This article is devoted to the study of water and sediment pollution in the channel of the Neva delta. Spectrophotometry was used to determine the concentration of pollutants in water. In the chemical analysis of the precipitate, atomic absorption spectroscopy and infrared spectroscopy were used. Analysis of the hydrochemical composition and sediment of the Smolenka River showed high concentrations of heavy metals and petroleum products. At the same time, the hydrochemical composition of the Smolenka River is highly unstable, but the concentration of oil products and lead in the sediments indicates the presence of local pollution sources. Based on our findings, we are guided by the restoration of the aquatic environment.

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The work is devoted to the topical issue of assessing the state and changes of river ecosystems located within the boundaries of large cities and industrial agglomerations. The paper presents the results obtained during hydrobiological studies on small rivers of St. Petersburg (Russian Federation) in 2019-2021. The application of bioindication methods is substantiated in order to assess long-term changes in aquatic ecosystems under conditions of increasing anthropogenic load. Various characteristics of the community of benthic invertebrates are used as biological indicators of the state of hydroecosystems. Benthos samples were taken on eight small watercourses of the city, which are both tributaries of the Neva River of various orders (the Okhta, Slavyanka, Chernaya Rechka, Lubya, Okkervil, Volkovka rivers) and delta watercourses (the Smolenka and Karpovka rivers). The paper provides a brief description of the studied water bodies and sampling sites. A number of biotic metrics and biotic indices used for bioindication purposes both in Russia and abroad have been identified. It is noted that the unstable hydrochemical regime and low flow velocity in the small watercourses of the Neva River delta contribute to the intensification of the accumulation of sediments with high concentrations of ecotoxicants, which negatively affects both quantitative and qualitative characteristics of biocenoses. In some watercourses re is a complete absence of bottom invertebrates, which can be assessed as an ecological disaster. When assessing water quality by quantitative and qualitative characteristics of communities of benthic invertebrates (Mayer index, BMWP index, some biotic metrics), it can be concluded that Okkervil River, Chernaya Rechka River and Volkovka River should be attributed to watercourses whose ecological state is extremely unfavorable. The ecological state of the rivers Karpovka River, Slavyanka River, as well as the estuaries of Okhta River and Smolenka River should be considered unfavorable. And finally, the situation in Lubya River, the source of Smolenka River and in the middle reaches of the Okhta River can be considered close to satisfactory (low quality according to BMWP or moderately polluted water according to IM).

Introduction. This article presents the results of studying the current environmental state of surface water bodies located in the affected area of phosphate mining enterprises and significantly altered as a result of technogenesis. Objects of accumulated environmental damage caused by mining enterprises contain the bulk (up to 85%) of waste accumulated in dumps, heaps and storages. In the Leningrad region, these are ash and slag dumps of the Slantsy Plant — about 35%, phosphogypsum of Fosforit Production Association and Volkhov Aluminum Smelter — about 18%, quartz sand with the content of phosphorite of Fosforit Production Association — about 17%, limestone — wastes from beneficiating oil shale of Leningradslanets Production Association — 12%, ash and slag dumps of CHPPs and state district power plants — 5%. In this regard, the authors assess the hydrochemical situation that has formed in the territory of the industrial site of ООО PG Fosforit in recent years. Methods. The article describes in detail a method for conducting field and laboratory studies for the period from 2017 to 2019, including a method for sampling and analysis. The authors analyze the content of basic anions and cations in a series of metals using high performance liquid chromatography and atomic absorption spectroscopy. Results. In the course of the studies, the authors revealed pollutants, the content of which in surface water bodies exceeds the maximum allowable concentrations. Conclusions. As a result of the studies, the authors identified sources of accumulated environmental damage and post-technological processes affecting the state of water bodies, and determined the trophicity of minor rivers in the affected area of decommissioned mining enterprises.