V. A. Bobrov

On the elemental composition of suspended matter of the Severnaya Dvina River (White Sea region)

New data on the elemental composition of the Severnaya Dvina River, the largest one in the White Sea region, are presented. The elemental composition of the river water in May, the period of the snowmelt flood, is similar to the upper layer of the Earth’s continental crust due to the active erosion of the earth material in the catchment area. In August, the period of the summer low water, the impact of biogenic components increases and elevated concentrations of Cd, Sb, Mn, Zn, Pb, and Cu are observed. At other times, no significant pollution by heavy and rare-earth elements is registered.

Composition of the suspended particulate matter at the Severnaya Dvina River mouth (White Sea) during the spring flood period

The grain-size and mineral composition of the suspended particulate matter (SPM) of the Severnaya Dvina River mouth is studied, as well as the content of several lithogenic elements in the SPM during the spring flood in May 2004. The data published on the composition of the riverine SPM in the White Sea basin are very poor. The spring flood period when more than half of the annual runoff is supplied from the river to the sea in a short time is understood more poorly. The report considers the comparison results for the grain-size compositions of the SPM and the bottom sediments. The data of laser and hydraulic techniques of the grain-size analysis are compared. The short-period variations of the SPM concentration and composition representing two diurnal peaks of the tide level are studied. It is found that the SPM is mainly transferred during the spring flood as mineral aggregates up to 40 μm diameter. The sandysilty fraction of the riverine SPM settles in the delta branches and channels, and the bulk of the fine pelitic matter is supplied to the sea. The mineral and chemical composition of the Severnaya Dvina River SPM is determined by the supply of substances from the drainage basin. This substance is subjected to intense mechanic separation during the transfer to the sea. The key regularities of the formation of the mineral composition of the SPM during the flood time are revealed. The effect of the grain-size composition of the SPM on the distribution of the minerals and elements studied in the dynamic system of the river mouth are characterized.

Geochemical Characteristics of the Modern State of Salt Lakes in Altai Krai

A complex of analytical methods (atomic absorption spectroscopy AAS, synchrotron radiation X-ray fluorescence SR-XRF, and instrumental neutron activation analysis INAA) were used for analyses of 40 trace elements. In compliance with the conventional biogeochemical methods, enrichment factors EF were calculated for plankton relative to the average concentrations of elements in continental clay (shale) preliminarily normalized to Sc. In order to understand the concentration specifics of trace elements in living organisms inhabiting aquatic ecosystems of variable salt composition and geochemical characteristics, chemical speciation of elements was calculated for the brines of salt lakes by the WATEQ4F and Selektor-S computer programs. The enrichment of plankton in Hg in Lake Bol’shoe Yarovoe is caused not only by the chemistry of the mineralized brine (bittern), as follows from the Hg speciation in it, but also by anthropogenic contamination (Hg-bearing wastes from the Altaikhimprom chemical plants in the town of Yarovoe).

Biogenic Contribution of Minor Elements to Organic Matter of Recent Lacustrine Sapropels (Lake Kirek as Example)

An approximate biogenic contribution of minor elements to sapropel of Lake Kirek in West Siberia is estimated using the “model of direct inheritance” of their composition in plankton by OM of bottom sediments (Yudovich and Ketris, 1990). It is shown that the lifetime accumulation of P, Br, and Zn in copepod zooplankton of Lake Kirek notably affects the concentration of these elements in sapropelic mud (biogenic contribution is approximately 95–53%). The biogenic share of other elements in these sediments is substantially lower: approximately 30% for Sr and Ba; 26–16% for Ca, Pb, Cd, Cu, K, Mg, and Cr; and no more than 5% for As, Co, Fe, Ni, Ti, Y, and Mo.

Anomalous concentrations of zinc and copper in highmoor peat bog, southeast coast of Lake Baikal

When examining the peat deposit discovered in Vydrinaya bog, South Baikal region, the authors encountered anomalous Zn and Cu concentrations for highmoors being up to 600–500 ppm on a dry matter basis in the Early Holocene beds (360–440 cm) formed 11 000–8500 years ago. It has been demonstrated that Zn and Cu are present inside the plant cells of peat moss in the form of authigenic sulfide minerals of micron size. Apart from Zn and Cu, native Ag particles (5–7 um) have been encountered in the peat of the Vydrinaya bog at a depth of 390–410 cm; these particles formed inside the organic matter of the plasma membrane of peat moss containing Ca, Al, S, and Cu. This study suggests probable patterns of the formation of zinc sulfides, copper sulfides, and native silver in peat moss. The results obtained indicate that biogenic mineral formation plays a significant role in this system, which is a very important argument in the discussion on the ore genesis, in which physicochemical processes are normally favored, while the role of living matter is quite frequently disregarded.

Concentration of chemical elements by zooplankton of the White Sea

A technique of net sampling of zooplankton at night in the Kandalaksha and Dvinskii Bays and during the full tide in the Onezhskii Bay of the White Sea allowed us to obtain “clean” samples without considerable admixtures of terrigenous suspension. The absence of elements-indicators of the terrigenous suspension (Al, Ti, and Zr) in the EDX spectra allows concluding that the ash composition of the tested samples is defined by the constitutional elements comprising the organic matter and integument (chitin, shells) of planktonic organisms. A quantitative assessment of the accumulation of a large group of chemical elements (approximately 40) by zooplankton based on a complex of modern physical methods of analysis is presented. The values of the coefficient of the biological accumulation of the elements (Kb) calculated for the organic matter and the enrichment factors (EF) relative to the Clarke concentrations in the shale are in general determined by the mobility of the chemical elements in the aqueous solution, which is confirmed by the calculated chemical speciation of the elements in the inorganic subsystem of the surface waters of Onezhskii Bay.

Investigation into the elemental composition of sapropel from Lake Kirek (West Siberia) by SR XFA technique

The synchrotron radiation X-ray fluorescence analysis (SRXFA) technique was applied for scanning two sapropel cores: 6.2 m (coordinates of boring 56°11′93″ N, 84°23′22″ E) and 3.6 m (56°10′93″ N, 84°22′94″ E), obtained at a depth of 5 and 7 m, respectively, in Lake Kirek (southern part of Tomsk oblast, West Siberia). Based on variations in the content of eight chemical elements in stratified core horizons, the geochemical types of the sapropels and their prevalence were established. In the sediment of the 6.2-m core within the overall boundaries of the Holocene, low-ferric calcareous sapropel dominates, the geochemical characteristic of which is presented by the average values of 13 chemical elements in the strata grouped by the main climatic periods of the Holocene. Organic-ferrous sapropel 90 cm in depth was uncovered in the 3.6-m core in the range 215–305 cm (age of 7-4 ka). For the other core horizons, the deposit is represented by calcareous sapropel, but with higher contents of iron in comparison with the first type. The geochemical differentiation of these two types of sapropels (in 3.6-m core) is characterized by average contents of 31 chemical elements. The consistency of the compositions and concentrations of chemical elements in sapropels in the Holocene section of the deposits is evidence of the identical formation conditions for these types of sapropel.

Transformation of organic matter in the Holocene sediments of Lake Ochki (south Baikal region): Evidence from pyrolysis data

Transformation of organic matter (OM) in Holocene sediments of Lake Ochki (southern coast of Lake Baikal) at the early stages of diagenesis has been studied using pyrolytic methods of Rock Eval (RE-pyrolysis) and pyrolysis-gas chromatography-mass spectrometry (Pyr-GC-MS). OM has been analyzed in lacustrine sediments and their main producers, phytoplankton and zooplankton. Data on the distribution of hydrocarbon–biomarkers in sediments indicate an uninterrupted influx of terrigenous OM and transformation of OM precipitated by microorganisms. The analysis of molecular composition of pyrolysates makes it possible to assume a sharp change of sedimentation conditions in the upper part of sedimentary sequence (0–60 cm). It is shown that the macromolecular aliphatic kerogen structure begins to form in incoherent sediment at the very early stages of diagenesis.

X-ray fluorescence and electron microscopy study of plankton samples from the Novosibirsk reservoir

Five samples of plankton from the Novosibirsk reservoir are collected and analyzed by X-ray fluorescence. In combination with high sensitive atomic absorption spectroscopy (AAS), inductively coupled plasma mass spectrometry (ICP-MS), and instrumental neutron activation analysis (INAA), quantitative data on the concentrations of 52 chemical elements in plankton are obtained. Scanning electron microscopy is used to analyze the elemental composition of plankton samples from the Novosibirsk reservoir. This enables us to reveal the nature of the possible presence of minerals (of biogenic or terrigenous origin) that increase the ash content in the samples under study. The results of the studies provide an answer to the methodical question of whether the ash content of plankton samples is mostly determined by the presence of terrigenous elements in it or is in general formed by constitutional (biogenic) elements of skeletal and dermal tissues of planktonic organisms.

Mineralogical–Geochemical Features of Ice-Rafted Sediments in Some Arctic Regions

The quantitative mineral composition estimated using the Rietveld method and some geochemical features are considered for bulk samples of the ice-rafted sediments (IRS) from some Arctic regions. Layer silicates in the studied samples vary from ~20 to ~50%. They are dominated by micas and their decomposition products (illite and likely some part of smectites) at significant contents of kaolinite, chlorite, and transformation/decomposition products of the latter. A significant content of illite and muscovite among layer silicates in most IRS samples suggests that sources of the sedimentary material were mainly mineralogically similar to modern bottom sediments of the East Siberian and Chukchi seas, as well as presumably sediments of the eastern Laptev Sea. It is suggested that a significant kaolinite fraction in IRS samples from the North Pole area can be caused by the influx of ice-rafted fine-grained sedimentary material from the Beaufort or Chukchi seas, where kaolinite is supplied from the Bering Sea. Positions of IRS data points in the (La/Yb)N–Eu/Eu*, (La/Yb)N–(Eu/Sm)N, and (La/Yb)N–Th diagrams show that the studied samples contain variable proportions of erosion products of both mafic and felsic magmatic rocks and/or sufficiently mature sedimentary rocks. This conclusion is confirmed by localization of IRS data points in the Th/Co–La, Si/Al–Ce, and Si/Al–Sr diagrams.