engleski

Exchange processes of carbon isotopes 14C and 13C in the karst environment

Natural cosmic-ray produced radiocarbon 14C is a part of the CO2 cycle and through the atmosphere-biosphere-hydrosphere exchange process has been introduced to the environment. Anthropogenic disturbance of the natural 14C activity caused by nuclear tests, nuclear power plants and fossil fuel combustion has been recorded in the atmospheric CO2. In the karst environment, which includes water, carbonate sediments (speleothem, tufa, lake sediment), soil and vegetation (terrestrial and aquatic plants), the exchange processes within the CO2 – dissolved inorganic carbon (DIC) – CaCO3 system play an important role. This system is very sensitive to any change in the atmosphere, and response to the contamination is very fast.  13C values of each material give additional information of carbon origin and geochemical processes in the system. Few examples of isotopic studies in karst environment from several sites in Croatia and Slovenia will be presented: 1) The exchange processes of 14C and 13C between atmospheric CO2, DIC in water and recent carbonate precipitated in surface water in form of tufa and lake sediment in the Plitvice Lakes and Korana River ; 2) 14C activity in recent tufa in Krka and Zrmanja rivers in Croatia, and Krka River in Slovenia ; 3) 14C activity in recent speleothems from caves of the Dinaric Karst in Croatia and the Postojna Cave in Slovenia ; 4) Distribution of 14C activity in surface soil in Plitvice Lakes and Postojna area ; 5) 14C activity of atmospheric CO2 inside and outside the Postojna Cave, 6) 14C activity in recent plants (terrestrial and aquatic) and shells. Environmental samples from different sites were collected in the period 1974-2008. Distribution of 14C in the karst environment will be compared with 14C activity of atmospheric CO2 that has been continuously monitored in monthly samples in Zagreb area. The response of different environmental materials to the bomb 14C activity will be discussed.

radiocarbon; stable isotopes; Karst environment

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