engleski

Thallium concentrations in lake water and digestive gland of freshwater bivalves – a field study in two karst lakes in Croatia

Thallium is nonessential and highly toxic metal. It has high water solubility and shows the tendency of accumulation in living organisms. As a priority pollutant, it should be monitored both in water and in the organisms. So far, there are relatively few studies of Tl bioaccumulation in freshwater bivalves, especially in karst waters. We have studied Tl accumulation in the digestive gland of freshwater bivalves Anodonta spp. from two karst lakes in Croatia, Brljan and Visovac. The lakes are integral part of the Krka River ecosystem. Brljan Lake is situated upstream from Visovac Lake and is consequently more affected by the pollution of wastewaters from the Town of Knin. In Visovac Lake, organisms were sampled in shallow (1-3 m, VS) and deep (~13 m, VD) part of the lake, and at Brljan Lake only in shallow part (2-4 m, BR). In addition to Tl, we also analyzed the content of 23 trace elements and 4 macro elements in digestive gland in order to detect possible coaccumulation of Tl with other elements. Metals were determined by HR ICP-MS. Concentrations of dissolved Tl in water were very low in both lakes (5-6 ng/L). Whole digestive gland tissue of bivalves from VS location had about ten times higher Tl concentrations (0.039 μg/g) compared to the other two locations (0.004 and 0.005 μg/g at VD and BR location, respectively). Thallium concentration ranges in the cytosolic fraction of digestive gland were as follows: BR: 0.0008-0.004 μg/g, VS: 0.0002-0.0009 μg/g and VD 0.0004-0.0008 μg/g. Correlation analysis confirmed specific coaccumulation patterns at each of the investigated locations. Obtained results indicate low Tl exposure by water and suggest the need for further sediment research as a potential source of Tl for these bivalves.

Thallium ; Bioaccumulation ; Bivalves ; Karst lakes

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