Sedimentary processes in Lake Onego at the present time

N. A. Belkina; V. D. Strakhovenko; D. A. Subetto; N. A. Efremenko; M. S. Potakhin; N. V. Kulik; E. V. Gatalskaya; A. V. Ryabinkin; V. I. Kukharev; A. E. Rybalko; G. E. Zdorovennova; R. E. Zdorovennov; A. V. Ludikova

doi:10.31951/2658-3518-2022-A-4-1388

Sedimentary processes in Lake Onego at the present time

Authors: Belkina N.A.¹, Strakhovenko V.D.¹^,2, Subetto D.A.¹^,3, Efremenko N.A.¹, Potakhin M.S.¹, Kulik N.V.¹, Gatalskaya E.V.¹, Ryabinkin A.V.¹, Kukharev V.I.¹, Rybalko A.E.¹^,4, Zdorovennova G.E.¹, Zdorovennov R.E.¹, Ludikova A.V.⁵
Affiliations:
1. KRC RAS
2. V.S. Sobolev Institute of Geology and Mineralogy SB RAS
3. Herzen University
4. Arctic and Antarctic Research Institute
5. Institute of Limnology RAS
Issue: No 4 (2022)
Pages: 1388-1390
Section: Articles
URL: https://journals.rcsi.science/2658-3518/article/view/288514
DOI: https://doi.org/10.31951/2658-3518-2022-A-4-1388
ID: 288514

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Abstract

The data on studies of sedimentation processes in the Lake Onego were collected. The research program includes monitoring of atmospheric precipitation, the river flow, the distribution of suspended matter in the water column, the flow of suspended matter to the bottom and point source of pollution. The distribution and accumulation rates of sedimentary matter in the lake were determined. The composition of sedimentary matter has been studied.

Keywords

big lake, genesis of sediments, distribution of suspended matter, geochemical composition of sedimentary matter, accumulation rate

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1. Introduction

Lake Onego is the second largest Europe Lake. The catchment area (53,100 km²) and lake depression (9,720 km²) are located in the Northwest of the East European Platform on the border of the crystalline shield and the sedimentary plate (61°42´ N, 35°25´ E; 33 m a.s.l.). The northern part of the basin is composed of hard-to-dissolve crystalline rocks of the Archean-Proterozoic Fennoscandian shield, overlain by Quaternary deposits of small thickness (7-10 m). The southern part composed of rocks of the Upper Devonian and Lower Carboniferous. The crystalline rocks of the catchment area of Lake Onego are covered by a cover of Quaternary sediments (interglacial, continental, and marine formations of the Early, Middle, and Late Pleistocene).

Lake Onego basin has a well-developed hydrographic network including more than 6500 rivers and 9500 lakes (the lake-surface area density of 6.5%) (Litvinenko and Karpechko, 2015). The intensive destruction of Quaternary sediments is observed under the influence of denudation processes in a humid climate (Demidov, 2010; Subetto et al., 2020; Strakhovenko et al., 2018; 2020; Kulik et al., 2020a; 2020b; 2022; Belkina et al., 2008; Belkina and Kulik, 2018).

2. Materials and methods

Studies of sedimentation processes in Lake Onego include: (1) monitoring of atmospheric precipitation; (2) monitoring of river flow (10 large rivers, 4 seasons); (3) periodic observations of the distribution of suspended matter in the water column; (4) monitoring of the flow of suspended matter to the bottom (26 sedimentation traps (ST) are installed in different areas of the lake, the time exposition – 1 year (Fig.); (5) monitoring of the flow of solid material from point anthropogenic sources (official information). In order to perform task (4), a ST was constructed, a unique scheme for setting and lifting ST was developed, a method for sample preparation of suspensions from ST was developed, a method for selecting and separating suspended matter from natural water was modified.

Fig. Monitoring stations for studies sedimentation processes in Lake Onego

3. Results and discussion

The features of the distribution of suspended matter in the water column are established. Increased turbidity values are typical for shallow coastal areas of bays and at the confluence of rivers into the lake. Increased turbidity values throughout the water column were recorded in shallow small bays (Kizhi Skerries). In deeper bays (Gorskaya and Lizhemskaya Bays), turbidity increases with depth. Pronounced heterogeneity of turbidity distribution along the water column was revealed in the Kondopoga Bay. The reason for this is the spread of polluted waters of the Kondopoga Pulp and Paper Mill. In Petrozavodskay, Unitskaya and Povenetsky Bay, the connection of seasonal and interannual changes in turbidity to the development of phytoplankton was revealed. The deep-water central areas of the lake are characterized by maximum transparency, turbidity values increase with depth. In the southern part of Lake Onego, the interannual variability of turbidity is associated with wind effects on shallow water areas and river runoff.

Monitoring of the intake of the substance into the ST showed the uniformity of the granulometric composition and the uneven nature of the accumulation of sedimentary matter in Lake Onego. The amount of solid matter entering sedimentation traps during observations varied from 0.5 to 20 g year^-1. Very high quantitative indicators of the average annual intake of substances to the bottom were recorded in the peripheral areas of the open part of the lake (1600 g‧m^-2‧year-¹ in the North and 1100 g‧m^-2‧year-¹ in the South). In the Central part of the lake, it did not exceed 590 g‧m^-2‧year-¹. The maximum average annual intake of the substance in the bottom was recorded in the upper part of the Kondopoga Bay (more than 2 kg), but on average in the bay it was 1100 g‧m^-2‧year-¹ (the range of fluctuations in values in this bay is the widest). The minimum values of the average annual intake of substances to the bottom were recorded in the Povenetsky Bay (350 g‧m^-2‧year-¹, with fluctuations of 140 – 500 g‧m^-2‧year-¹) and at the outlet of the Gorskaya Bay (270 g‧m^-2‧year-¹, fluctuations of 160-370 g‧m^-2‧year-¹).

The rate of accumulation of suspended matter at the bottom, expressed in units of length (the thickness of the accumulated layer per year), varies by more than an order of magnitude for different stations: from 1 mm‧year^-1 (C4) to 3 mm‧year^-1 (K3) (on average 7 mm) of freshly deposited unconsolidated matter. Differences in the depths of the lake, as well as in the qualitative and quantitative composition of sedimentation material and differences in diagenetic transformations determine the different degree of compaction of the substance entering the bottom during the formation of bottom sediments. The lowest sedimentation rates were estimated for the deep-water areas of the lake: Bolshoe Onego, Povenetsky Bay and Lizhemskaya Bay. The highest rate of sedimentation is observed in the shallow upper part of the Kondopoga Bay, where bottom sediments are formed under the influence of wastewater from the Kondopoga Pulp and Paper Mill. The obtained values of the sedimentation rate for two stations (L18 and S3) were compared with the values of the sedimentation rate based on age dating by the distribution of isotopes ¹³⁷Cs and ²¹⁰Pb in the sediment column. The values were close: for L18 – 0.23 and 0.16 mm‧year^-1, for the southern part of the lake (S3) – 0.43 and 0.47 mm‧year^-1, respectively.

Chemical composition of the waters and the elemental, mineral and detrital particle composition of sedimentary matter in rivers and lake have been studied. The ratio of suspended and dissolved forms of elements varies depending on the area of the lake (the suspended form predominates mainly in Petrozavodsk and Kondopoga bay). The detrital matter in Lake Onego is represented by skeletons of diatoms, which are destroyed as they are deposited. The terrigenous component from ST and bottom sediments collected in different parts of the lake have a similar composition. It is represented by fragments of large and small grains of quartz, feldspar, muscovite, chlorite (which contain the ratio Fe≈Mg) and numerous small grains of accessory minerals. The suspended material of the sedimentation traps is similar in its external characteristics and physical properties to the surface (0-1 cm) bottom sediment in the areas of their installation on the lake bottom.

4. Conclusions

The basin of the Lake Onego has a complex structure, which affects the thermal regime and the dynamics of the waters, increases the heterogeneity of the ecosystem of the lake. As a result, there are local sedimentation basins with their own regime in the lake.

The sedimentary process in Lake Onego, controlled by water dynamics, involves the transformation of suspended matter in a complex biogeochemical way, resulting in the formation of new mineral phases of iron, manganese and silicon.

The rate of accumulation of suspended matter at the bottom varies by more than an order of magnitude for different areas of the lake.

Acknowledgments

The study was supported by the Russian Science Foundation grant #18-17-00176 (geochemistry and mineralogical composition of sedimentary matter), RFBR grant #19-05-50014 (diatom analysis), the state order «Study of the modern sedimentation regime of lakes in Karelia» of NWPI KRC RAS (development of monitoring program and expedition work).

Conflict of interest

Northern Water Problems Institute

Russian Federation, 50 Aleksander Nevsky str., Petrozavodsk, 185030

A. V. Ludikova

Institute of Limnology RAS

Email: bel110863@mail.ru
Russian Federation, 9 Sevastianova str., Saint-Petersburg, 196105

References

Belkina N.A., Ryzhakov A.V., Timakova T.M. 2008. The distribution and transformation of oil hydrocarbons in Onega Lake bottom sediments. Water Resources 35: 451-459.
Belkina N.A., Kulik N.V. 2018. The chemical composition of sediments as a criterion for assessing the state of lakes in the humid zone (on the example of the Karelian lakes). In: $3^{rd}$ International Conference “Paleolimnology of Northern Eurasia: experience, methodology, current status”, pp. 20-23.
Demidov I.N. 2010. Chetvertichnye otlozheniya [Quaternary deposits]. In: Filatov N.N. et al. (Eds.), Onezhskoe ozero. Atlas [Lake Onego. Atlas]. Petrozavodsk, pp. 29-30. (in Russian)
Kulik N.V., Efremenko N.A., Strakhovenko V.D. et. al. 2020a. Features of migration of Fe, Mn, Al, Cu and Zn in the Onego Lake. Limnology and Freshwater Biology 4 (SI:Paleo2020): 505-506. doi: 10.31951/2658-3518-2020-A-4-505
Kulik N.V., Belkina N.A., Efremenko N.A. 2020b. Introduction, transformation and distribution of manganese in lake Onego. Moscow Journal 1(13). doi: 10.24411/2413-046X-2020-10063 (In Russian)
Kulik N.V., Efremenko N.A., Belkina N.A. et al. 2022. Fe, Mn, Al, Cu, Zn, and Cr in the sedimentary matter of Lake Onego. Quaternary International. doi: 10.1016/j.quaint.2022.04.005
Litvinenko A.V., Karpechko V.A. 2015. Hydrographic characteristics of the reservoir and its basin. In: Filatov N.N., Kalinkina T.P., Kulikova A.V. et al. (Eds.), Krupneyshiye ozera - vodokhranilishcha Severo-Zapada yevropeyskoy territorii Rossii: sovremennoye sostoyaniye i izmeneniya ekosistem pri klimaticheskikh i antropogennykh vozdeystviyakh [The largest lakes-reservoirs of the North-West European part of Russia: current state and changes of ecosystems under climate variability and antropogenic impact]. Petrozavodsk, pp. 22-28. (In Russian)
Strakhovenko V., Subetto D., Hang T. et al. 2018. Mineral and geochemical composition of the Onega ice lake sediments. Baltica 31(2): 165-172. doi: 10.5200/baltica.2018.31.16
Strakhovenko V.D., Belkina N.A., Potakhin, M.S. et al. 2020. Mineralogy and geochemistry of suspended matter collected by sedimentary traps in different parts of Lake Onego (the first data). Limnology and Freshwater Biology 4: 507-508. doi: 10.31951/2658-3518-2020-A-4-507
Subetto D., Rybalko A., Strakhovenko V. et al. 2020. Structure of Late Pleistocene and Holocene Sediments in the Petrozavodsk Bay, Lake Onego (NW Russia). Minerals 10(11): 964. doi: 10.3390/min10110964

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2. Fig. Monitoring stations for studies sedimentation processes in Lake Onego

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