Over the recent few decades, due to climate warming and the continuing exploration of Arctic seas’ mineral resources, the scientific interest in contamination problems has deepened significantly. In this study, for the first time, we characterize the distribution features of 47 elements (major and trace elements, including heavy metals, metalloid As, and Cs-137 technogenic radionuclide) in surface bottom sediments from some areas of the Barents, Kara, Laptev, and East-Siberian Seas. The lithogenic material was the main factor that controlled variability in many elements (Be, Al, Ti, Cr, Ga, Rb, Sr, Y, Zr, Nb, Ba, REE, Pb, Th, U, W, and Cs). Among the hydrogenic processes, the formation of Fe and Mn oxyhydroxides has the greatest impact on the Mn, Fe, Co, Ni, Cu, Ge, and Mo, and insignificantly V and Sb, variability in sediments. These, along with minor to moderate values of enrichment factor (EF) for most elements, allowed us to conclude that the observed element distribution is related to predominantly natural processes of thermal abrasion, river-run, and atmospheric input. The exception is As, which exhibited the elevated EF (up to 20) in the western and central Kara Sea, as well as in the Vilkitsky Strait. Since no significant relationship between As and Fe andMn oxyhydroxides distribution was found, we may assume primarily an anthropogenic source of As, related to the peat and/or coal combustion. According to the criteria of Ecological Risks assessment, all the examined areas have a low degree of risk. Data on the specific activity of Cs-137 correspond to the background average values characteristic for these regions. The highest levels of Cs-137 concentration (Bq/kg) were detected in the sediments of the Ob and Yenisei Rivers’ estuaries.

A comprehensive examination of the elemental (including radionuclides and heavy metals), mineral, and grain-size composition of sediments from different areas of the Barents Sea was performed. Sediment cores were sampled in the Central Deep, Cambridge Strait (Franz Josef Land Archipelago), Russkaya Gavan’ Bay (Novaya Zemlya Archipelago), and Bear Island Trough. We aim to evaluate how the modern and more ancient environmental conditions are reflected in the elemental and mineral composition, as well as to test indicative elemental ratios. The applied methods include elemental analysis using gamma-ray spectroscopy, X-ray fluorescence (XRF), Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), and X-Ray Difractometry XRD analysis of minerals. Difference in sedimentation rates, grain-size composition, and sources of material, are reflected in downcore variation of Si/Al, Mn/Fe, P/Al, Ti/K, and quartz-feldspar ratios. At boundary Early Holocene/Late Deglaciation, intensive bottom currents from the West-Southern shelf areas contributed to increase of Si/Al and Zr/Ca ratios. Distinct growth of the Si/Fe ratio within the sediments deposited over Late Pleistocene to Mid Holocene may be caused by increased contents of the coarse sand material, as well as by abundant fluxes of clay-mineral-loaded glacial meltwater during the main deglaciation phase. The Mn/Fe ratio used as redox proxy, displayed peaks at different depths related to oxygen concentration growth in bottom water.

The Piip Volcano is a submarine volcanic edifice occupying the central part of the Volcanologists Massif in the southwestern Bering Sea, with two tops, southern and northern. The minimum depth of the northern top is located at 368 m, and of the southern at 464 m. Active hydrothermal venting occurring at both summits of the volcano supports diverse biological communities, including animals specific for chemosynthetic habitats. In benthic organisms inhabiting the northern and southern tops of the Piip Volcano, for the first time, we examined distribution patterns of the following trace elements: titanium, vanadium, chromium, manganese, iron, nickel, copper, zinc, arsenic, selenium, zirconium, molybdenum, silver, cadmium, antimony, barium, tungsten, lead, bismuth, and uranium. The element contents were quantified by the ICP-MS. Total carbon (TC) and total inorganic carbon (TIC) were determined using a Shimadzu TOC-L-CPN and mineral composition of sediment was determined using the XRD. In the water of the biotope from the northern top, concentrations of Mn, Zn, Ag, Cd, Sb, W, Pb were 2–6 times, and Ba was 50 times higher than those from the southern top. This was attributed to the lower temperature of fluids emanating at the southern top. An abundant population of Calyptogena pacifica (Bivalvia: Vesicomyidae: Pliocardiinae) was found only at the southern top. The main target of most trace elements, such as Fe, V, Cr, Co, Ni, Zn, As, Mo, Ag, Cd, W, Pb, Bi, and U were the soft parts of Calyptogena pacifica (with high TOC content, on average 53.1% in gills and 49.6% in the rest of the body). Gills were characterized by particular high contents (>100 µg g⁻¹ dry w.) of Zn, Cd, Fe, Ni, Cu, and Pb, which can form sulphides or be associated with them. Shells of C. pacifica, as well as Brachiopoda, were depleted in these elements, as well as tissues of the carnivores Paguridae (Crustacea) and Actiniaria (Anthozoa). In suspension feeders from both tops, the lower contents of most elements were detected. Estimation of Biological Concentration Factor (BCF) for most elements varied from 10² to 10⁴, reaching n10⁵ for Ni, Zn, Ag, Cd, and Pb. A significant difference in BCF values between Fe and Mn was revealed.

In this study, to better understand the influence of hydrothermal processes on ore metal accumulation in bottom sediments, we examined distribution of Fe, Mn, Cu, Zn, As, and Pb in core of metalliferous sediments from the Pobeda hydrothermal cluster, and in core of non-mineralized (background) carbonate sediments (located 69 km northwards). Mechanisms of Fe, Mn, Cu, and Zn accumulation in sediments (12 samples) were evaluated based on sequential extraction of geochemical fractions, including a conditional mobile (F-1, exchangeable complex; F-2, authigenic Fe-Mn oxyhydroxides and associated metals; F-3, metals bound to organic matter/sulfides), and residual (F-4), fixed in crystalline lattices ones. The element contents were determined by the XRF and AAS methods, total carbon (TC) and total organic carbon (TOC) were determined using a Shimadzu TOC-L-CPN. Mineral composition and maps of element distribution in sediment components were obtained using the XRD and SEM-micro-X-ray spectrometry methods, respectively. In metalliferous sediments, according to our data, the major Fe mineral phase was goethite FeOOH (37–44% on a carbonate-free basis, cfb). In the metalliferous core, average contents (cfb), of Fe and Mn were 32.1% and 0.29%, whereas those of Cu, Zn, Pb, and As, were 0.74%, 0.27%, 0.03%, and 0.02%, respectively. Metalliferous sediments are enriched in Fe, Cu, Zn, Pb, and As, relatively to background ones. The exception was Mn, for which no increased accumulation in metalliferous core was recorded. Essential mass of Fe (up to 70% of total content) was represented by the residual fraction composed of crystallized goethite, aluminosilicates, the minerals derived from bedrock destruction processes mineral debris. Among geochemically mobile fractions, to 80% Fe of the (F-1 + F-2 + F-3) sum was determined in the form of F-2, authigenic oxyhydroxides. The same fraction was a predominant host for Mn in both metalliferous and background sediments (to 85%). With these Fe and Mn fractions, a major portion of Cu, Zn, and Pb was associated, while a less their amount was found in sulfide/organic fraction. In the metalliferous sediment core, maximal concentrations of metals and their geochemically mobile fractions were recorded in the deeper core sediment layers, an observation that might be attributed to influence of hydrothermal diffused fluids. Our data suggested that ore metals are mostly accumulated in sediment cores in their contact zone with the underlying serpentinized peridotites.

—It is shown that a large number of organic compounds of autochthonous and allochthonous nature are formed in the bottom sediments of separating waterbodies in the Kandalaksha Gulf of the White Sea, despite their subarctic position. The average content of C_org, N_tot, S_tot, aliphatic hydrocarbons, and polycyclic aromatic hydrocarbons in the bottom sediments are 5.33, 0.78, 0.53%, 817 μg/g, and 261 ng/g, respectively, which are significantly higher than in sediments of the open areas of the White Sea. The eutrophication of these waterbodies depends on their connection with the sea. It was found that anoxic pelitic sediments of separating lakes are enriched in Cu, Cd, Mo, Hg and U compared to sediments of the open sea bays in Kandalaksha Gulf. Thereby, the Hg and Mo contents are 2 and 14 times higher than their maximum permissible concentrations (MPC) (0.3 and 3 µg/g, respectively). A positive correlation with total sulfur (r > 0.8, р < 0.01) indicates the prevailing occurrence of these metals in form of poorly soluble sulfides.