Naslov
Recent lake sediments in the Plitvice Lakes, Croatia - the record of environmental contamination

Autori
Horvatinčić, Nada ; Barešić, Jadranka ; Obelić, Bogomil ; Krajcar Bronić, Ines ; Vreča, Polona

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
19th International Radiocarbon Conference, Keble College, Oxford, 3rd - 7th April, 2006, Abstracts and Programme / - Oxford : University of Oxford, 2006, 219-220

Skup
19th International Radiocarbon Conference

Mjesto i datum
Oxford, Ujedinjeno Kraljevstvo, 03.04.2006. - 07.04.2006

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
14C; Plitvice Lakes; lake sediment

Sažetak
Lake sediments as the results of calcium carbonate precipitation from the dissolved inorganic carbon (DIC) record environmental conditions at the time of precipitation. In order to study possible influence of human activities on lake water and sediment during approximately last 100 years, we used 40-45cm long surface cores taken from four karstic lakes in the area of the Plitvice Lakes system in Croatia. The Plitvice Lakes consist of a series of lakes connected with waterfalls. The area is characterized by a strong process of tufa precipitation forming tufa barriers. Sediment cores were taken at five locations in downstream direction: Lake Prošće (water depth 19 m), Lake Gradinsko (5m), Lake Kozjak K-2 (2m), Lake Kozjak K-1 (21m), Lake Kaluđerovac (3m). Samples for analyses were cut from the frozen sediment cores into 1-2 cm thick layers and dried at 120oC. The following analyses have been performed: mineralogical and organic elemental analyses, analyses of radiocarbon isotope 14C and stable isotopes 13C and 18O, 137Cs and 210Pb measurements, and trace element analyses. Steady decrease of organic fraction from the uppermost Lake Prošće (7.5-10.9%) to the lowermost Lake Kaluđerovac (1.9-3.4%) is observed. The mineral composition of sediments shows that the major component at four locations is calcite (80-99%), showing slight increase with depth.  13C values for these sediments range between -9 and -7‰ and these values correspond well to the previous measurements of  13C values of tufa and lake sediments from the Plitvice Lakes area. At these locations the calcite in sediment is mainly formed by authigenic precipitation from DIC in lake water. The 14C activity of sediments shows steady increase from the uppermost Lake Prošće (mean value 68.8 pMC), through Lake Gradinsko (mean value 76.5 pMC), to the lowermost Lake Kaluđerovac (mean value 81.2 pMC). The peak in 14C activity in each sediment core is observed between 5-10 cm and it is the consequence of bomb-produced 14C activity in the atmosphere in the sixties of last century. According to the 14C and 137Cs activity distribution in the sediments the approximate sedimentation rate of lake sediments was determined. Roughly approximated, the upper first 10 cm of most sediments correspond to the last 50 to 100 years. Location in Lake Kozjak K-2 is an exception in all analyses performed: much higher organic component in the sediment (11.4-36.6%), lower calcite concentration, more positive  13C (between – 5.5 and – 5.0‰ ), lower 14C activity of the carbonate component (30-35 pMC) and higher concentrations of some trace elements. The site is close to the mouth of Rječica brook to the Lake Kozjak and transport of some mineral components and organic material from the stream of Rječica is possible.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Geologija, Kemija

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