Geochemical Features of River Runoff and Their Effect on the State of the Aquatic Environment of Lake Onego

Self Cite

In 2009–2018, the isotopic composition of oxygen and hydrogen in the atmospheric precipitation, groundwater and river and lake water of Lake Onega basin was studied. The weighted annual isotope composition of precipitation at Petrozavodsk was δ18O = −11.7‰ and δ2H = −84‰ and varied from −30.9 to −4.1‰ for δ18O and from −23 to −22‰ for δ2H. The isotopic composition of the water in Lake Onega was relatively uniform from −11.5 to −9.3‰ for δ18O and from −85 to −71‰ for δ2H. In the bays, the isotopic composition of the water varied more substantially than in the central part of the lake due to the river runoff during springtime flooding. In late summer, the concentrations of deuterium and oxygen-18 increased in the lake water, and figurative points on the δ2H vs. δ18O diagram shifted above the meteoric line. The absorption of the isotopically heavy summer precipitation and disequilibrium isotope fractionation during evaporation led to the enrichment of the lake water by heavy isotopes. Experiments were conducted to estimate the evaporation influence on the isotope enrichment of the residual water, and a comparison of the obtained isotope data with the experimental function showed that commonly, about 4% and up to 12% of water was lost during the spring and summer, respectively. In the water of the tributaries, the abundance of the deuterium and oxygen-18 varied in a wider scale than in the lakes, from −14.4 to −9.1‰ for δ18O and from −102 to −73‰ for δ2H. An evaporation loss of up to 35% was found for the rivers in late summer, and this value was proportional to the area of lakes and wetlands in the elementary watershed. The initial isotope composition of the water in the tributaries prior to evaporation was estimated to be δ18O ≈ −14.1‰ and δ2H ≈ −103‰ on average and crossed the approximation and meteoric lines. This estimation was close to the average composition of the groundwater, i.e., δ18O ≈ −13.4‰ and δ2H ≈ −94‰ on the Lake Onega catchment. The slightly increased isotope depletion of the calculated composition in the initial river water in comparison with the groundwater was the result of the contribution of the spring snowmelt water, which had a significant influence on the lake water balance.

Section: Introductionmentioning

confidence: 99%

Isotope Composition of Natural Water in Lake Onega Basin

Borodulina

Tokarev

Yakovlev

2023

Self Cite

“…Precipitation is vital in the water cycle [24][25][26][27]. Affected by air masses that bring water vapor from different geographical regions, hydrogen and oxygen isotopes in precipitation reflect a combination of precipitation and recycling effects in the source area, providing the possibility of determining precipitation sources and quantifying the contribution of precipitation sources to runoff generation [28,29], as well as the dynamic processes of the watershed (such as evaporation, mixing of different sources) [30]. Numerous studies have shown that the distribution of precipitation isotopes depends on local temperature, latitude, altitude, and other climatic or geographical factors, which can be summarized as the following effects: seasonal, precipitation, temperature, continental, latitude, and sea level effects [11,[31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Hydrogen and Oxygen Isotope Composition in Precipitation, Rivers, and Lakes in Wuhan and the Ecological Environmental Effects of Lakes

Zhang,

Zhao,

et al. 2023

Wuhan has a dense network of rivers and lakes. Due to the city’s development, the water system has been fragmented, the degradation of lakes is becoming increasingly severe, and the eco-environment has been significantly damaged. By collecting samples of the central surface water bodies in Wuhan, including Yangtze River water, Han River water, lake water, and precipitation, and by utilizing hydrogen and oxygen isotopes and multivariate statistical methods, the hydraulic connectivity and ecological environmental effects between the Yangtze River, the Han River, and the lakes were revealed. The results indicated the following: (1) The local meteoric water Line (LMWL) in the Wuhan area was δD = 7.47δ18O + 1.77. The river water line equation was approximately parallel to the atmospheric precipitation line in the Wuhan area. The intercept and slope of the lake waterline equation were significantly smaller. The enrichment degree of δ18O and δD was Yangtze River < Hanjiang River < lake water. (2) The cluster analysis showed that the lakes could be divided into two types, i.e., inner-flow degraded (IFD) lakes and outer-flow ecological (OFE) lakes. Urban expansion has resulted in fragmentation of the IFD lakes, changing the connectivity between rivers and lakes and weakening the exchange of water bodies between the Yangtze River and lakes. Simultaneously, evaporation has caused hydrogen and oxygen isotope fractionation, resulting in the relative enrichment of isotopes. The IFD lakes included the Taizi Lake, Yehu Lake, and the Shenshan Lake. The OFE lakes and the Yangtze River were active, evaporation was weak, and the hydrogen and oxygen isotopes were relatively depleted, mainly including the Huangjia Lake, the East Lake, the Tangxun Lake, etc. (3) The excessive deuterium (d-excess) parameter values in the Yangtze River and the Han River water were positive. In contrast, the d values in the lakes were mainly negative. In the case of a weakened water cycle, the effect of evaporation enrichment on lake water δ18O and δD had a significant impact. It is suggested that the water system connection project of “North Taizi Lake-South Taizi Lake-Yangtze River” and the small lakes connecting to large lakes project of “Wild Lake-Shenshan Lake-Tangxun Lake” should be implemented in time to restore the water eco-environment.

Contemporary Sedimentation in Lake Onego: Geochemical Features of Water, Suspended Matter, and Accumulation Rate

Belkina

Kulik

Efremenko

et al. 2023

The spatio-temporal variability of the modern sedimentation process in Lake Onego, the second largest lake in Europe, was evaluated. The chemical composition of the lake water was studied. Sedimentation takes place in the oxidation conditions of low TDS water of the calcium bicarbonate type, where the ratio between terrigenous clastic material and lacustrine biochemical suspended matter in the material deposited to the bottom is close to one. We demonstrate that the sedimentation process in the lake is non-uniform. Sedimentation rates in different regions of the lake were estimated (0.1 to 2 kg per sq. m of bottom surface per year) through in situ surveys with sediment traps. Annual sediment input was estimated on the basis of the lake’s chemical balance. Analysis of the qualitative characteristics of the material deposited to the bottom shows its composition corresponds to the humus-Fe-Si type of sedimentation. The uniform texture and mineral composition and the similar multielement spectra of the sediments suggest that active water dynamics cause fine-grained suspended load to remain in the water column for prolonged time periods. Variations in the sediment chemical composition across the lake are due to natural causesand to unevenly distributed anthropogenic pressure.