Spatial monitoring of heavy metals in the inland waters of Serbia: a multispecies approach based on commercial fish

The study monitored the contamination of fish muscle tissue by elements Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn at 17 sampling sites, in order to assess the pollution status of the main rivers in Serbia. Of the six commercially important fish species included in the study (pikeperch Sander lucioperca, catfish Silurus glanis, bream Abramis brama, barbel Barbus barbus, chub Squalius cephalus, nase Chondrostoma nasus), the bioconcentration factor (BCF) indicated that benthivore bream and barbel and predatory catfish have the highest tendency toward the accumulation of elements. This study achieved its primary objective and produced a contamination map of Serbia as a basis for further research. The estimated metal pollution index (MPI) showed the Tisa River to be unaffected by direct pollution (with an MPI value of 0.31) and the West Morava and Pek rivers to be affected (with MPI values of 1.92 and 0.73 for the WM₁ and WM₂ sampling sites and 0.65 for the Pek sampling site). Over the past two decades, Serbia has not expanded its industrial activity, which has resulted in the barely noticeable anthropogenic input of heavy metals in the rivers close to industry, and the main rivers are mostly unaffected and slightly affected. We assumed that pollution by heavy metals in the 1990s was trapped in the sediment, thus showing an increased concentration of elements in the species that live and feed on the bottom. Hg concentrations exceeded the maximum permitted concentrations (MPCs) only in catfish samples (0.62 mg kg⁻¹) from the Danube (D₃ sampling site) and barbel (0.78 mg kg⁻¹) from the West Morava (WM₁ sampling site), while Cd concentrations exceeded the MPC in catfish samples (0.09 mg kg⁻¹) from the Danube (D₁ sampling site) and chub samples (0.1 mg kg⁻¹) from the South Morava (SM₂ sampling site). The average concentrations of Pb exceeded the MPC in chub and barbel samples (0.32 and 0.82 mg kg⁻¹, respectively) from the West Morava (WM₁ sampling site); chub, barbel, and nase samples (0.35, 0.32, 0.31 mg kg⁻¹, respectively) from the West Morava (WM₂ sampling site); chub and barbel samples (0.35 and 0.3 mg kg⁻¹, respectively) from the Ibar; chub samples (0.39 mg kg⁻¹) from the Drina; chub and barbel samples (0.59 and 0.4 mg kg⁻¹, respectively) from the Great Timok; and nase samples (0.33 mg kg⁻¹) from the Pek. These results demonstrate that there is a need for future studies that would involve similar analyses and focus especially on smaller rivers that have been neglected so far.