Experimental and Model Studies of the Izhora River Waters Spreading in the Neva River

An experimental study of the distribution paths in the Neva River aquatic area one of the most polluted tributaries the Izhora River was carried out. Identification of tributary water in the Neva River was made based on the measurements of total dissolved solids values (TDS), as well as additional integral characteristic of water quality — redox potential (Eh). Based on the analysis of the results of the field experiment, it is shown that the waters of the tributaries (possibly polluted), after entering the Neva River, are pressed by the main stream to the shore and spread along it in the direction of the current. The effect of transverse turbulent diffusion, which contributes to the mixing of water masses, is insignificant. For the mathematical description of the mass transfer process in the Neva River, a conjugate mathematical model IL_MTRiver of the water flow, sediment transport and dissolved impurities in the open channel, developed at the на Institute of Limnology of the Russian Academy of Sciences, is used. The model implements an interconnected calculation of the variables of the state of the water flow and solid flow. A unified model allows to track the movement of water and suspended matter along the river channel and estimate the particles deposition rate. The interaction in the model of the moving stream and the river channel is represented by physically justified parameters — the coefficient of internal friction of the soil and the adhesion parameter of the soil particles in case of displacement. It is shown that the model adequately estimates the coastal distribution of impurities in the absence of mixing over the main flow cross section. In the future, the IL_MTRiver model can be used to solve the problems of assessing the possible pollution of Neva water in the area of urban water intakes and to predict the consequences of emergencies associated with the discharge of contaminated effluents at nearby enterprises, including the Krasny Bor toxic waste landfill.

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