples yielded zircons with ages exceeding 3600 Ma. The geochemical properties of the oldest zircons indicate that they originate immediately from tonalite rocks. The obtained data imply substantially wider development of the Paleoarchean crust in the Ukrainian Shield than was previously thought.     

Composition and structure of microaggregates in soils of the Behr hillocks, southern Astrakhan district

Study of the composition, structure and morphology of microaggregates less than 1 mm in size in soils of one of the Behr hillocks revealed a high share of the clay-salt segregations (microaggregates and cutans). It was established that the segregation type depends on the mud content in soil, while the packing of particles, as well as the size and morphology of microaggregates, depend on the content and properties of salts. The clay component in the microaggregates is mainly represented by smectite. Carbonate (calcitic, dolomitic, and ferruginous) clay-salt microaggregates were found in all horizons of the studied soils, except for horizon Ap on the subhillock plain in the former rice paddy. Gypsum clay-salt microaggregates were identified in the salic horizon Bs of soils. The microaggregates in solonchaks were formed with the contribution of Na-Mg-Ca chlorides and sulfates. The formation of clay-salt aggregates promoted high microstructuring of soils and stability of the Behr hillocks under arid climatic conditions.     

Terrigenous zircon of archean greenstone belts as a source of information on the early earth’s crust: Azov and Dnieper domains,Ukrainian shield

Zircons from the metasedimentary rocks of the Mesoarchean greenstone belts of the Azov and Middle Dnieper blocks of the Ukrainian shield were studied and dated by U-Pb method on a NORDSIM secondary-ion mass spectrometer. Detrital zircons from the metasediments of the Belozerskaya Formation of the greenstone belts of the Middle Dnieper block are usually dated within 3000–3100 Ma, while individual grains have an age of 3200–3300 Ma. This indicates that the sediments were derived mainly from proximal volcanic source with minor contribution of the basement material (Aul’skaya Group). The metasediments of the Soroki greenstone structure of the Azov block contain mainly zircons with ages within 3500–3600 Ma, except for scarce grains having the ages older than 3700 Ma. Zircon cores are overgrown by granulitic rims dated at approximately 3300 Ma. A wide scatter in ages and Th/U ratios in the zircons indicate that they were derived from rocks of different composition and age. Obtained data suggest significantly wider distribution of the Paleoarchean crust within the Azov block of the Ukrainian shield than was previously assumed.