A comparison of anthropogenic mercury pollution in Kastela Bay (Croatia) with pristine estuaries in Oere (Sweden) and Krka (Croatia)

• Published in: Marine pollution bulletin Vol. 44; no. 10; pp. 1152 - 1157
• Main Authors: Kwokal, Z, Franciskovic-Bilinski, S, Bilinski, H, Branica, M
• Format: Journal Article
• Language: English
• Published: 01-10-2002
• Subjects: Brackish; Croatia, Kastela Bay; Croatia, Krka R; Sweden, Oere R; MED, Croatia, Kastela Bay; Croatia, Krka Estuary; Sweden, Oere Estuary; ANE, Sweden, Vaesterbotten, Oerefjaerden; Sweden; MED, Croatia, Krk, Krka Estuary
• ISSN: 0025-326X

Anthropogenic mercury pollution was studied in Kastela Bay (Croatia), 10 years after chloralkaline plant (PVC) stopped production. The concentration of total mercury determined in sediments which are composed mainly of calcite and quartz, are in the range 14,280-30,400 ng/g. The values are higher than reported in the literature for Elbe and Seine estuaries and also above 25,000 ng/g used for criterion in remediation project in Minamata Bay. The concentration of methylmercury 6.05-36.74 ng/g are typical for slightly to highly contaminated estuarine sediments. The low ratio of methylmercury to total mercury found in sediments of Kastela Bay is in the range 0.04-0.18%. It can be explained that in this region predominate conditions which do not promote in-situ methylation. Sediments were found to be highly anoxic. Concentrations of total mercury in unfiltered surface waters are in the range 69-145 ng/l and in unfiltered bottom waters in the range 230-1,418 ng l super(-1). High concentrations found in bottom waters suggest that either resuspension or partial dissolution of sediments takes place. An experiment performed on filtered and unfiltered waters showed that about 85% of total mercury in surface water and almost 100% in bottom water was retained on 45 mu m filters. To demonstrate contrasts, two pristine estuaries from norths and south Europe were studied. Silicious sediments of Oere estuary (Sweden) and calcareous sediments of Krka Estuary (Croatia) have total mercury concentrations close to accepted background level. The ratio of methylmercury to total mercury is less than or equal to 1% in all samples with one exception. The highest observed ratio (2.70%) was in the surface sediment from E2 station in Krka estuary measured in March 2000. This location is suitable for studying methylmercury formation in pristine environment.