engleski

Mercury distribution in the surface sediments of the Kastela Bay

Kastela Bay is located at the eastern Adriatic coast of Croatia. Mercury was constantly introduced into the eastern part of the Bay since the opening of a chlor-alkaline plant in 1949 until 1990 when the plant was closed. The estimated influx of mercury to the Bay from 1949 to 1990 was about 200 000 kg. The environmental relaxation of Kastela Bay with respect to mercury was examined by the record of total mercuryconcentrations in sediment cores in 1987 and again in 1994. Total mercury values were obtained by digestion with HNO3 and H2SO4, reduction with SnCl2, and single-stage gold amalgamation/CVAFS for sediment studied. The accuracy of the results was also checked by the analysis of sediment reference material IAEA-356, certified for total mercury. The latest results for surface sediment of Kastela Bay (1994) show a considerable decrease in total mercury concentrations at the station in the vicinity of chlor-alkali plant compared to 1987 data. Unfortunately, results for other bay stations(significant increase of total mercury in surface sediment in relation to 1987) point to the fact that mercury has only spreaded all over the bay and has not been removed. Spreading of mercury throughout the bay is probably due to wave induced currents or bioturbation. Apart from surface spreading of mercury in the bay sediment, variations of totoal mercury with different depts of sediment in the vicinity of chlor-alkali plant were also studied. In general, the curve of mercury-depth profile showed a rapid decrease (from 6.9 ppm Hg in surface sediment to 0.4 ppm in 20 cm sediment depth).

mercury; Kastela Bay

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