Modern sedimentation processes in glacial lakes on the Spitsbergen archipelago (on the example of Lake Bretjørna)

The paper reviews the study results of sedimentation and formation of geochemical characteristics of glacial Lake Bretjørna sediment – as the example of postglacial process in inner areas of Arctic archipelagos. Field research and sampling were carried out in the winter of 2018. The properties of sediments along the profile of the lake were analyzed. The income and accumulation of heavy metals in sediment were assessed. The lithofacies characteristics of the sediments and their spatial distribution were determined. In the paper the main geochemical characteristics of the lake bottom sediments (granulometric composition, organic matter content, as well as the accumulation of Pb, Zn, Cu, Ni, Fe, Mn, Hg) are considered. The correlation between the lithological composition of sediments and their micro-component content are shown. Correlation between elements and terrigenous sediments income from Northern Scandinavia and the Kola Peninsula accumulated by the glacier and snow cover of the catchment is obtained. Three associations of trace elements in the group of studied elements are distinguished.

Geophysical constraints on the properties of a subglacial lake in northwest Greenland

In this study, we report the results of an active-source seismology and ground-penetrating radar survey performed in northwestern Greenland at a site where the presence of a subglacial lake beneath the accumulation area has previously been proposed. Both seismic and radar results show a flat reflector approximately 830–845 m below the surface, with a seismic reflection coefficient of −0.43 ± 0.17, which is consistent with the acoustic impedance contrast between a layer of water and glacial ice. Additionally, in the seismic data we observe an intermittent lake bottom reflection arriving between 14–20 ms after the lake top reflection, corresponding to a lake depth of approximately 10–15 m. A strong coda following the lake top and lake bottom reflections is consistent with a package of lake bottom sediments although its thickness and material properties are uncertain. Finally, we use these results to conduct a first-order assessment of the lake origins using a one-dimensional thermal model and hydropotential modeling based on published surface and bed topography. Using these analyses, we narrow the lake origin hypotheses to either anomalously high geothermal flux or hypersalinity due to local ancient evaporite. Because the origins are still unclear, this site provides an intriguing opportunity for the first in situ sampling of a subglacial lake in Greenland, which could better constrain mechanisms of subglacial lake formation, evolution, and relative importance to glacial hydrology.

Settlements and economy of the Funnel Beaker Culture communities. Archaeological and palynological evidence from the annually laminated lake bottom sediments (Gostynin Lake District, central Poland)

Palynological information preserved in pollen diagrams is of key importance for investigating prehistoric human activity. According to M. Ralska-Jasiewiczowa, of particular importance for assessing anthropopressure are results of the multidisciplinary research of annually laminated lake sediments carried out in Lake Gościąż and its surroundings in the Gostynin Lake District. In light of the results of human-environment analyses, the environmental disturbances recorded in laminated bottom sediments from Lake Gościąż can be described as reflecting pollen being “an account from afar”. In the analysed case, the pollen fallout may have originated from longer distances, and the recorded transformations of plant assemblages, both with respect to phase 5 and phase 6 from Gościąż, can be attributed to humans inhabiting up to 10 km from Lake Gościąż (e.g. around Lake Białe). On the other hand, the observations made in palynological sites of Białe, Lucieńskie, and Gąsak are well-correlated with the archaeological evidence of human activity. These diagrams reflect nearby activity, as the changes recorded in them correlate distinctly with the intensity of FBC settlement.

PAHs accumulation in soil-plant system in Atamanskoe lake bottom sediments in the long-term chemical contamination effect

<p>The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) in soils, under- and above-ground tissues of reed (Phragmites australis) on monitoring plots in the zone of industrial sewage tanks and sludge reservoirs in the city of Kamensk-Shakhtinskyi (southern Russia, Rostov Region), were determined. The total PAHs concentration in soil of monitoring site D3 (4229.4 ± 5.7<sup></sup>µg kg<sup>-1</sup>) was significantly higher than those in monitoring sites: D4 (3873.7 ± 17.1 µg kg<sup>-1</sup>), TR1 (2217.3 ± 9.1<sup></sup>µg kg<sup>-1</sup>), 43 (2001.1 ± 13.0<sup></sup>µg kg<sup>-1</sup>), and also D0 (140.4 ± 1.0<sup></sup>µg kg<sup>-1</sup>) plots. Accordingly, the maximum accumulation was found for phenanthrene among the 16 priority PAHs in the most of the soil and plants samples. It was determined the PAHs pollution effect in the studied monitoring sites on cellular and sub-cellular organelles changes of P. australis. The data received shows that increasing of PAHs contamination negatively affected on the cellular and sub-cellular organelles changes of the studied pants. Using of electron-microscopic method for plants sub-cellular structure showed ultrastructural changes in the cell membranes, and the main cytoplasmic organelles of plant cells. It was established the P. australis had a high level of adaptation to the effect of stressors by using of tissue and cell levels. In general, the detected sub-cellular alterations under the PAHs effect were possibly connected to changes in biochemical and histochemical parameters as a response for reactive oxygen species and also as a protective response against oxidative stress. The results received carry in innovative findings for cellular and sub-cellular changes in plants exposed to 16 priority PAHs as very persistent and toxic contaminants.</p><p>The research was financially supported by the Russian Science Foundation project no. 19-74-10046.</p>

Cleaning of oil-polluted bottom sediments of the boreal lake, Samotlor oil field, North Russia: case report

Small lakes in areas of intensive crude oil production may be susceptible to oil pollution arising from accidental spills and leaks, eventually leading to the pollution of bottom sediments. Effective cleaning of aquatic bottom sediments remains a challenge. Flotation is a potentially simple and reliable approach for the cleanup of bottom sediments without their excavation from the water body. Full-scale testing of flotation-based technology using the specially designed airlift plant allowed the cleaning of bottom sediments of an unnamed boreal lake (‘the lake’) within the Samotlor oil field, North Russia, heavily polluted with crude oil several decades ago. The lake bottom sediments are dominated by peat and unevenly polluted with oil. The average oil content in the lake bottom sediments was 111 g kg−1. During the 1.5 months' field test in July–August 2018, the average total oil concentration in the bottom sediments of the lake was reduced to 1.99 g kg−1. Secondary water contamination was minimal; the content of oil hydrocarbons in the water after completion of work did not exceed 0.09 ± 0.04 mg L−1. This study demonstrates that flotation-based technology can be applied for in situ cleaning of oil-contaminated lake bottom sediments including those in boreal climates.

Characteristics of hydrate-bound gas retrieved at the Kedr mud volcano (southern Lake Baikal)

We reported the characteristics of hydrate-bound hydrocarbons in lake-bottom sediments at the Kedr mud volcano in Lake Baikal. Twenty hydrate-bearing sediment cores were retrieved, and methane-stable isotopes of hydrate-bound gases (δ13C and δ2H of − 47.8‰ to − 44.0‰ V-PDB and − 280.5‰ to − 272.8‰ V-SMOW, respectively) indicated their thermogenic origin accompanied with secondary microbial methane. Powder X-ray diffraction patterns of the crystals and molecular composition of the hydrate-bound gases suggested that structure II crystals showed a high concentration of ethane (around 14% of hydrate-bound hydrocarbons), whereas structure I crystals showed a relatively low concentration of ethane (2–5% of hydrate-bound hydrocarbons). These different crystallographic structures comprised complicated layers in the sub-lacustrine sediment, suggesting that the gas hydrates partly dissociate, concentrate ethane and form structure II crystals. We concluded that a high concentration of thermogenic ethane primarily controls the crystallographic structure of gas hydrates and that propane, iso-butane (2-methylpropane) and neopentane (2,2-dimethylpropane) are encaged into crystals in the re-crystallisation process.

Estimation of the Range of Variation in the Mineral Composition of Silicate Lake Bottom Sediments Using Data from XRD and XRF

A method is proposed for estimating the range of mineral group content in the cores of silicate bottom sediments of lakes based on the search for the minimum and maximum content of stoichiometric minals that make up the group of minerals, provided that the balance of the mineral composition and the content of elements in the sample is observed. The mineral components were determined using the method of qualitative X-ray phase analysis, the contents of the main rock-forming elements were determined by X-ray fluorescence analysis. Comparison with the results of quantitative X-ray phase analysis showed that the contents of mineral groups either lie in the range calculated in the extreme search procedure based on data on the element composition, or overlap with the calculated range within the measurement error. The systematic discrepancy between the results of calculating the range of content of the silicon dioxide phase and the results of quantitative X-ray phase determination of quartz observed for the samples under consideration is due to the presence of an X-ray amorphous phase of biogenic silica. The proposed method for estimating the range of mineral group content is easy to implement, uses the publicly available MS Excel software, and can be useful for estimating variations in mineral composition by core depth, in conditions of frequent shortages of individual sample material distributed between different methods of analysis

Palynology of Holocene Lake Baikal sediments

<p class="p1"><span class="s1">The Class@Baikal 2019 expedition led by UNESCO-Moscow State University Educational-Scientific Center for Marine Geology and Geophysics (the Department of Geology, Moscow State University Lomonosov) sailed several transects between the southern and central part of the Lake Baikal, Russia. Seismic profiles were made to map the lake bottom sediments and structures as well as several short piston cores were drilled. The drilling sites were located a) following a nearshore to offshore transect to study the sedimentary processes and b) in areas where mud volcanoes were located in the geophysical data. Intriguingly, the sediments retrieved from the cores contained a high amount of plant debris, such as wood and conifer needles. The present palynological study has been started with the goal to better understand the sedimentological processes resulting in these distinct horizons of plant fossil rich sediments. Another goal is to obtain a stratigraphic age for the mud clasts and the surrounding matrix sediments of the presumed mud volcano structures. The first sediment samples appear to be rich in pollen and spores which allows to establish a palynostratigraphic framework for the studied cores.</span></p> <p class="p2"> </p>