engleski

Thalium accumulation in the hepatic and gill soluble fractions in brown trout (Salmo trutta Linnaeus, 1758) from from the Croatian river Krka

Thalium in rivers is naturally presented in low concebtrations, even extremely low in karstic rivers, which makes them very sensitive to anthropogenic influence. Nowadays, there is an increasing demand for thallium in the high-technology and future-technology fields and increased exposure of freshwater fish to Tl can cause serious harmful effects, consequently influencing freshwater biodiversity and possibly human health. Because it's toxicity even at very low concentrations, higher water solubility compared to other heavy metals, mobility, more bioavailability and tendency to bioaccumulate in living organisms, Tl is included in the list of priority pollutants by the US Environmental Protection Agency [1] (Das et al., 2006) and should be regularly monitored in the natural waters and organisms [2]. Increased exposure of freshwater fish to Tl can cause serious harmful effects, consequently influencing freshwater biodiversity and possibly human health. The aim of this study was to obtain the information on the concentration of Tl in cytosol which is presumably available for the interactions with vital cell components and consequently could cause toxic. With that purpose, determination of Tl concentrations was performed in the cytosolic fractions of liver as main detoxification organ and gills as organ with direct contact to the water of 68 brown trout specimens (S. trutta Linnaeus, 1758) caught in the Kriva River which were obtained after tissue homogenization and centrifugation at 50, 000xg. Measurements were performed using high resolution inductively coupled plasma mass spectrometer (Element 2, Thermo Finnigan) at two different contaminated sampling points (Krka River spring and Krka River downstream from Knin) in two seasons (October 2015 and May 2016). Thallium is generally present in the freshwater ecosystems in very low levels [3]. The concentrations of Tl were higher in liver cytosol in comparasion to the metal concentration in gill cytosol in both sampling sites, in both sampling seasons. Cytosolic Tl concentrations in the soluble fractions of organs (liver and gill) were significantly higher at the Krka Spring site in comparison to Krka River downstream from the town Knin in all studied campaigns and did not follow the spatial distribution of dissolved Tl in the river water, where the total dissolved Tl levels in water were similar in both sites, in both seasons. This could indicate influence of some Tl natural sources and processes such as accumulation of Tl in organs through food and sediment. The correlations with biometric parameters (total fish mass) were insignificant, whereas the levels of Tl measured for males and females were comparable, without observation of significant differences in neither tissue in both seasons. Tl increase in both organs gill and hepatic soluble fractions of the brown trout restricted to the one site in both both seasons, without the dependence on the fish physiology, points to the necessity of further investigation of fish accumulation of Tl through sediment and food uptake in the regular monitoring of the natural waters.

thallium ; liver ; gills ; brown trout ; bioaccumulation

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