Microplastic Abundance In Volga River: Results Of A Pilot Study In Summer 2020

In order to analyze the problem of microplastics pollution a comprehensive environmental survey was conducted along the entire Volga river in summer of 2020. The analysis of 34 water samples allowed us to determine the average concentration of microplastic (MP) in the surface water layer of the Volga river which accounted for 0.90 items/m3 (0.21 mg/m3). MP particles were found in all samples taken. The concentrations ranged from 0.16 to 4.10 items/m3 (from 0.04 mg/m3 to 1.29 mg/m3). The maximum MP concentrations were recorded in large cities downstream of the sewage treatment plants. For Tver, Nizhny Novgorod, Kazan and Volgograd they reached 3.77, 1.91,4.10 and 1.34 items/m3 respectively. The key role of large settlements as sources of MP in the Volga water was revealed. The minimum MP concentrations were recorded upstream of the large cities showing relatively stable levels of 0.25 items/m3 (0.05 mg/m3). The lowest MP content (0.16 items/m3) was revealed in the downstream area of the Cheboksary reservoir near Cheboksary. The results of weighing MP particles showed that their average concentration in the Volga water is 0.21 mg/m3. In each of the investigated samples particles of three determined fractions - fragments, fibers and films - were found, however, their ratio was not constant. On average, the proportion of fragments and films in the Volga water was 41% and 37% respectively and share of fibers accounted for 22%.

Composition, structure, and dynamics of phytoplankton in some left-bank tributaries of the Cheboksary Reservoir

The data on the composition, structure and dynamics of phytoplankton in morphologically different tributaries of the Cheboksary reservoir (the Vetluga, Kerzhenets and Vishnya rivers) are given. The floristic composition of algae includes 856 species and intraspecific taxa, algoflora is characterized as diatom-green-euglena algae. There is an increase in quantitative indicators of algocenosises from oligotrophic to oligotrophic-mesotrophic level in the middle course of the rivers, with mesotrophic-eutrophic level in the estuaries. The period of abnormally hot summer in 2010 led to increasing of vegetation of blue-green and dinophyte algae in the middle course and estuaries of the rivers. Since the early 2000s, penetration and naturalization of invasive algae species has been noted.

EVOLVEMENT AND DEVELOPMENT OF CHEBOKSARY HPP: TO THE HISTORIOGRAPHY OF THE ISSUE

The article presents an overview of research and social-political literature on evolvement and development of Cheboksary hydroelectric power plant. The authors carried out the analysis of scientific papers and publications using such scientific methods as system analysis, logical and structural research. The content of the article considers two periods in the historiography of the topic, each of which has its own peculiarities. The first period is mainly characterized by social-political literature. Publications are devoted to the grandeur of Cheboksary HPP construction. Particular attention is paid to the works, which were published by immediate participants of construction of the hydro-engineering complex. Historiography of this period mainly notes positive aspects of construction, negative aspects are either disregarded or considered insignificantly. The second period is characterized mainly by publications in periodicals. They are observed to contain more critical statements about the state of the hydroelectric power plant and Cheboksary reservoir. Articles about the difficulties in development of the hydro-engineering complex are analyzed. At this time studies of representatives of natural and technical sciences start to be published. They are devoted mainly to problems related to the rise of the water level in Cheboksary reservoir to the design mark. The analysis of publications on the ecological state of the flooding zone and hydrogeological survey of the hydro-engineering complex is also presented. The study makes it possible to state that the historical aspect of Cheboksary HPP evolvement and development in historiography has been studied extremely insufficiently. Most sources are marked by a departmental focus, journalistic character and a weak documentary base. The results of the review showed that there are no complex studies on the history of implementing the hydroelectric power plant construction in domestic historiography. The materials of the article can be used for further research of this topic, as well as when writing regional natural history works.