engleski

Characterization of the water and sediment quality of the lower course of the Mrežnica River: the effect of long-term historical contamination

The lower course of the Mrežnica River has long been exposed to different types of industrial loads. In Duga Resa, the cotton industry was active for more than a century, and a few kilometres downstream, industrial wastewaters of Karlovac entered the river until approximately a decade ago. Our aim was to determine the main inorganic and organic contaminants of river-water and sediments at two differently polluted sites compared to upstream reference site. Turbidity, chemical oxygen demand, and total nitrogen were somewhat increased in Karlovac, whereas total phosphorus was increased at the reference site. Although dissolved metal concentrations in the water were rather low, indicating a pristine river, an increasing trend towards Karlovac existed for several elements (e.g., Fe, Mn), where the highest metal concentrations in finer sediment fraction (<2 mm) were also observed. The highest portion of finer fraction in total sediment observed in Duga Resa (100%) compared to the other sites (reference 13%, Karlovac 54%) probably lead to higher metal bioavailability at both industry impacted sites compared to the reference site. The screening of 626 organic compounds in the river- water revealed ten-fold higher total concentration in Karlovac compared to the other sites, and their types varied by sampling site. Herbicides used in agriculture (atrazine) were detected upstream, whereas herbicides applied in water-tanks (neburon) were found in Karlovac. The results indicated mild agricultural impact at the reference site, and still visible industrial contamination at downstream sites, especially Karlovac, despite the cessation of industrial activities and wastewater effusion into the river.

herbicides ; metals ; nutrients ; organic contaminants ; river-water

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