engleski

Distribution of selected trace metals in coastal surface sediments from the middle and south Adriatic

The aim of the present work was to determine the content and spatial distribution of cadmium, lead, cooper and zinc in coastal surface sediments, and to establish their eventual dependences on organic matter content and granulometric composition of analysed sediments. Surface sediments samples (0-1cm) were taken at six locations along the east coast of Adriatic Sea yearly (in the period of 1997 to 2002). Trace metals were determined by the GF-AAS method using an atomic absorption spectrometer (Perkin- Elmer 1100 B). The organic matter content was determined as a weight loss after H2O2 treatment and heating at 450°C for 6 hours. Granulometric composition of sediment was determined by sieving and hydrometring according to Cassagrande. The results show that the highest trace metal concentrations are in front of town Šibenik (except for Cu which highest content is in front of town Dubrovnik), what is indisputable consequence of vicinity of polluted Krka river estuary and untreated town’ s urban wastewaters. The lowest values were found at station Stončica, located far away from land base sources of pollution, which concentrations are considered as natural and therefore used as reference station for Middle Adriatic. The comparison of the obtained results for coastal stations with “ natural content” for middle Adriatic (UNEP, 1994) shows that only station in front of Zadar is below average values for Cd, Cu and Zn, and could be named as unpolluted area with these metals. Unfortunately, values for Pb on all stations (except Stončica) are significantly over “ natural level” what indicate its anthropogenic input. Obtained results also show dependence of trace metal concentration on organic matter content and granulometric composition of sediments. According to this, higher metal concentration and organic matter content were found in fine-grained sediment. Since the concentrations of analysed metals in surface sediments generally are not too high, it may be concluded that the investigated coastal area (except in front of Šibenik) is not heavily polluted.

trace metals; Adriatic Sea; sediment

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