Peculiarities of mercury distribution,migration, and transformation in the estuarine area of the Northern Dvina River

The mercury concentration levels in the water of aquatic ecosystem of the Northern Dvina River delta are defined. The interrelations of mercury concentrations with physicochemical parameters of the water body, namely with pH, Eh, temperature, salinity, oxygen and organic matter content are studied. The dominant forms of mercury migration and its presence in the water are revealed. Regularities of changes and spatial variability of the mercury concentrations in the estuarine area of the river, peculiarities of mercury compound migration and transformation in the barrier zone of the Northern Dvina River-Dvina Bay of the White Sea are studied.     

Evapotranspiration in the basins of the Northern Dvina and the Western Dvina rivers and its variability

Considered is a possibility of using the previously developed method for estimating the evapotranspiration from the river basin based on the observations at the network of water- and soil-evaporation stations and on the data on the land use dynamics for the Northern Dvina and Western Dvina river catchments. It is demonstrated that the method enables to obtain rather realistic and reliable estimates both of evapotranspiration over the basin and of the contribution of different landscapes to its value. The value of evapotranspiration and its interannual variability depend not only on the trends in the fluctuations of evaporation from the water surface and the land surface, but also on the changes in landscape characteristics. The present paper is a continuation of the papers dealing with the study of the basins of the Volga and Don rivers started under V.S. Golubev’s leadership and participation.     

Anthropogenic load on the estuarine area of the Northern Dvina River

The results of calculation and analysis of the inflow of dissolved chemical substances to the estuarine area of the Northern Dvina River are considered. Based on the long-term regime hydrochemical information of the State Service of Observation and Monitoring of the Natural Environmental State, the anthropogenic load of dissolved chemical substances on the estuarine area and on the estuarine coastal water is estimated per inflow volumes. The extent of the water environment pollution of the near-delta part of the Northern Dvina River and its delta is estimated. The distribution of pollutant inflow among arms and channels in delta is under consideration.     

Polyvariant estimation of possible climatologic river runoff changes with emphasis on the Northern Dvina catchment

Rivers of the Northern Dvina catchment are considered to demonstrate the possibility of obtaining polyvariant estimates of changes in the water regime of rivers in the northern part of the forest zone, which are caused by expected changes in air temperature and precipitation. For this purpose, the dynamic-stochastic modeling approach was applied. The snowmelt and rainfall runoff model developed at the Hydrometeorological Research Center of the Russian Federation was used as a hydrological unit. Meteorological observational data collected during the 50- to 60-year period were statistically expanded by using an approach based on composing artificial variants of the annual cycle of meteorological variables, which can be performed through combining the observed variants of weather conditions of the cold and warm periods. As a result, polyvariant estimates of possible changes in the water regime of rivers corresponding to various scenarios of changes in air temperature and precipitation were obtained.     

Estimation of possible climatic changes of river runoff in the Northern Dvina River basin in the 21st century

Presented is a method of studying possible climate-driven changes of river runoff characteristics, according to which the atmosphere-ocean general circulation models are used for computing the climate system impact, whereas the response of a watershed to given disturbance is estimated using the model of runoff formation in a river basin. The study is carried out for the Northern Dvina River basin. Estimates of possible changes (relative to the reference period) by the middle and late 21st century of such water regime characteristics as mean annual and maximum water discharge, as well as mean discharge values for the spring, summer-fall and winter seasons, are presented.     

Geochemical aspects of accumulation of macroelements in the subcolloidal fraction of bottom sediments at the Razdol’naya River-Amur Bay cross-section (the Sea of Japan)

The concentration of Si, Al, Mg, K, Ca, Na, Sr, and Ba in the subcolloidal fraction of sediments at the Razdol’naya River-Amur Bay cross-section is determined using the atomic emission spectroscopy method. Computed is the mean content of studied elements in the soil and river bottom sediments (to the mixing zone). Revealed are river bottom sediments with the high concentration of macroelements corresponding to the zone of mixing of fresh river water and salt sea water. It is demonstrated that the additional accumulation of macroelements (Ca, Na, and Sr) in these sediments is associated with the formation of hydroxides of Fe and Mn and processes of sorption (Mg, Ca, Na, K, Sr, and Ba) on clay minerals (hydromica and smectites).     

Monitoring of polycyclic aromatic hydrocarbons in the Lake Baikal basin in the areas of intensive anthropogenic impact

Presented are the results of studying the content of polycyclic aromatic hydrocarbons and benz(a)pyrene in the lake water, in sewage waters of the enterprise, and in the upper 2-cm layer of bottom sediments in the area of the sewage discharge of Baikal Pulp and Paper Mill (BPPM), in bottom sediments in the north of Lake Baikal in the area of the Baikal-Amur Railroad, and in the channel and delta front of the Selenga River. The results were obtained at Hydrochemical Institute in 1981?C1989. The different content of benz[a]pyrene was determined for the first time in bottom sediments (sands and silts) for the bottom area of polygons in the mentioned regions. An intensive pollution exceeding significantly the normalized parameters for the benz[a]pyrene in bottom sediments is registered in the BPPM area only and its content in other areas does not exceed the background values on the whole.     

Influence of intrareservoir and meteorological factors on the rate of oxygen demand by valley reservoir sediments

Analyzed are the spatial and temporal variations of the sediment oxygen demand rate in the Mozhaisk Reservoir. It is demonstrated that this rate in summer depends both on the sediment characteristics and on the biological and meteorological factors. It is revealed that the content of labile organic substances in the silt is of great importance for the oxygen consumption rate (all other factors being equal). The inflow of these substances to the bottom is regulated by the water column stratification depending considerably on weather conditions. Estimated is the contribution of main organic matter consumers in the bottom sediments.     

Arsenic content in water and bottom sediments in the areas of chemical weapon dumps in the Bornholm basin of the Baltic Sea

Data are considered on samples taken during the 2006–2008 expeditions from the water and bottom sediments in the areas where chemical weapon was dumped in the Bornholm basin. Arsenic concentration is detected with the X-ray fluorescence analysis and inversion voltammetry. Results are under consideration of the enhanced arsenic content and their relation to arsenic-bearing toxic agents. It is pointed out that arsenic contamination is local in character and at present is of no serious hazard to the natural environment.     

Assessment of water quality in the rivers of northern European Russia by using oxygen demand indices

Analysis of the probability curves of multiyear organic content data and water colour indices of the rivers located in the northern part of European Russia (the Northern Dvina, Pechora, Onega, and Mezen) allowed revealing seasonal patterns of hydrochemical indices. Water quality for different seasons was assessed. Regional estimates of hydrochemical indices and water quality were obtained. Relations between oxygen demand indices, water colour indices, and water content of those rivers were considered.     

Forecasting environmental contamination development in the coastal and water area of the Russian far east under the effect of the radiation factor and industrial anthropogenic load under conditions of catastrophes

Studies of seasonal variability (including the winter season) of the main hydrodynamic, sedimentation, physicochemical and other characteristics of the Chazhma Bay of the Sea of Japan, in the zone of the atomic submarine K-431 nuclear accident of 1985 that influence the radioecological state of the environment was carried out. The substance fluxes required for estimating radionuclide balance are defined based on the expedition survey of radioactivity of bottom sediments, sea water, and suspension in the epicenter of the accident and over the water area of the bay together with hydrophysical, sedimentation, and meteorological observations. Modern trace methods and 3D prognostic modeling of interaction of natural and anthropogenic processes of evolution of radioactive contamination of the bottom sediments in the zone of the atomic submarine accident are used; a new approach to estimating the maximum contamination of the marine environment is proposed.     

Winter severity effects on the nonuniformity of winter flow formation in a river basin

Results of studying winter flow formation in the Northern Dvina and Lovat?? river basins are presented. Substantial effect of temperature factor on water exchange between upper and lower parts of a river basin is established.     

Methane emission at the main stages of technological cycle of sewage waste water purification at Rostov-on-Don aeration station

The methane concentration in the waste water coming to the aeration station is 1130 μl/l on average and it decreases to 11 μl/l after all purification stages. Experimentally measured methane fluxes to the atmosphere from the waste water under purification and sewage sediments of silt fields varied within 0.2–50.1 and 98.3–188.8 mg/m² per hour, respectively, and correlated closely enough with the gas content in them. An approximate total methane emission by the purification plants is about 475 kg per day and the major contribution (83%) belongs to the silt field sediments characterized by its extremely high content (42.42–199.49 μg/g of the damp sediment). It is demonstrated that the regression equations obtained by the authors before and approximating the relation of the methane content in the water and bottom deposits of water bodies with its fluxes to the atmosphere can be used to estimate the methane amount emitted during the waste water purification.     

Studying the influence of cyclonic activity on suspension distribution in the sea water of the northwestern Black Sea

Processes of roiling, transport-diffusion, and deposition of fine disperse bottom sediments are studied in the northwestern shelf of the Black Sea in different synoptic situations connected with the passage of cyclones. Movement of atmospheric disturbances with velocities of 5 and 15 m/s along three trajectories typical of this region is considered. A nonlinear sigma-coordinate numerical model is used to calculate hydrodynamic and suspension concentration fields. The bottom areas, most sensitive to erosion, and the areas of maximum accumulation of depositions due to their sedimentation are determined. The change in suspension distribution in the surface layer with time is studied.     

Present-day characteristics and trends of long-term changes in ecological and toxicological conditions of the Tsimlyansk Reservoir

The analysis of ecological and toxicological conditions of the Tsimlyansk Reservoir and of trends of long-term variations of hydrochemical, hydrobiological, and biotesting parameters is carried out on the basis of long-term data of Roshydromet regular observations (1984?C1991) and authors?? studies (1990, 2006?C2007). It is revealed that, according to the complex of chemical parameters, the water pollution level decreased by the end of the period and is relatively low at present, although the pollution is of stable nature and the toxic and carcinogenic compounds are discovered in the water and in bottom sediments. The most dangerous display of the reservoir eutrophication is a ??bloom?? of algae characterized by the prevalence of blue-green algae (Cyanophyta) amounting to 100% of the total biomass in some samples; the species being able to discharge the toxins to the water (Aphanisomenon flos-aquae, Microcystis aeruginosa, Anabaena flos-aquae) often prevail. During biotesting, the samples of water and bottom sediments in a number of cases exerted a toxic effect on the water organisms and, most likely, the toxicity increases with time. Although different parts of the reservoir differ considerably in ecological and toxicological parameters, an ecologically unfavorable situation emerged in the reservoir ecosystem due to the pollution, eutrophication, and toxicophication.     

Computing the methane cycle elements in the aquatic ecosystems of the Sea of Azov and the World Ocean based on empirical formulae

Empirical relationships between methane concentration and the rates of its oxidation and emission in the sediment-water-atmosphere system are computed using the experimental data and the data presented in the literature. For the Sea of Azov and the World Ocean the possibility is demonstrated of using the empirically derived formulae to compute the methane cycle elements in aquatic ecosystems. The comparability of methane volumes in the water column and bottom sediments as well as of those oxidized and released from water and sediments computed using these formulae, demonstrates the adequacy of the obtained formulae. It is shown that depending on morphological parameters of reservoirs of aquatic ecosystems and on their volume and area, the ratio of the amounts of methane that is oxidized and released to the atmosphere, changes as well as the rate of its turnover.     

Dynamics of accumulation of heavy metals by subcolloidal fraction of bottom sediments is a result of biochemical processes in the marginal filter of the Razdol’naya River (the Amur Bay, the Sea of Japan)

Determined is the content of Fe, Mn, V, Cr, Cu, Zn, Pb, As, and Sc in the subcolloidal fraction of sediments of the Razdol’naya River marginal filter using the method of atomic emission spectroscopy. Proposed is one of the variants of separating biochemical zones with the increased content of Fe and Mn and other metals in the bottom sediments of the marginal filter: the river zone, the zone of flocculation and formation of Fe and Mn hydroxides, and the zone of biochemical metal accumulation (marine). In the sediments of the river zone and the zone of flocculation and formation of Fe and Mn hydroxides, two bottom areas are identified with the high content of the elements under study that is associated with long-term and seasonal variations of the river runoff.     

Freezing types and winter runoff of small rivers

Investigations carried out in the Northern Dvina River basin revealed that the decrease in the ice thickness on small rivers is of significant importance in the increase in the water content of rivers in winter in recent decades. This process resulted in the improvement of the channel capacity as a result of the decrease in the ice formation intensity on the rivers and of the increase in the fraction of ground waters participating in the winter river runoff formation. It is proposed to consider the initial winter ice conditions as a separate important factor of this process as they define the types of river freezing influencing on the winter river runoff formation as well.     

Peculiarities of distribution and accumulation of heavy metals in anthropogenic silts of the Pakhra River basin

The bottom sediments of minor rivers undergo the considerable changes in industrial urbanized and agricultural regions. They differ from the river alluvium in the content and form of chemical elements that is caused by the specificity of enterprises located on the territory adjoining the rivers.     

Formation factors and forecast of ice dams on rivers of the north of the European territory of Russia

Regional peculiarities of ice dams’ formation process on large rivers of the north of the European territory of Russia are considered. Methodology and methods of ice-clogging floods’ forecasting at stretches with the risk of ice dams of the Northern Dvina, Sukhona, Vaga, Pechora, and Mezen’ rivers are described. Method of forecasting of the flood characteristic, which has not been forecasted before at ice dams, the duration of high water levels’ stand, is proposed. The possibility to plan ice-dam prevention activities on the base of hydrological forecasting is shown.