The contribution of primary production to the overall organic matter pool in Volga reservoirs

The results of studies of the concentrations and the ratios between the forms of organic matter in Volga reservoirs are presented. The reservoirs under consideration have different morphometric characteristics. flowage, and trophic status. Total organic matter content varies from 7.1 to 11.8 g/m³ or from 39.1 to 70.8 g/m² with the proportion of labile fraction of 4.4–15.2%. The primary production of plankton, the daily value of which accounts for 14–40% of labile organic matter, has a notable effect on its concentration and input. Organic matter pool in Volga reservoirs forms under the effect of the morphometric features of reservoirs, water exchange, and the drainage area. The total characteristics of organic matter in the Upper Volga reservoirs have not experienced significant changes over the 20-year period. However, data for 2005 show that the contribution of primary production to the total concentration of organic matter and its labile fraction have decreased due to a decline in the productivity of planktonic communities recorded in recent years.     

Organic Matter in the Waters of Lake Pleshcheevo Basin at the Present Stage

Organic matter concentration and parameters of its seasonal variations in the waters of the Pleshcheyevo Lake and the Trubezh River at the present stage during the operation of the lake water intake facility are presented. Results of comparison of these data with the ones obtained earlier testify to the capacity of the ecosystem to cope with various internal and external loads.     

Hydrochemical Characteristics of the Upper Volga Reservoirs in the Low-Water Season of 1997

The results of studies of the Ivankovo, Uglich, Rybinsk, and Gorkii reservoirs are analyzed. The studies involved a wide range of hydrochemical (salt composition, biogenic elements, organic matter, oil products, and heavy metals) and hydrophysical characteristics in the summer low-water period. The concentrations of organic matter and major biogenic elements are shown to decrease downstream along the chain of reservoirs with a respective general decrease in the trophic status. Large built-up areas located downstream of the Rybinsk Hydroelectric Plant are shown to adversely affect the river water quality.     

Concentration and localization of hydroxylamine in the reservoirs and lakes in the territory of European Russia

Hydroxylamine concentration and localization in the Volga reservoir cascade and in the lakes of Yaroslavl province and Vladimir province were studied. It was found that, in microaerophilic zones of the most productive lakes, the rate of hydroxylamine formation is higher and its localization does not depend on the type of the limnological object (a reservoir or a lake), but is determined by the oxygen regime of the water body in question.     

Forms, quantities, and variability of organic substance inflow into the Rybinsk Reservoir

The data on the content of total and some forms (suspended, labile, and carbohydrate-like) of organic substances in inflowing rivers of the Rybinsk Reservoir are presented. The greater portion of organic substances enters the Rybinsk Reservoir in the form of difficulty decomposable dissolved compounds. The labile fraction accounts for no more than 4.6% of the total amount. The distribution of the total organic substance runoff within a year correlates with the water runoff volume. The quantity of organic substance inflow with each river depends both on the water runoff volume and on the value of mean weighted concentrations of organic substances in water of these rivers. It is suggested that the obtained values should be considered as regional geochemical constants, which may be useful in preparing the total balance.     

Anthropogenic and Natural Components of Hydrocarbons in the Water of Lake Nero in Yaroslavl Oblast

The results of studies of spatial and seasonal variations in hydrocarbon concentrations in hypertrophic Lake Nero are used to discuss the problem of division of hydrocarbons into anthropogenic and natural components. It is shown that the use of bitumoids as a component of oil pollution instead of total organic matter can introduce errors in the results. Seasonal variations in the activity of hydrobionts in an undisturbed area are shown to have a notable effect on the assessment of the proportion of anthropogenic hydrocarbons in their total concentration, that is, on the assessment of the extent of pollution of water bodies. The natural component is found to dominate over the anthropogenic component only in the periods of algae blooming. In spring and autumn, the total concentration of hydrocarbons was found to exceed the MAC and to be due mostly to natural hydrobiological factors.     

Specific Features of Humic Substances Oxidation in Surface Waters in the Presence of Glucose

Experiments were conducted to study the microbial co-oxidation of naturally structured humic substances in different water bodies at different glucose concentrations. At low buffer capacity of aquatic ecosystems, the initial stages of the process are shown to be accompanied by a considerable increase in the medium acidity, a decrease in its alkalinity, and accumulation of colored intermediate products of bacterial and enzymatic synthesis. It is found that the co-metabolism processes with highly labile compounds either do not play any significant role in the trophodynamics of aquatic ecosystems (<10% of the original humic material is co-oxidized) or are not detected, notwithstanding the sufficient sensitivity of the analytical techniques involved. The low degree of co-oxidation (or its virtual absence) are found to be attributable to the masking effect of intermediate products.