engleski

Comparison of two mercury polluted coastal environments in the Adriatic Sea

Anthropogenic mercury pollution was studied in Kaštela Bay (Croatia), 10 years after chlor-alkali plant (PVC) stopped production. During the operation of the plant, liquid mercury was released in the sea water. The concentrations of total mercury determined in sediments in vicinity of the plant (50 - 300 m seaward) are in the range 14.28 to 30.40 ľgg-1. These values are higher than measured from 1985 to 1988, as reported by Zvonarić (1991). The concentrations of total mercury in Kaštela Bay are lower than determined by Hines et al. (2000) in Gulf of Trieste, Italy, at D6 station. This station is close to the estuary of Isonzo (Soča) River. This location was influenced by pollution from Idrija mercury mine (Slovenia), operating for 500 years till recently. Cinnabar, HgS entered the drainage basin. At both locations the values of total mercury are above 25 mg kg-1, used for criterion in remediation project in Minamata Bay (Hosokawa, 1993). It should be mentioned that from "Chisso Ltd" methylated mercury was released into Minamata Bay from 1932-1968, resulting in Minamata Desease discovered in Japan in 1956, as reported by Harada (1995). The concentrations of methyl mercury in the range from 6.05 to 36.74 ngg-1 in Kaštela Bay (Croatia) are typical for slightly to highly contaminated estuarine sediments. Inspite of very high total mercury concentrations at the D6 station in Gulf of Trieste, the concentrations of methyl mercury are <5 ngg-1 (Hines et al., 2000), what is typical for slightly contaminated estuarine sediments. The ratio of methyl mercury to total mercury in both polluted locations is lower than found in pristine estuarine environments, such as Öre estuary (Sweden) and Krka estuary (Croatia). In Kaštela Bay this ratio is in the range 0.04 to 0.18% and at D6 station in the Gulf of Trieste is from 0.008 to 0.015%. The possible natural defence processes in these regions will be discussed in view of earlier studies (Bilinski and Jusufi, 1980; Gilmour and Henry, 1991; Hintelmann and Wilken, 1995; Tossell, 1998). In highly anoxic sediments, as found in Kaštela Bay, (p? was from -3.49 to -5.73) the conditions seem to be similar as described by Gilmour and Henry (1991), which don't promote in situ methylation. In both locations, in which enters as inorganic mercury into the seawater, there is no indication of significant methylation. Optimystical scenario would be that Minamata Desease will not develop.

mercury; methylmercury; Kaštela Bay; Gulf of Trieste; Idrija; Soča river; pollution

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