engleski

Anthropogenic pollution in Croatian and Bosnian karst waters and lake sediments

Within the EU-Project ICA2-CT-2002-10009 of the European Union we try to investigate the anthropogenic pollution after the war in Croatia and Bosnia-Herzegovina and its consequences to the karst ecosystem in the border area between these two countries. The area is important for tourism (Plitvice National Park) and the karst groundwater system connected to the Una River watershed contains resources for drinking water supply of the city of Bihac. Within the project, Croatian and Bosnian scientific institutions cooperate with the University of Barcelona (Spain) and the GGA-Institut (Germany). The project investigates the interconnected system of lake sediments, lake waters and karst ground waters. Both the amount of usable water from river Una and karst springs in the surroundings of Bihac as well as its degree of pollution are investigated by geochemical and isotope hydrological methods. Sources of pollution here are local industries. Waste waters from tourist accommodations contribute to the pollution of the ecosystem in the Plitvice national park, where lake eutrophication is an important task. Surface sediment cores obtained by scuba divers in several lakes will be dated using gamma spectrometry and 210Pb/137Cs. Together with the geochemical studies in the sediments and lake waters a chronology of lake water pollutants will be established. A final goal is an integrated hydrological model of the Plitvice catchment and its receiving streams represented in a geographical information system. Within the framework of this project the talk will concentrate on the following subjects: • Determination of mean residence time of karst springs ( 18O/ D, Tritium/3Helium, CFC/SF6) • Time series of stable isotope of water ( 18O/ D) in the Plitvice Lakes, karst springs, Una River and rain water composition • Possible coupling of lake water and karst groundwater in the Plitvice and Una River catchments • Determination of sedimentation rates in lakes of Plitvice National Park (gamma spectrometry: 210Pb, 137Cs) • Geochemical and isotopic sediment-water interaction of the lake sediments The first results for stable isotopes, tritium and CFC/SF6 allow some preliminary conclusions: The stable isotopes of water plot above the global meteoric water line (GMWL) with a deuterium excess between 10 and 16. So most samples seem to have some influence from the Mediterranean area, where higher deuterium excess than 10 prevails. The plot shows also two clusters with a boundary roughly at  18O = 9.7‰ : values more positive are from Una River, values more negative are from the Plitvice catchment and its tributaries. As expected from hydrogeologic arguments some springs feeding Una River (Klokot, Privilica) have the stable isotope signature of the Plitvice catchment suggesting a karst hydrologic connection of the two systems. For the Bijela Rijeka Spring a twenty-year time series of tritium exists (Fig. 2, 3) whereas other springs have been sampled for isotopic tracers the first time during this project. Even with the long time series no unique MRT can be determined for this spring with tritium alone, MRTs of 2-7 or 50-70 years would be possible. The combined results for tritium and CFC/SF6 measurements show that the Mean Residence Time is short, ranging between 1 and 5 years. The preliminary CFC and SF6 results indicate recharge temperatures around the mean annual temperature whereas the hydrologic regime suggests main recharge during the winter rain period. No significant anthropogenic CFC contaminations were detected.

drinking water; Plitvice National Park; war consequences; age determination; stable isotopes; CFC/SF6; T/3He; sediment dating; gamma spectrometry

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