engleski

Assessment of heavy metals contamination in water and biota of the Mrežnica River

Once present in aquatic environment, metals may remain dissolved in the water as free ions, complexes and colloids, or adsorbed by suspended particulate matter, both of which serve as pathways of uptake into benthic animals. In many freshwaters, bivalves have a key role as filter- feeding, sediment-dwelling animals. The lower course of the Mrežnica River has been long exposed to various types of industrial loads which may adversely affect them. To assess the metal contamination of the Mrežnica River affected by anthropogenic influences, the concentrations of five non-essential elements (Ag, Cd, Cs, Pb and Tl) were measured in dissolved and particulate phases in the water and in the digestive gland of Unio crassus mussels at two sampling sites (the industrial area of Karlovac as a polluted site and a location upstream from the Town of Duga Resa as the reference site) in spring 2021. Water samples were filtered through a 0.45 μm pore diameter filter. The water filtrates containing dissolved metals were acidified with nitric acid, while the suspended material remaining on the filter was dried and then digested with nitric acid. Tissue samples were digested with mixture of nitric acid and hydrogen peroxide. The metal concentrations were measured using a high resolution inductively coupled plasma mass spectrometer. In dissolved and/or particulate phase in water, elevated Cs and Tl concentrations were detected at Karlovac, while Cd was higher at the reference site. Increased concentrations of these metals coincided with increased concentrations in U. crassus specimens. Although higher concentrations of Ag and Pb in the particulate phase were also detected at Karlovac, expected changes in the bioaccumulation of those metals were not observed in the digestive glands of U. crassus. Trend of higher concentrations of highly toxic metals at the Karlovac industrial zone indicated a potential risk for the Mrežnica River ecosystem. Thus, further monitoring of both water and biota is recommendable.

Heavy metals ; Contamination ; Water ; Biota ; Unionidae ; Particulate ; Dissolved

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