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Geochemical and isotopic research at Plitvice Lakes system (CROSBI ID 540267)

Prilog sa skupa u zborniku | sažetak izlaganja sa skupa

Barešić, Jadranka ; Horvatinčić, Nada ; Krajcar Bronić, Ines ; Sironić, Andreja ; Obelić, Bogomil ; Vreča, Polona Geochemical and isotopic research at Plitvice Lakes system // Guide book and abstracts, 16th International Karstological School "Classical Karst": Karst Sediments / Nadja Zupan Hajna, Andrej Mihevc (ur.). Postojna: Znanstvenoraziskovalni center SAZU, 2008. str. 61-62

Podaci o odgovornosti

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

engleski

Geochemical and isotopic research at Plitvice Lakes system

The Plitvice Lakes, situated in the Dinaric karst in Central Croatia, consist of 16 lakes of different sizes, connected by streams and waterfalls. The altitude of the area ranges between 636 m and 505 m a.s.l., the climate is continental, the 5-year average air temperature is 8.7°C, and the average yearly precipitation is 1473 mm. The lakes receive water from two main springs (Bijela Rijeka and Crna Rijeka) and two tributaries (Rječica and Plitvica). The lakes are characterized by intense calcium carbonate precipitation from the water, forming tufa barriers and fine-grained lake sediments. The surrounding area is covered largely with deciduous forests. The area is sparsely populated, is protected as a National Park, and is included in the UNESCO World Heritage List. Consequently, human activities in the lake watersheds are relatively limited. However, numerous tourists visit this area every year. Intense plant growth has been observed in some lakes and water streams at the Plitvice Lakes area and here we investigate whether this phenomenon is a consequence of anthropogenic pollution or due to naturally produced organic matter in the lakes. We applied mineral and organic fraction analyses, trace elements, measurement of stable and radioactive isotopes of surface lake sediments in four different lakes: Prošće, Kozjak, Gradinsko and Kaluđerovac. Kozjak Lake with confluence of Rječica tributary is investigated more detail so sediment is sampled at four sites. Lake sediments consist mainly of autochthonous carbonates (mainly calcite) with higher sedimentation rate in small lakes. Sediments from the two large lakes, Prošće and Kozjak, showed constant stable isotope profiles for the carbonate fraction and full agreement between the 137Cs and 210Pb chronologies. Sediments from the two small lakes, Gradinsko and Kaluđerovac, showed synchronous increases in 14C and  13C in the surface 10 cm of sediment and disturbed 137Cs records. All lakes showed an increase in a14C in the carbonate sediments above the first occurrence of 137Cs which was interpreted as a damped (~10 pMC increase in a14C), and decades-delayed consequence of the thermonuclear bomb-induced increase in a14C in atmospheric CO2. For the small lakes, increased  13C in the last two decades and part of the a14C increase is probably due to an increase in primary productivity that enhanced biologically-induced calcite precipitation with concomitant changes in the carbon isotopic composition of carbonate sediments.  13C values of a near-shore sediment core close to the confluence of the Rječica tributary of Lake Kozjak showed that the carbonates in this core are a mixture of autochthonous and eroded allochthonous mineral carbonate. Fraction of organic material and the C/N ratio are the highest in this core indicating that the organic matter is mainly of terrestrial origin. Tributary influence decrease rapidly with increasing distance from tributary Sedimentation rate at this core site was high, but it could not be quantified by 210Pb or 137Cs. The content of organic matter, C/N ratios, isotopic measurements in sediment organic matter (δ 13C, 14C) and measurement of total 15N in all Plitvice sediments/cores showed mainly autochthonous origin of sediment material. There is no significant difference among the trace element concentration in the upper segment of all cores, deposited approx. during last 50 years when higher anthropogenic influence is expected due to development and touristic activity, and the lower part of the cores, corresponding to the period approx. 100-200 years before present. The content of trace elements and organic matter in sediments decreases from the uppermost lake downstream. According to our results there is no indication of significant recent anthropogenic pollution in water and sediment.

Plitvice; lake sediments; isotopes

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Podaci o prilogu

61-62.

2008.

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objavljeno

Podaci o matičnoj publikaciji

Guide book and abstracts, 16th International Karstological School "Classical Karst": Karst Sediments

Nadja Zupan Hajna, Andrej Mihevc

Postojna: Znanstvenoraziskovalni center SAZU

Podaci o skupu

16th International Karstological school "Classical Karst". Karst Sediments.

poster

16.06.2008-21.06.2008

Postojna, Slovenija

Povezanost rada

Fizika, Geologija, Kemija