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Mining regions in different parts of the world have been associated with the significant pollution of water, sediments, and soils by manganese and other chemical elements. This study assessed the degree of geochemical transformation caused by open-pit extraction and processing of mineral resources in the Kovdorsky District of Murmansk Oblast, 20 km from the Russia–Finland border. A second objective was to predict further changes co-driven by industrial pressure and high climatic instability in the polar region. The field study involved sampling water and sediments from virgin background streams and from the tailings storage facility, settling ponds, rivers, and lakes affected by ore mining and disintegration. Laboratory analyses included the study of elemental composition, redox potential, alkalinity and acidity, organic matter content, and other geochemical characteristics for a better understanding of pollutant migration patterns. We revealed elevated levels of potentially toxic elements in surface waters and bottom sediments which pose a risk to the human health via the household and drinking water supply. Pollution with manganese (Mn) was found to be the major environmental issue. Its natural presence in the river water was overridden a hundredfold by anthropogenic enrichment. This is problematic as Mn is easily bioaccumulated, which can lead to unwanted ecotoxicological effects, and—in the case of prolonged exposure to high doses of Mn and its compounds—to detrimental human health impacts. We believe that the changing climate may raise the water flow and thus expand the area of the hydrochemical anomaly. On the other hand, the activation of self-purification and dilution processes could lead to decreasing environmental Mn concentrations.

This study inverted the grain size of surface sediments on the seafloor in a route area of the eastern South China Sea based on sub-bottom profile data and discussed the impact of hard seabed and bottom sediment anomalies on the inversion results. The physical properties of seafloor surface sediments, such as grain size, porosity, and density, are important aspects of marine sedimentology research and marine engineering geological analysis. Inverting these physical properties through the Biot-Stoll model is one of the currently used methods. This inversion method requires the extraction of the seafloor reflection coefficient, while the presence of bottom sediment anomalies and hard seabed geomorphology in the study area may affect the accuracy of the extracted seafloor reflection coefficient. However, the impact of these two types of geomorphology on the accuracy of this inversion method is currently lacking in research. The inverted grain size obtained through a series of inversion calculations was compared with the actual measured grain size obtained from sampling, with a relative error of 2.31% to 29.31%. Analysis shows that hard seabed and bottom sediment anomalies affect the accuracy of the seafloor reflection coefficient, leading to larger errors in the inversion results near areas with such geomorphology. Therefore, in areas with hard seabed and bottom sediment anomalies, it may be suitable to use the inversion method of this study with high-resolution data by increasing the density of survey lines and sampling points to reduce errors caused by the impact of geomorphology. In addition, based on the characteristic that the seafloor reflection coefficient is affected in hard seabed and bottom sediment anomaly areas, it may be used as an auxiliary means to identify abnormal seafloor geomorphological areas, providing a reference for engineering disaster geological prevention.

The bottom sediments in catchment areas behind dams play a significant role in water ecosystems. On the other hand, the structure of sediments makes them a natural geosorbent, in which pollutants introduced to the aquatic environment accumulate. The use of biotests is recognised as an important approach for the assessment of the quality of bottom sediments, as the chemical analysis of sediment samples alone does not provide evidence of the impact of contaminants on biota. The aim of the study was to apply the chemical and ecological indices to determine the potential risk posed by trace elements in the bottom sediments and to evaluate sediment toxicity using organisms belonging to two taxonomic groups, i.e., plants (Phytotoxkit) and crustaceans (Rapidtoxkit). The 46 sediment samples were taken from the Rożnów Dam Reservoir in Southern Poland. The mean concentration of the trace elements in the sediments was 5.22 mg As; 0.26 mg Cd; 63.23 mg Cr; 28.65 mg Cu; 37.11 mg Ni; 11.15 mg Pb; 69.69 mg Zn and 0.09 mg Hg ∙ kg−1 d.m. The mean probable effect concentration quotient (PECq) value among different sampling sites ranged between 0.04 and 0.33 suggested moderate potential toxicity to the biological communities in bottom sediments. The Ni was potentially the most toxic element for biota in the Rożnów Reservoir. The sensitivity of organisms formed the following order: Thamnocephalus platyurus >Lepidium sativum >Sinapis alba >Sorghum saccharatum. For the plants, the stimulating effect of bottom sediments on root growth was often indicated, while a toxic effect was demonstrated for T. platyurus in 80% of the samples. However, the correlation analysis and PCA results showed that trace elements that originated from similar sources were associated to the toxicity of sediments towards T. platyurus, while ecotoxicity for plants could not be explained by the content of trace elements in bottom sediments. T. platyurus is a good indicator for predicting the toxicity of bottom sediments from the Rożnów Reservoir. However, our study found that both chemical and ecotoxicological analyses are important for a comprehensive evaluation of the quality of bottom sediments.

The concentrations of polycyclic aromatic hydrocarbons (PAHs), their sources and toxic equivalent (TEQ) in soil, suspended matter and bottom sediments in the Fatala River Basin ecosystem were obtained for the first time to our knowledge. Determination of 14 PAHs (ΣPAHs) was carried out using high-performance liquid chromatography. The ΣPAH content in soil ranged from 13 to 50,920 (Me = 820) ng/g. The composition of PAHs (high proportion of low-molecular-weight compounds and values of individual PAHs ratios) reflected the significant oil pollution of soil. Contaminated soil was localated in the central part of the Fatala River Basin. The median benzo(a)pyrene toxic equivalent of soil at the study site was 1.08 (range, 0.05 to 53.16) ngTEQ/g, showing generally low soil toxicity. The ΣPAH content in suspended matter was in the range of 33 to 1316 (Me = 309) ng/L. The ΣPAH content in bottom sediments ranged from 36 to 6943 (Me = 478) ng/L, corresponding to clean and moderately contaminated sediments. The ΣPAH content in bottom sediments depended on the anthropogenic impact on the Fatala River Basin territory and the bottom sediment features. Bottom sediments and suspended matter had a low toxic equivalent.

In this study, we explore the fate of soils, from their erosion into rivers to their final deposition as either continental or marine deposits. We focus on the continental United States and compare the chemistries of river suspended and bottom sediment with the chemistry of the surface soils from which these particles originate. We find that river bottom sediment is closer to the chemical composition of soils than to suspended sediment, implying that a large fraction of surface soils end up as river bottom sediment. We identify Zr/Al as a robust tool to differentiate river suspended and bottom sediment, and we use this tool to calculate that in the rivers studied, ca 60% of weathered rock mass ends as river bottom sediments and ca 40% is transported as suspended load. The Zr/Al ratio of marine sediments is close to the ratio in river suspended sediments, and we calculate that marine sediments comprise greater than 90% river suspended material. Overall, through the pre-Anthropogenic Holocene, approximately 50% of the particles eroded from the soils of continental United States accumulate in continental deposits, with the rest being transported to the sea. The principles outlined here could prove useful in exploring the dynamics of soil transport to the sea in the geologic past.

PurposeThe use of bottom sediments in agriculture reduces the storage of excavated material and allows the nutrients it contains to be applied for soil fertilisation and improvement. However, the direct application of sediments to soil may cause numerous problems. Therefore, the addition of other waste materials may be a promising and useful method in the production of bottom-sediment-based growing media. The aim of the study was to evaluate the effect of growing media prepared on the basis of bottom sediments and various waste materials on the properties of soil as well as on the yield and chemical composition of courgette biomass.MethodsThe growing media were prepared with substrates in the form of mixtures with bottom sediments taken from the Rożnów reservoir. The effect of mixtures on plant growth was determined in a laboratory pot experiment. Air-dry mixtures (M1—bottom sediment with water treatment sludge (BS + SW); M2—bottom sediment with biomass ash (BS + BA); M3—bottom sediment with coffee hulls (BS + CH)) were mixed with soil (S) in the following proportions: combination I—25%, combination II—50%, combination III—75%, and combination IV—100% mixture.ResultsThe media did not have harmful effects on the plant or the soil environment. They had deacidifying properties; high contents of calcium, magnesium, potassium, and phosphorus; low total trace element content; and posed little risk of metal mobility. Heterocypris incongruens was the organism most sensitive to the substances contained in the studied media. The use of bottom-sediment-based media reduced the biomass of the test plant and, at the same time, limited the accumulation of trace elements in its aboveground parts.ConclusionMost of the analysed media were low-toxic to the test organisms and can potentially be used in agriculture, horticulture, or the reclamation of degraded land.

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.

The concentrations and composition of hydrocarbons (aliphatic, AHCs, and polycyclic aromatic, PAHs) are determined using molecular markers in bottom sediments of the Greenland–Norwegian basin and the Barents Sea (during the 84th cruise of the R/V Akademik Mstislav Keldysh in 2021). The research covered the deep-sea part of the Greenland Basin, the northern part of the East Greenland Ridge, the near-fault zone in the area of the junction of the Mohns and Knipovich ridges, the Western and Northwestern extremities of the Svalbard continental shelf (the Vestnes Ridge, the Ermak Plateau, the Sofia Basin, and the Hinlopen Trough), the Fram Strait, the Orly trough area with the intersection of the Erik-Eriksen trough, and the central part of the Barents Sea. The surface bottom sediments are found to contain a wide range of concentrations of C org (0.25%–2.71%), AHCs (7–182 μg/g), and PAHs (23–1918 ng/g). The distribution of HCs is determined by the processes occurring in the sedimentary stratum (changes in Eh and fluid flows), and, to a lesser extent, by the lithotype of sediments. Therefore, in the sedimentary stratum, autochthonous components form in the composition of alkanes and naphthalenes form in the composition of PAHs.

—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.

Major and trace element, PAH, and PCB concentrations were measured in surface sediments and particles from sediment traps collected in the First and Second Basin of the Mar Piccolo (Gulf of Taranto) in two periods (June–July and August–September, 2013). The aim of the study was to evaluate pollution degree, sediment transport and particle redistribution dynamic within the area. Results confirm the higher contamination of sediments from the First Basin observed by previous researches, particularly for Cu, Hg, Pb, total PAHs, and total PCBs. Advective transport from the First to the Second Basin appears to be the leading transfer mechanism of particles and adsorbed contaminants, as evidenced by measured fluxes and statistical analyses of contaminant concentrations in surficial sediments and particles from sediment traps. Long-range selective transports of PAHs and microbial anaerobic degradation processes for PCBs have been also observed. These results are limited to a restricted time window but are consistent with the presence of transport fluxes at the bottom of the water column. This mechanism deserves further investigation and monitoring activities, potentially being the main responsible of pollutant delivering to the less contaminated sectors of the Mar Piccolo.