The study on medium size river Sutla in Croatia indicated considerable water contamination at specific sites during the baseflow period, probably associated to low flow-rate (0.73-68.8 m3 s-1), and consequently low dilution capacity of this river. Various aspects of contamination were observed: increased conductivity to 1000 μS cm-1, decreased dissolved oxygen level to 50%, 4-5C increased water temperature, increased concentrations of several dissolved trace elements (e.g. maximal values of Li: 45.4 μg L-1 ; Rb: 10.4 μg L-1 ; Mo: 20.1 μg L-1 ; Cd: 0.31 μg L-1 ; Sn: 30.2 μg L-1 ; Sb: 11.8 μg L-1 ; Pb: 1.18 μg L-1 ; Ti: 1.03 μg L-1 ; Mn: 261.1 μg L-1 ; and Fe: 80.5 μg L-1) and macro elements (e.g. maximal values of Na: 107.5 mg L-1 ; and K: 17.3 mg L-1), as well as moderate or even critical fecal (E. coli: 4888 MPN/100 mL ; total coliforms: 45307 MPN/100 mL ; enterococci: 1303 MPN/100 mL) and organic pollution (heterotrophic bacteria: 94000 cfu/mL). Although metal concentrations still have not exceeded the limits considered as hazardous for aquatic life or eventually for human health, the observed prominent increases of both metal concentrations and bacterial counts in the river water should be considered as a warning and incentive to protect the small and medium size rivers from the future deterioration, as recommended by EU Water Framework Directive.
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