engleski

Comparative Analysis of Metal Accumulation in Liver and Muscle of Northern Pike from the Mrežnica River: Spatial and Tissue-Specific Differences

The lower part of the Mrežnica River has long been exposed to industrial pollution from the cotton industry near the Town of Duga Resa. To assess the level of metal pollution of the Mrežnica River affected by anthropogenic activities, total metal concentrations were measured in liver and muscle of northern pike (Esox lucius), as a representative fish species. The liver was selected as the main metabolic site in organism, while the muscle, as the edible part, could pose a health risk to humans in case of elevated metal levels. Fish were caught in autumn 2021 at two sites: upstream of the known pollution source as the reference site (REF) and downstream of the Town of Duga Resa (DRT) as the contaminated site. Tissue samples were digested with mixture of HNO3 and H2O2, and metal concentrations (As, Bi, Cd, Co, Cs, Cu, Fe, K, Mg, Mn, Na, Pb, Rb, Se, Tl and Zn) were measured using HR ICP-MS. The concentrations of Pb were below detection limits in both organs, and of Cd only in the muscle. Obtained results confirmed liver as metabolically more active organ than muscle, as accumulation of most elements was 2-250 times higher in liver. The most prominent difference was observed for Fe, Cu, Co and Zn at both investigated sites, with concentrations in the liver higher 10-250 times compared to the muscle. However, Cs, K, Mg and Rb showed higher bioaccumulation in the muscle. Despite different roles and structures of the two organs, they reflected environmental conditions in a similar manner. Significant differences between REF and DRT sites were evident for Bi, Rb and Se in both organs, and for Cd, Mn and Zn only in liver. Bismuth and Zn showed higher levels at DRT, whereas enhanced accumulation of Cd, Mn, Se and Rb was observed at REF. These results can be partially explained by differences of metal exposure from water and sediments. Namely, patterns of Bi, Cd, Mn, and Zn are consistent with their exposure levels in sediments or water [1], while the causes of increased Se and Rb accumulation at REF should be further investigated. Some spatial variability in both organs were also observed for As, Co, Fe, K, Mg and Na, but were not shown significant. Comparison to literature revealed that metal(loid) concentrations in analyzed organs of northern pike indicate certain increase of bioaccumulation due to anthropogenic pressure. The concentrations in the fish muscle, however, were acceptable at both sites based on the national and European legislations [2, 3], which provide permissible levels for As, Cd and Pb. Therefore, moderate impact of the historical contamination was observed in the Mrežnica River, and further monitoring of the environment and biota is still recommended

metals ; fish ; ICP-MS ; Mrežnica River

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