This paper presents the first study of five small lakes located in the city of Murmansk. Field work was carried out during 2018–2019. Water samples were collected using a bathometer, while the sediments were sampled using an Ekman grab and Limnos gravity corer. It was found that the water of the studied lakes in Murmansk belong to the sodium group of the chloride class and to the calcium group of the hydrocarbonate class. Compared to the background level, elevated pH, concentrations of the main cations of alkali and alkaline-earth metals, N compounds, total dissolved solids, and heavy metals were found in the lakes, which indicate exposure to anthropogenic impacts. The sediments of the lakes, composed of organomineral and mineral silts, also have an elevated content of heavy metals compared to the background. The most significant excessive concentrations were found for V, Ni, Sb, Pb, Co, Cr, and W. Based on the calculated pollution load index and geoaccumulation index of the sediments, the studied water bodies in Murmansk can be classified as lakes with heavy and extremely heavy pollution levels. The primary pollution sources are emissions from the Murmansk thermal power plant, coal port, road and, rail transport.

The concentration of microplastic particles (with size from 100 µm to 5 mm) and their chemistry were studied in water, subsoils and sediments in the coastal area of the Neva Bay, the Gulf of Finland. The characteristics determined in the study were the dominating shapes of the particles, their size range, polymer chemistry and concentrations in different media, i.e., in water, bottom sediments, and coastal subsoils. Microplastic concentrations in bottom sediments and coastal subsoils are far in excess of their concentration in water mass. The spatial distribution of microplastic particles was studied in water, coastal subsoils, and bottom sediments of the Neva Bay, the Gulf of Finland. Microplastic concentration at the water edge was found to decrease with the distance from St. Petersburg City and Neva mouth, along either the northern or the southern coast. After reaching the Gulf of Finland, the Neva water, polluted by microplastic particles, is diluted and continues moving and distributing in accordance with the dominating westward hydrodynamic transport.

The chemical composition of sediments from the Arctic mountain Lake Bolshoy Vudjavr, situated in the western part of the Russian Arctic zone, was studied. The lake has been under intense anthropogenic load for more than 90 years since the development of the richest apatite–nepheline deposits in the world started. A 27 cm thick sediment core was sampled in the central part of the lake at the maximum depth of 37.4 m. The concentrations of more than 50 elements were analyzed by the mass spectral method, ICP-MS. The lake sedimentation rate established from the change in the content of the radioactive isotope ²¹⁰Pb was 2.3 mm/yr. The effluent from apatite–nepheline production and atmospheric fallout enrich the sediments of Lake Bolshoy Vudjavr with alkali and alkaline earth metals, N, P, Mn, Fe, Al compounds, rare earth elements, and trace elements (Sb, Cu, Zn, Pb, Bi, Nb, Ta, Th). Analysis of the forms of elements in the lake sediments showed that the studied elements are mainly found in stable fractions—mineral, acid-soluble, and associated with organic matter. The pollution of the sediments of Lake Bolshoy Vudjavr was assessed by the integral index PLI (Pollution Load Index) and CF (contamination factor). The PLI value sharply increased after the “Apatite” Plant had been launched and a large amount of wastewater from the mines had been released into the lake. The highest PLI values were detected in the sediment layers accumulated during the period 1990s–2000s. Sb (18.2), P (10.3), Sr (7.8), and La (6.0) have the maximum CF values among all the studied elements.

Humic substances are ubiquitous in terrestrial and aquatic ecosystems. Humic acids (HAs) actively interact with organic and inorganic components of lake sediments. This interaction depends on the molecular structure and elemental composition of HAs. The presented research focuses on the investigation of the composition and molecular structure of humic acids isolated from lakes located in the Lena Delta in the Russian Arctic. The findings of the research are needed to estimate the potential capacity of humic acids to bind microelements, particularly toxic metals, in stable compounds. Surface sediment samples (0–10 cm) were collected from 8 lakes by Van Veen grab during the summer period of the “Expedition LENA 2019”. We analyzed elemental composition of the HAs samples. The results showed that the studied HAs of lake sediments are characterized by low nitrogen content and prevalence of aliphatic fragments in their molecular structure. Furthermore, it was found that the studied humic acids are less mature, showing mineralization processes dominant over humification, and have relatively low potential to complexation compared with soils of the Lena Delta as well as lake sediments of territories with more boreal climate conditions.