Pulp and paper mills (PPMs) are one of the most water-intensive industries in the world. Where sulphite pulping is used to produce pulp for paper and other products, lignosulfonates (LSF) dominate the organic component of PPM wastewaters. Currently, there is no information about the quantitative composition of organic matter (OM) and contribution of LSF to the OM pool in lakes and rivers located within the zone of PPMs’ influence. Addressing this gap in our understanding, a method was developed for the characterization of allochthonous (humic substances, HS) and anthropogenic (LSF) components of OM, and labile organic substances. The method is based on the extraction of HS from a water sample with DEAE-cellulose, introducing an experimentally determined adjustment coefficient for partial LSF sorption. The method was applied to the second largest freshwater lake in Europe, Lake Onego (also known as Onega), and its Kondopoga Bay, receiving wastewaters of Kondopoga PPM. The method’s effectiveness was demonstrated through spatial segregation of the river and wastewaters in the bay in different seasons, first as a source of HS, and the second as a source of LSF. The vertical distribution of the river and wastewaters was indicated using conductivity, temperature, and TP. The proposed method demonstrated that HS in Kondopoga Bay make up on average 63% of the total OM pool and 17% of labile OM. However, LSF accounts for an average of 20% and up to 39% of the total OM pool, which confirms the high degree of anthropogenic impact on water quality of the bay.

Most of the plastic mass in the ocean is concentrated in coastal zones: large and small plastic items slowly circulate there for a long time, experiencing repeated episodes of beaching/recapture, fouling/defouling, sinking/resurfacing, aggregation, UV degradation, mechanical fragmentation, etc. In this chapter, physical and dynamical properties of marine microplastic particles (MPs, <5 mm) are summarized, with relevance to their behavior in the coastal zone. The density range, size classes, and typical particle shapes are presented, and their variation with time is considered. Results of laboratory experiments mimicking mechanical fragmentation of typical plastics in the swash zone are discussed and applied to oceanographically relevant cases. Relations between the mass and the number of generated MPs are experimentally obtained for four plastics typically found in marine environment. Dynamical behavior of MPs is discussed based on knowledge from classical hydrodynamics, marine sedimentology, and physical oceanography. Shape-dependent manner of the particle sinking and the value of the terminal settling velocity are considered, including the influence of vertical convection. Critical velocity of resuspension by a unidirectional flow is addressed, as well as motion of particles in an oscillatory flow under surface waves and in roll structures. Natural sorting of MPs at the shore face is highlighted, which suggests seaward export of smaller MPs, onshore transport of larger particles, and possible arresting of finer MPs below coarser sediment grains. The events of massive wash-outs of seaweed and plastics onto the beaches after severe storms are examined, and the potential of the machine learning methods in prediction of such events is highlighted. Importance of high surface waves, clastic shores, rocky headlands suggests that high-latitude coasts are effective generators of secondary MPs in the World Ocean.

The results of the diagnosis of the state and changes in the ecosystem of Onegskoe Lake (Lake Onego) and the watershed are presented using the developed information and analytical system “Lake Onego-watershed” (IAS), consisting of a comprehensive database (DB), a combined database of Roshydromet and Northern water problems institute/Karelian Research Center of the Russian Academy of Sciences on the nutrient load for the modern period 1995–2022, the ILLM mathematical model for assessing the removal of nutrients from the watershed and the formation of the nutrient load on the lake and the 3D-mathematical model SPLEM, developed for Lake Onego. Information was collected on the main sources of nutrient load in the Lake Onego catchment area, as well as available field observation data on the flow of nitrogen and phosphorus into the lake. The contribution of different nutrient sources coming from river runoff, diffuse sources, urban discharges and from trout farms was calculated for the lake and the main limnic areas. Based on data from field observations over the past 30 years and the results of numerical experiments using the SPLEM model with a grid resolution of 1 km it is shown that the ecosystem of the lake not only did not restored after the reduction in anthropogenic load after 1991, but eutrophication of waters in the lips and bays continues due to the influence of industrial and agricultural enterprises, trout farms and noticeable climate warming. Functional for the IAS “Lake Onego-catchment” to visualize the main modeling results on a 1 km grid was developed, and a web application interface has been created.

The article provides a review of GIS-based reconstructions of the development of Lakes Onego and Ladoga in the Late Pleistocene. It is shown that recently GIS methods have been used for reconstructions. At the moment, there are three GIS-based paleoreconstructions of the study area (Gorlach et al., 2017; Zobkov et al., 2019; Anisimov, Minina, 2020). All reconstruction used DEMs and digital bathymetry models of lakes. However, areas, volumes, maximum, and average depths for various stages of lake development are calculated only for Lake Onego (Zobkov et al., 2019; Paleolimnology…, 2022).

Data on the main sources of nutrient load on Lake Onego watershed were collected along with the available data of field observations of nitrogen and phosphorus inflow into the lake. Mathematical modeling was used to assess the agricultural load onto the lake and its possible decrease due to the introduction of the best available techniques to agricultural production. It was shown that a decrease in agricultural load after the introduction of best available technologies is unlikely to have a significant effect on the ecological conditions of Lake Onego. Simulation calculations were carried out to evaluate an increase in the input of N and P into the lake from fish farms on the watershed under the condition that the rate of fish farming growth in the water bodies in the basin will remain the same up to the year of 2050. It is shown that, in this case, an increase in nutrient load onto the lake by 3.9

The distribution of plastic pollution in the marine environment is highly variable in time and space, making it difficult to assess pollution levels. This study shows that mixing and natural sorting of material in the wave runup zone of a sandy beach results in a relatively stable abundance of microplastics in the size range 0.5-2 mm (SMPs). Based on 175 samples collected over 14 months during 42 monitoring surveys at 6 stations along the shore of the Vistula Spit (Baltic Sea), the mean abundance of S-MPs was found to be 64 +/- 36 items/kg DW (98.6 % fibers), with a coefficient of variation of only 56 % over more than one year. Statistical tests confirmed its independence from current wind speed, significant wave height, mean sediment grain size, sediment sorting, percentage of certain sand fractions, month, season, or location along the shore. It can therefore be used as a suitable indicator for long-term monitoring of increasing plastic pollution in the marine environment.

An interdisciplinary study of microplastic (MP) contamination in the water area of Lake Onego was conducted within a project funded by the Russian Science Foundation. The aim of the project was to assess the current state of this large water body, specifically its contamination with synthetic polymer particles and the associated heavy metals, to identify the sources and areas of MP accumulation, patternsin its sedimentation and transport, and to conduct a hazard assessment of this pollution. The article provides an overview and a summary of the obtained results. Based on seasonal hydrochemical data for 2019–2021, the current state of the lake was identified and the degree of its contamination with microplastics, heavy metals, and other chemicals was determined. The highest MP content was found in the water and in the bottom sediments of the upper, most heavily contaminated, part of the Kondopoga Bay, where wastewater from the Kondopoga Pulp and Paper Mill enters the lake. Active accumulation of MP was detected in the bottom sediments of Lake Onego, its content being about twice that of the Baltic Sea. Spatial and seasonal patterns of MP distribution in the water column of Lake Onego were revealed. It has been established that with the current level of Lake Onego littoral area contamination by irregularly shaped MP particles sized about 100 microns, their negative impact on the population of invasive species, Baikal amphipod Gmelinoides fasciatus, is unlikely. Having applied SEM-EMF and Raman spectroscopy, we revealed the mechanism for mineralogical destruction of plastics driven by the crystallization and growth of microminerals, which leads to local ruptures of the plastic and accelerates its destruction. Methods for fractionation of MP particles and desorption of metals from their surface have been developed, making it possible to obtain comparable and reproducible results when analyzing the metal content on their surface. For the first time, models were suggested to simulate microplastic generation from a set of macrofragments through stochastic destruction and filtering of three-dimensional microplastic fragments on a grid. The simulation results are in good agreement with the ratios obtained during field experiments.The revealed relationships can be used to adjust the detected levels of microplastics in the nature depending on the mesh size of the net used in sampling.

The concentrations of microplastic were determined in bottom sediments of water bodies in specially protected natural territories—Vodlozerskii National Park (Lake Vodlozero) and Kizhi Museum–Reserve (Kizhskie skerries, Lake Onega). The samples were taken at four stations in the Kizhskie skerries, Lake Onega, and at five stations in Lake Vodlozero. Microplastic (≥200 µm) was extracted from the samples by density separation. A random sample of particles was subject to chemical analysis with the use of micro-Fourier-spectrometry. Microplastic was found in all samples. In the Kizhskie skerries, the average concentration of the particles was 3413 ± 1965 pcs/kg dry weight of sediment, which is slightly higher than that determined before for Petrozavoskaya Bay and the open part of Lake Onega. According to chemical analysis, synthetic polymers account for 55

The sorption capacity of microplastic in respect of heavy metals (Co, Ni, Cu, Cd, Pb) in the natural water of Lake Onego was investigated. Microplastic particles of polyethylene terephthalate were obtained by grinding a plastic bottle aged in natural conditions. The type of polymer used to produce microplastics and the degree of its destruction were investigated using Scanning electron microscopy with energy dispersive X-ray spectroscopy, Raman spectroscopy and micro Fourier Transform infra-red Spectroscopy. The concentrations of metal additives in the model aqueous solutions for the construction of isotherms were close to those in Lake Onego and its tributaries. Obtained isotherms of metals sorption on the surface of microplastics in natural waters differed from those widely reported in the literature for model solutions based on distilled water. Conventional Langmuir and Freundlich models were able to describe sorption processes in Lake Onego water only within certain ranges of element concentrations, what is primarily due to the presence of natural organic matter and Fe and Mn hydroxides in the water of Lake Onego.

Data on the mineralogy and geochemistry of rare earth elements (REE + Y) in water, suspended matter and stratified sediment cores from different parts of Lake Onego are presented. The study finds that the dissolved REE + Y in the water from different areas of Lake Onego have common features: (1) a maximum in the area of middle rare earth elements (MREE), (2) a distinct negative Ce anomaly and (3) a positive Eu anomaly. Com- parison of the average concentration of elements in the stratified core of the bottom sediments and particulate matter (from the filters and sedimentation traps) from different parts of Lake Onego and the distribution of REE + Y do not reveal any significant differences. The trend of the REE + Y distribution for samples from the South Onego completely coincide the REE + Y distribution in siltstones and sandstones of the Russian Platform Scale Composite (RPSC). In the water area of Lake Onego from south to north, a well-defined trend of changes in REE + Y patterns relative to the RPSC is revealed, with depletion by heavy REE + Y and gradual enrichment by light rare earth elements (LREE). Geochemical and mineralogical data confirm our hypothesis of a significant reformatting of the catchment basin of the Onego Ice Lake in the Late Pleistocene. During the formation of the preglacial lake, a significant part of the catchment area was located south of Lake Onego and is mainly represented by Russian Platform sedi- mentary rocks. Due to the degradation of the Last Glacier from the Lake Onego depression and the nearby territories, the catchment area changed of its southern and south-eastern sections. Today the composition of the modern sedimentary matter entering Lake Onego is determined by mixing clusters from two geochemically contrasting feeding areas: loose sediments formed by the repeatedly re-deposited products of the weathering of the Fennoscandian Shield's crystalline rock massifs, including Phanerozoic sediments; and to a lesser extent the sediments of the sedimentary cover of the Russian Platform, except the bottom sediments of the South Onego, in which Phanerozoic sedimentary formations have completely predominated throughout the lake's development.

Определено содержание микропластика в донных осадках водных объектов особо охраняемых природных территорий – Водлозерского национального парка (оз. Водлозеро) и Музея-заповедника "Кижи" (Кижские шхеры Онежского озера). Пробы были отобраны на четырех станциях, расположенных в Кижских шхерах Онежского озера и пяти станциях на оз. Водлозеро. Экстракция микропластика (≥200 мкм) из проб проводилась путем плотностного разделения. Идентификация частиц проводилась при помощи бинокулярного микроскопа. Для случайной выборки частиц проведен анализ химического состава с помощью микро-Фурье-спектрометрии. Во всех пробах обнаружен микропластик. В Кижских шхерах среднее содержание частиц составило 3413 ± 1965 шт/кг сухого веса осадка, что несколько выше, чем ранее было определено для Петрозаводской губы и открытой части Онежского озера. По данным химического анализа, на синтетические полимеры приходится 55% частиц, 21% – представлены модифицированной целлюлозой, 24% – частицы природного происхождения. Максимальное содержание микропластика обнаружено рядом с главным пассажирским причалом музея-заповедника "Кижи". Среднее содержание частиц в донных осадках оз. Водлозеро было ниже, чем в Кижских шхерах, и составило 1506 ± 845 шт/кг, из которых 81% – синтетические полимеры, 9% – модифицированная целлюлоза, 10% – полимеры природного происхождения. Меньшее содержание частиц антропогенного происхождения в оз. Водлозеро по сравнению с Кижскими шхерами согласуется с показателями посещаемости этих природных территорий туристами.

Hydrochemical studies of the trout farming area in Kondopoga Bay of Lake Onego were carried out in the winter of 2022. Surveys at the deep-water site near the cages revealed dissolved oxygen starvation (0.8 mg/l) and a high content of ammonium (0.410 mg N/l) and mineral phosphorus (787 μg P/l, or 97 % of total phosphorus) in the near bottom level, which is comparable to wastewater from the Kondopoga pulp-and-paper mill. At other sites located in the trout farming area and at K50 located in the zone affected by Kondopoga PPM wastewater, which spreads over the bottom of the bay in winter, the dissolved oxygen content varied from 6.8 to 13.1 mg/l, the concentrations of NH4 + (up to 0.068 mg N/l) and Pmin (up to 51 μg P/l) were significantly lower than near the cages. Our data indicate the trout farms have a significant effect on the water chemical composition, confirmed by a previously detected long-term trend for an increase in TP content and intensive growth of phytoplankton in the central part of Kondopoga Bay.

The present dataset contains the chemical parameters of Lake Onego water. The data were obtained in different seasons covering the period 2019-2021. The concentration of Na+ and Cl− ions, the content of organic matter (TOC, CODMn, CODCr, water color, BOD5), nutrients (PO4-P, TP, NH4-N, NO2-N, NO3-N, TN), Fe, Mn, heavy metals (Cu, Ni, Cr, Zn, Cd, Pb), total suspended solids (TSS), conductivity, and pH of water were measured. The analyses were carried out by atomic absorption spectrometry, ICP-MS, spectrophotometric, spectrometric, gravimetric, flamephotometric, titrimetric methods, potentiometric, and conductometric determination. The data are useful for comparative analysis of the hydrochemical characteristics of Lake Onego and other large lakes, and they also allow to assess the water quality of the lake as a whole and in its particular individual areas.

An abundance of microplastics particles (0.2-5 mm, MPs) in bottom sediments is analyzed based on 53 samples (3 to 215 m deep) obtained in 8 cruises of research vessels across the Baltic Sea Proper in March-October 2015-2016. MPs content varied between stations from 103 up to 10,179 items kg-1 d.w., with the bulk mean of 863 ± 1371 items kg-1 d.w., showing a statistically significant increase with water depth. As many as 74.5% of MPs are of fibrous shape, followed by films (19.8%) and fragments (5.7%). The distributions of fibres, fragments, films, and different types of natural bottom sediments are significantly different, highlighting the specific behaviour of each of these kinds of bottom deposits. A statistically significant correlation between water depth and fibres content is found. Based on the analysis of oceanographic factors and sedimentological principles, an erosion/transition/accumulation pattern for fibres in the Baltic Sea Proper is outlined. Fibres can be considered as a specific type of "synthetic sediment", while principles of distribution of other MPs are not yet certain.

To indicate the potential role of Gmelinoides fasciatus, an invasive species of Lake Onego, in the inclusion of microplastics into food webs, several indicators were evaluated: its ability to ingest microplastics, the preferred size ranges, and the ingestion intensity. For this purpose, irregularly shaped polystyrene copolymer particles (acrylonitrile butadiene styrene plastics, artificially crushed) of four size classes (<50, 50-100, 100-250, >250 µm) were used. Gmelinoides fasciatus actively ingested microplastic particles, and in treatment with particles of 100-250 µm in size, the consumption rate was the highest. The crustaceans that survived the experiment ingested smaller particles than the deceased ones. Based on the size-frequency distributions of the ingested particles and the same in the suspension, crustaceans preferred smaller particles than those in suspension. The mean size of the ingested particles was 100 ± 5 µm. However, considering the actual concentration of microplastic fragments in the sediments of Lake Onego, in natural conditions, a negative effect of microplastic fragments on the G. fasciatus population is unlikely. At the same time, the ability of the invasive species G. fasciatus to consume microplastics and their active integration into the food webs of Lake Onego through consumption by fish can be considered reliable factors of the entry of microplastics in the fish of Lake Onego. Environ Toxicol Chem 2022;41:184-192. © 2021 SETAC.

Many publications have been devoted to the geological and geomorphological study of both Lake Ladoga and Lake Onega – the largest lakes of Northwest Russia and Europe. The last comprehensive geological studies of Lake Onega were carried out by Polar Marine Geosurvey Expedition as part of a geological survey at a scale of 1: 500,000 [12] and by Finnish researchers [19] at the beginning of the 21st century. Subsequently, these data were included in the third-generation State Geological Map at a scale of 1:1 000 000 [13]. Study of the basin’s geological structure was resumed in 2016 by researchers from the Northern Water Problems Institute of the Karelian Research Center of the Russian Academy of Sciences, St. Petersburg State University, Lomonosov Moscow State University and Herzen State Pedagogical University of Russia, as well as representatives of other scientific organizations. The works included geological sampling, drilling from ice platform, seismoacoustic profiling and side-scan sonar. The aim of the works was to clarify data on the structural features of the Upper Pleistocene and Holocene deposits of Lake Onega and the genesis of the lake basin relief. Based on the data obtained in the course of field studies, a new distribution scheme of the Lake Onega Quaternary deposits was drawn up. Comparison of the scheme with the data on the bottom topography made it possible to characterize its genesis and draw up a geomorphological scheme. The data presented in this article can be used to update and supplement the State Geological Map of the Northwest Russia, as well as to solve other problems of Quaternary geology and paleogeography.