Grain-size and mineral composition of the upper layer of sediments of the Barents Sea

The paper presents data from grain size and mineralogical analyzes of surface bottom sediment samples obtained on several cruises of the R/V Akademik Mstislav Keldysh (2016–2018) from different parts of the Barents Sea. Pebble and gravel material is found in surface sediments in the form of impurities scattered throughout the sea. Such a chaotic distribution pattern is apparently associated with ice separation. Coarse material is most common in the Barents Sea off the coast of the Kola Peninsula, off the coast of Novaya Zemlya, Spitsbergen, where it accumulates due to coastal abrasion. In addition, a fraction >1 mm is widespread at depths where fine fractions are stirred and leached. The most common sediments in coastal shallow water are sands. Sands (0.1–1 mm) are widespread in the southern and southeastern regions of the sea, in the region of the Pechora polygon, the Kaninsky shallow water, the Kola Peninsula, and in the northwest, off the coast of Svalbard. With increasing depth, the sands are replaced by mixed sediments with a low admixture of pelite. Pelitic sediments are prevalent in the central part of the sea. Precipitation with a pelitic fraction (<0.01 mm) of more than 50% occupy about 70% of the Barents Sea. They are widespread in deep-sea hollows and trenches, as well as in the numerous fiords of the North Island of Novaya Zemlya and Franz Josef Land. Surface sediments have a predominantly terrigenous composition; only at the border with the Norwegian Sea the proportion of biogenic material increases. The mineral composition of sediments is dominated by quartz and feldspars, clay minerals are mainly represented by illite, smectite and kaolinite.

Some geochemical features of the major element composition of the surface bottom sediments of the Barents sea

The results of determination of the major element composition of 34 surface bottom sediment samples of the Barents sea are presented in this chapter. The main sources of sedimentary material supply to the sea – river discharge, aeolian input and other – were considered. It was shown that the available own and literature data did not allow to obtain an adequate estimation of entering sedimentary material balance in the sea. The comparison of the compositions of bottom sediments (sands, aleurites, pelites) and of predominated in the sea basin rocks has demonstrated the prevailed terrigenous material input. The interdependences between all major elements in bottom sediments and their grain-size composition were considered in details. It was established that the well-known interrelationships with the politic sediment fraction took place for all elements except Mn – increasing their contents along with growth of pelitic fraction. The exception is SiO2 and CaO, they demonstrated the highest content in the coarse fractions. The Mn behavior is unusual one. Mn concentrations in the sediments of the south-western part of the sea is almost independent on the share of the pelitic fraction that is very unexpected. At the same time the sediments from the north-eastern part of the sea are very enriched by Mn – up to 1.0−1.5%. The probable reasons of such type of this metal distribution in the sediments are discussed. On a base of the results available the fragmental maps of Al, Fe and Mn oxides distribution in the bottom sediments were constructed. The conclusion was made that our new data supported the classical type of the prevailed terrigenous sediment formation in the Barents Sea.

Distribution of radionuclides in modern sediments of the rivers flowing into the Dnieper-Bug Estuary

The article presents the results of large-scale studies of the content and distribution of natural and man-made radionuclides in the sediments of the rivers flowing into the Dnieper-Bug estuary. The article also presents the results of the granulometric analysis of the surveyed water bodies. The data about natural radioactive elements in the sediments rivers flowing into the Dnieper-Bug estuary obtained in this research are demonstrated moderate specific activity, which, however, clearly correlates with the granulometric composition of sediments. The 137Cs determined by us is contained in the sediments of all studied water bodies and the places of it greatest concentration coincide with the areas in which the sediment is represented mainly by the pelitic fraction. The data obtained in this research can serve as a baseline data in natural radionuclides concentration in sediments rivers flowing into the Dnieper-Bug estuary. The obtained data can also be used for further monitoring of the specific activity of man-made radionuclides, in particular 137Cs.

Clay minerals from rock salt of Bahadur Khel Formation, Eocene, Pakistan

According to studies of the pelitic fraction of the water-insoluble residue of 10 samples of Eocene rock salt of the Bahadur Khel Formation (Pakistan), it was determined that the clay minerals association contains swelling chlorite, chlorite-smectite, illite and kaolinite; chlorite was identified in three samples. Non-clay minerals are represented by quartz, dolomite, less often – magnesite; one sample contains impurities of both carbonates. Swelling chlorite, chlorite and mixed-layer minerals are trioctahedral, and illite and kaolinite are dioctahedral. All identified clay minerals, with the exception of kaolinite, are authigenic. The presence of swelling chlorite in Eocene rock salt is probably caused by changes in the concentration of brines in the basin against the background of complex geological processes of this era (climate change from thermal maximum to global cooling, changes in water circulation in oceans, changes in isotopic composition of carbonates). The association of clay minerals of Eocene rock salt, taking into account the peculiarities of its composition and the presence of swelling chlorite in it, we attributed to that formed during the SO4-rich seawater chemical type. This is also confirmed by two finds of swelling chlorite in the Triassic evaporites (rock salt of the Western Moroccan Basin, Midland marl) described in the literature, which are known to have been deposited from SO4-rich seawater. The presence of kaolinite in almost all samples is caused by its largest accumulation in sediments of this time period – terrigenous kaolinite came in large quantities from dry land and did not transform even at the stage halite precipitation. Full Text Keywords clay minerals, swelling chlorite, rock salt, Eocene, Bahadur Khel Salt, Pakistan.

ASSESSMENT OF THE HEAVY METAL POLLUTION LEVEL OF THE RIVER SEDIMENTS IN THE EAST DONBASS (ROSTOV REGION, RUSSIA)

Introduction. River bottom sediments are a significant link in the biogeochemical cycles of water bodies and an accumulator of pollutants. The purpose of this study is to assess the level of heavy metal pollution of river sediments within the coal-mining areas of the East Donbass (Rostov Region, Russian Federation) to assess the potential risk for the population using surface water as a source of water supply. Methods. It is suggested to use the pelitic fraction for a more accurate assessment of the heavy metal pollution level of river sediments. It is proposed to use the average continental shale concentration as a baseline value for the pelitic fraction. Contamination factor (Cf), degree of contamination (Cd) and geo-accumulation index (Igeo) were used to assess the degree of heavy metal pollution of the bottom sediments in the East Donbass rivers. Results. Studies of the chemical composition and the level of bottom sediments pollution in the East Donbass rivers showed that the concentration values of heavy metals vary greatly. Assessing the degree of heavy metal pollution of the river sediments in the East Donbass allows us to classify them mainly as moderately contaminated (uncontaminated to moderately contaminated). At the same time, the level of river sediments pollution in the Seversky Donets basin is generally lower than that in the Tuzlov basin. Conclusion. The results will be used to improve the system for assessing water and bottom sediments quality in the region as well as evaluate the environmental risk to public health. Although the results showed a moderate level of heavy metal contamination of the East Donbass rivers sediments, the potential hazard of secondary pollution of the aquatic environment with metals deposited in sediments remains. Pollution of water and river bottom sediments is directly linked to the potential risk to public health because these rivers are used as sources of drinking water for towns and countryside.

Occurrence, origin, and significance of melagranites in the South Mountain Batholith, Nova Scotia

Melagranites (colour index > 20, with biotite > garnet > cordierite) constitute ∼0.1% of the area of the 7300 km2 peraluminous South Mountain Batholith (SMB), Nova Scotia. The melagranites occur as small bodies showing sharp to gradational contacts against the Meguma Supergroup country rocks, and coeval mingling contacts against other facies of the batholith. They also occur as elliptical or blocky metre-scale enclaves elsewhere in the SMB. Characteristic petrological features of the melagranites include high modal abundances of sulphide minerals, strongly reacted metasedimentary xenoliths, mafic mineral-rich clots, apparent porphyritic textures with highly variable proportions of alkali feldspar megacrysts, and allotriomorphic-granular textures. Chemically and isotopically, melagranite rocks have wide compositional variations. In most major-element, trace-element, and isotopic variation diagrams, the melagranites lie on mixing lines between the more abundant granodioritic and monzogranitic phases of the SMB and the metasedimentary rocks of the Meguma Supergroup. Textural evidence, supported by published experimental evidence, suggests that the garnet, cordierite, and K-feldspar are peritectic phases resulting from incongruent melting of the pelitic fraction of the Meguma metasedimentary country rocks. The field relations, mineral assemblages, textural features, and chemical compositions of the melagranites all point to the melagranites as highly concentrated contamination zones in the SMB, representing small portions of the batholith that have failed either to complete the assimilation process or to disperse their contaminants widely in the batholith. As such, these rarely preserved melagranites provide petrogenetic information disproportionate in importance to their abundance in the batholith, especially about the significant role of contamination and assimilation in determining the physical and chemical composition of the SMB. Without preservation of melagranites in the SMB, and by extension all granite bodies, the petrogenetic importance of contamination is difficult to assess, even with trace-element and isotopic data. The present study shows that high quality field observations are as important in deciphering petrogenesis as chemical data.

Studies on the Contamination Status of the Danube River Basin Waters, Measures of Protection, and Rational Exploitation of the Water Resources

The water quality of the surface and ground waters, and the characteristics of the aquatic organism communities of the Yugoslav stretch of the River Danube were investigated. River flow rates were estimated according to recorded water levels and the hydrodynamic and morphological characteristics of certain profiles, and by using a mathematical model which included operation of the Djerdap Hydroelectric Power Station (HEPS). During May 1986, water flow rates were 3200 to 6000 m3/s, and in September they were two, times slower. All physical and chemical parameters were determined using standard Yugoslav and German methods (DEV). Regarding the 14 metals analysed, the water samples were satisfactory, while the contents of metals in the pelitic fraction (i.e., diameter ≤ 2 µm) of the sediments indicated the existence of pollution. The pelitic fraction of the sediments was subjected to trace element analysis by an emission spectrographic technique using germanium as the internal standard. The overall precision was ± 12%. Water ecosystem saprobity was estimated according to Pantle-Buck and Roth-schein. The saprobity ranged from beta to alpha-betamesosaprobity. The contents of trace elements in the water, sediment, and aquatic communities indicated the transfer of pollutants between the various ecosystem compartments.