Numerical Modelling of Pollutant Dispersion in the Lower Danube River

This paper presents the numerical modeling results of the pollutant dispersion in the Danube riverbed, using experimental data recorded monthly on the Borcea-Bala-Old Danube sector, for a 2 years period. The water samples were collected from the left bank, center and right bank of the river, and the follwing indicators were analyzed: lead, nickel, chromium, cadmium and copper. Heavy metals were determined by atomic absorption spectrophotometry with graphite furnace (GFAAS). Numerical modeling was performed using Delft3D software, taking into account a reference situation (a scenario regarding the pollutant dispersion for known concentrations) and a scenario that simulates an accidental pollution (where the concentrations of pollutants were increased by 50 % compared to the values corresponding to Class V of water quality according to M.O. 161-2006). In order to properly assess the pollutant dispersion, the construction of the numerical model was developed taking into account a number of complex hydraulic works (bottom sill, dredging operations on the Danube in the area of confluence and downstream, on the whole width of the fairway). The results of numerical modeling generated the pollutant dispersion maps and the dispersion coefficients (indicating the transport of substances). Higher levels of the monitored indicators were observed on Borcea, caused by water coming from different sources of pollution (industry, agriculture, etc.) and discharged at a low flow, limiting the dilution.