The Novgorod region is rich in rivers and lakes. First of all, this is due to the relief, the depth of groundwater and the climate. From the annual amount of precipitation evaporates 325-375 mm. The rest of the moisture feeds rivers, lakes and marshes.
Lakes of the Novgorod region are poorly studied, some do not even have names. They, like rivers, are distributed unevenly across the territory of the region. Lakes in the eastern part of the region are larger than in the western part. This feature of the location of lakes is associated with the origin of the lake basins. In the eastern, elevated part of many small and medium-sized lakes of glacial origin, having an oval or lobate shape. The largest glacial lakes of the region are Velikoye, Meglino, Velye, Borovno, Zaozerye. The largest lakes, the Ilmen and the Valdai, occupy depressions that were formed in preglacial times and then processed by a glacier. In the east of the region there are karst lakes. These include Lake Gorodno, Yamnoe, Sukhoi in Borovichi and Khvoyninsky districts. In years with dry summers, the basins of some karst lakes may dry up (Lake Gorodno and others). But in addition to them, there are more than 1,500 small lakes in the Novgorod region, which, at times, are not even registered in the cadastre of water bodies and have no official name. Often such lakes are within the boundaries of rural settlements and other settlements. This group includes the Borovenkovsky and Beloye lakes.
Lake Beloe is located one and a half kilometers from the village of Borovenko and has been used for many decades by the local population for bathing and fishing. The lake is stretched from west to east. Its length is 1.75 km, average width — 201 m. The surrounding area is hilly, covered with coniferous forest, the hillsides are steep, the peaks are flat, flattened. The bottom is sandy.
Lake Borovenkovskoe is located on the territory of the village of Borovenka and is one of the main recreational facilities of this settlement, as well as a place for watering animals in the summer. The lake is stretched from west to east. Its length is 715 m, the average width is 80 m. The banks are covered with grass, in some places coniferous trees; Bottom — sand and silt. In the east the lake gives rise to the Borovenka River, which in turn flows into the Horinku River.
On the territory of a rural settlement there are 3 timber processing enterprises. Some of the local residents are engaged in farming in their household plots.
The administration of the settlement monitors the state of the coastal zone of the lakes. For this purpose, subbotniks are organized, in which the local population, in particular schoolchildren, participates. Also near the beaches are garbage bags, which are regularly exported.
The aim of the work was to assess the water quality of the Beloye and Borovenkovsky lakes in terms of hydrochemical and sanitary-microbiological indicators. For this purpose the following tasks were set:
— conduct a chemical analysis of water;
— to conduct a sanitary and microbiological analysis of water;
— determine the trophic status of water bodies.
Laboratory studies were carried out with the participation of the research laboratory of the enterprise LLC «Corporation Seven Ruches» in Okulovka.
Sampling for sanitary-microbiological and hydrochemical studies was carried out using the generally accepted methods of GOST 31861-2012 «Water. General requirements for sampling «, GOST 31942-2012» Water. Sampling for microbiological analysis «.
In the hydrochemical analysis of the waters of the Beloe and Borovenkovsky lakes, the following results were obtained (in fractions of the MPC): turbidity 0.6-0.8; Chromaticity 0.46-, 62; PH 0.9; Chlorides 0.008-0.01; Iron 0,4; Sulfates 0.002-0.004; Permanganate oxidation 0.7-0.8; Hydrogen carbonates 0.33-0.61; Alkalinity 0.33-0.6; Nitrites 0.01-0.1; Nitrates 0,006-0,008.
Trophic status is a characteristic of a reservoir in terms of its biological productivity, which is estimated by the value of primary production. There are 4 main types of water bodies: oligotrophic, mesotrophic, eutrophic, dystrophic. For the assessment of the trophic status of natural waters, indicators such as primary production, chlorophyll a concentration, phytoplankton biomass, etc. are traditionally used. All of them require special studies and are rarely determined in the usual practice of ecological monitoring of water bodies. In connection with this, the importance of other, indirect indicators of the trophic state of the ecosystem (especially its temporal variability) increases, for which there is a sufficient number of observations. In particular, an increase in the trophicity of the ecosystem can also be indicated by an increase in the background of the amount of organic substances (including those easily oxidized, estimated by the permanganate oxidation capacity), an increase or a violation of their vertical distribution and seasonal course. Permanganate oxidability is a widely used hydrochemical index, the determination of which, as a rule, is carried out with many hydroecological observations. An analysis of the permanganate oxidizability in the water bodies examined showed that the water’s oxidizability is comparatively small.
Discharge of organic, bacterial and chemical pollutants into reservoirs can result from exceeding the ecologically permissible load on the reservoir, which in turn will lead to a violation of sustainability and the destruction of the ecosystem. A large role here is played by the capacity of the medium, thanks to which the ecosystem of the reservoir remains stable when pollutants enter. The capacity of the reservoir for self-cleaning has boundaries. In small and non-permanent water bodies, self-cleaning capacity is extremely low. If we consider together with this the use of a reservoir for domestic, drinking or cultural and household purposes, then, ultimately, this can lead to negative consequences for human health.
The number of saprophytic bacteria is closely related to the amount of organic matter that can be easily assimilated by them from water, and is an indicator of the trophicity of the reservoir. The total number of bacteria at the time of the studies in both lakes did not exceed 1.5 million. L / ml. In the lake. Borovenkovsky average number of bacterioplankton averaged 0.97 mln.kl / ml, and in White — 0.86 mln.kl / ml. In connection with this, it is possible to classify these lakes as mesotrophic. Also, based on these values, the saprobity coefficient can be calculated. For Lake Borovenkovskogo, it was 0.07, for the White — 0.05, which indicates the purity of the water of these lakes.
The number of coliform bacteria is an indicator of fecal contamination of the reservoir. When studying the Borovenkovsky and White lakes, coliforme and thermotolerant bacteria were not detected. According to this indicator, the water of this reservoir refers to uncontaminated waters.
Summarizing the obtained data, it can be noted that for all indicators, water bodies are suitable for recreational purposes, as well as for domestic and fishery activities. According to hydrochemical and sanitary-microbiological indicators, water bodies correspond to pure waters — grade I of purity.
Based on the work done, it can be recommended to continue monitoring water reservoirs.
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Ecology of microorganisms: Textbook for students. Universities / A. I. Netrusov, EA Bonch-Osmolovskaya, VM Gorlenko and others; Ed. AI Netrusova. - Moscow: ed. Center "Academy", 2004. - 272 p.