Role of hydraulic parameters in the concentration and spatial distribution of heavy metals in sediments in a two-stage reservoir

The role of hydraulic parameters in sediment transport and heavy metals concentration still needs scientific research. In this study, GIS techniques, IBER (a 2D hydrodynamic modeling system) and statistical analysis were applied to assess heavy metals concentration, spatial distribution and sources. A total number of 30 surface sediment samples were collected from the Stare Miasto two-stage reservoir. Results showed that median values follow order Zn > Pb > Cu > Cr > Ni > Cd, which was characteristic for both parts of the reservoir. The overall calculated median concentrations of Zn, Pb, Cu, Cr, Ni, and Cd were 6.74, 1.66, 1.14, 0.99, 0.8, and 0.04 mg/kg. Analysis of heavy metals concentration shows that higher mean values were observed in the pre-dam part for all of the analyzed heavy metals. The highest risk was observed for Zn, Pb and Cd for all of the analyzed samples. Statistical analysis showed that heavy metals concentration is correlated with the fraction of sediments and distance from the inflow. Spearman’s rank correlation showed that hydraulic parameters affect heavy metals concentration. Critical diameter was negatively correlated with Cu while Froude number and velocity were negatively correlated with Cu and Zn concentrations. Also, it was observed that Cu concentrations in the main zone were positively correlated with specific discharge. Results showed that the two-stage construction of the reservoir has an impact on the limitation of sediments spatial distribution and helps to control pollution related to heavy metals.