engleski

Radiocarbon application in environmental science and cultural heritage studies

The radioactive isotope of carbon, 14C or radiocarbon, is produced in the Earth’ s atmosphere and together with other carbon isotopes enters both the geochemical and the biological carbon cycles. It is a constituent component of all living organisms, in which the equilibrium between the decay and replenishment of 14C is established. After the death, only the radioactive decay occurs and this is the basis of the use of 14C for dating applications. The half-life of 14C is conveniently long (5730 y) to cover the period of development of human civilization. Even the so-called bomb peak in atmospheric 14C distribution in the second half of the last century can be used for various studies of behaviour of carbon in the environment, and in forensic and biochemical studies. Due to low natural abundance of 14C relative to 12C (10-12%), low specific activity (226 Bq/kg of carbon in modern samples) and low energy of electrons produced in the  decay of 14C, very sensitive and specific measurement techniques have been developed, as well as sample preparation procedures. This presentation will include short overview of modern measurement techniques of 14C, and then it will present some applications of 14C in archaeology and cultural heritage studies, as well as in the environmental sciences and geochronology, with an emphasis on those studies performed in the Zagreb Radiocarbon Laboratory. 14C in atmospheric CO2 has been measured at various sites more or less influenced by human activities. In the industrial city area during winter periods lower 14C atmospheric activities were measured than at the clean-air sites due to intense combustion of fossil fuels containing no 14C. During the refuelling outage periods of the nuclear power plant higher 14C activities in CO2 were detected in the close vicinity of the outflow, which returned to a normal value after a few months. Spatial distribution of 14C activities in biological samples (apples, corn) around the nuclear power plant showed the dependence on the distance and on the prevailing wind direction, and were also dependent on the time elapsed since the last refueling outage period. A study of radiocarbon, together with its stable isotope 13C, in geochemical processes can give some answers to important questions about environment, its pollution, changes in environment and climate. 14C was used in establishment of geochronology of secondary carbonates in karst environment in Croatia. Secondary carbonates (tufa and lake sediment) from the National Park Plitvice Lakes revealed the recent geological history of the lakes, which exist in the present form since the last Ice Age. 14C in recent (last 100 years) sediments helped in studies of the response of various geochemical systems to the bomb 14C and to recent global environmental changes. On the example of dating of charcoal samples from the two Early Neolithic settlements in Croatia, Slavonski Brod – Galovo and Zadubravlje – Dužine, that both belong to the Linear A phase of the Starčevo culture complex according to the typological and stylistic analyses of archaeological material, we will show how the archaeological interpretation of artifacts can get an added value by the use of the complementary 14C dating method. It is shown that the Linear A phase of the Starčevo culture lasted over an extended duration of about 1000 years in this region, and different phases in the development of the Galovo settlement were proved by the 14C dating. The 14C dating of the Late Neolithic Sopot culture proved its appearance during the existence of the Starčevo culture meaning that both cultures coexisted for several hundred years at a relatively small area in Eastern Croatia, approximately 50 km far from each other.

radiocarbon dating ; atmospheric 14C ; 14C in plants ; 14C in geology ; Plitvice Lakes ; Galovo

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