5:15 PM - 7:15 PM
[MIS05-P16] Geochemical features of composition formation of lakes in the Western part of Valday Upland
Keywords:Valday Upland, speciation of elements, Visual MINTEQ, lake waters, environmental monitoring, background area
Environmental monitoring of hydrochemical characteristics of water bodies is an important task from a scientific point of view and in practice. Particularly important is the study of the territory of special protection. In the early 2000s, the problem of domestic and drinking water supply became urgent in the Valday municipal district. Accidents and wear-out failure of water supply networks and failures in the operation of treatment facilities, which created a direct risk to public health, were recorded. High colority and a significant amount of organic matter of humus origin, high bacterial contamination were established. Evaluation of the effectiveness of treatment facilities showed an extremely low degree of purification. Due to the lack of a biological stage of purification at the treatment facilities, polluted wastewater entered Lake Valday.
Two lakes were selected for monitoring: Gusinoe (glacial origin) and Valday (tectonic origin). There are settlements on the shores of Lake Valdayskoe. Lake Gusinoe is located 20 km west of the city of Valday, in the forest. Significant part of the lake shoreline is swampy. The main aim of investigation was evaluating of seasonal dynamics of the chemical composition and speciation of elements in lake waters.
Lake water samples were collected from March to October from 2017 to 2021. A total of 21 samples were collected. Samples were combined and analyzed in the laboratory. Measurement of pH, Eh, electrical conductivity, T °C were carried out in the field. The cation-anion composition was measured using an ion chromatograph Dionex ICS-6000EG. The microelement composition was determined by the ICP MS method.
The calculation of the speciation was carried out using the Visual MINTEQ computer program (version 4.0) and the built-in database of stability constants of metal complexes (Generic NICA-Donnan model). Average concentrations by seasons with fixed average values of pH, Eh, T°C, characteristic of the waters of the studied lakes for each season were used. The content of humic substances was estimated by the value of permanganate oxidability.
The highest phosphorus content in the waters of Lake Gusinoe is observed in summer, and in Lake Valdayskoe - in spring. It can be assumed that the lakes are eutrophic because of natural reasons - swamping and anthropogenic reasons - due to the diffuse load of coastal settlements. Calculations of speciation have shown that silicon is present in the waters in the form of orthosilicic acid, copper is characterized by the maximum degree of binding with humic substance. The maximum concentration of aluminum in Lake Valday in the summer season in the form of hydroxyl ion Al(OH)4- is due to the highest observed pH = 8.9. A decrease in pH provokes an increase in the proportion of organic aluminum complexes. Calculations showed that silicon is present in the waters in the form of orthosilicic acid, copper is characterized by the maximum degree of binding by humic substance. The maximum concentration of aluminum in Lake Valday in the summer season in the form of hydroxyl ion Al(OH)4- is due to the highest observed pH = 8.9. A decrease in pH provokes an increase in the proportion of organic complexes of aluminum. According to the data for the waters of Lake Gusinoe, the complete binding of aluminum by organic matter was calculated. The predominant part of the complexes is associated with the aluminum ion, and not the hydroxyl ion (2+), which is due to the slightly acidic pH. The main forms of Cu, Zn, Al in the studied lakes are their organic complexes. In spring and summer, organic complexes of Ni, Co with humic substances are dominant. According to the degree of binding with humic substance, the studied elements were ranked in the following rows for Lake Valday: Cu>Zn>Ni>Co>Al; for Lake Gusinoe: Cu>Al>Zn>Mn>Fe.
Two lakes were selected for monitoring: Gusinoe (glacial origin) and Valday (tectonic origin). There are settlements on the shores of Lake Valdayskoe. Lake Gusinoe is located 20 km west of the city of Valday, in the forest. Significant part of the lake shoreline is swampy. The main aim of investigation was evaluating of seasonal dynamics of the chemical composition and speciation of elements in lake waters.
Lake water samples were collected from March to October from 2017 to 2021. A total of 21 samples were collected. Samples were combined and analyzed in the laboratory. Measurement of pH, Eh, electrical conductivity, T °C were carried out in the field. The cation-anion composition was measured using an ion chromatograph Dionex ICS-6000EG. The microelement composition was determined by the ICP MS method.
The calculation of the speciation was carried out using the Visual MINTEQ computer program (version 4.0) and the built-in database of stability constants of metal complexes (Generic NICA-Donnan model). Average concentrations by seasons with fixed average values of pH, Eh, T°C, characteristic of the waters of the studied lakes for each season were used. The content of humic substances was estimated by the value of permanganate oxidability.
The highest phosphorus content in the waters of Lake Gusinoe is observed in summer, and in Lake Valdayskoe - in spring. It can be assumed that the lakes are eutrophic because of natural reasons - swamping and anthropogenic reasons - due to the diffuse load of coastal settlements. Calculations of speciation have shown that silicon is present in the waters in the form of orthosilicic acid, copper is characterized by the maximum degree of binding with humic substance. The maximum concentration of aluminum in Lake Valday in the summer season in the form of hydroxyl ion Al(OH)4- is due to the highest observed pH = 8.9. A decrease in pH provokes an increase in the proportion of organic aluminum complexes. Calculations showed that silicon is present in the waters in the form of orthosilicic acid, copper is characterized by the maximum degree of binding by humic substance. The maximum concentration of aluminum in Lake Valday in the summer season in the form of hydroxyl ion Al(OH)4- is due to the highest observed pH = 8.9. A decrease in pH provokes an increase in the proportion of organic complexes of aluminum. According to the data for the waters of Lake Gusinoe, the complete binding of aluminum by organic matter was calculated. The predominant part of the complexes is associated with the aluminum ion, and not the hydroxyl ion (2+), which is due to the slightly acidic pH. The main forms of Cu, Zn, Al in the studied lakes are their organic complexes. In spring and summer, organic complexes of Ni, Co with humic substances are dominant. According to the degree of binding with humic substance, the studied elements were ranked in the following rows for Lake Valday: Cu>Zn>Ni>Co>Al; for Lake Gusinoe: Cu>Al>Zn>Mn>Fe.