engleski

Carbon isotope composition (14C and 13C) of the atmospheric CO2 at several locations in Croatia

Radiocarbon (14C) is both the cosmogenic and anthropogenic isotope. Anthropogenic sources of 14C are atmospheric nuclear bomb tests, various nuclear facilities and fossil fuel combustion. The bomb-produced 14C has been globally distributed across the planet and can be considered as a new- natural level (clean-air sites). Combustion of fossil fuels that do not contain 14C causes increase of atmospheric CO2 concentration and depletion of local 14C levels, while nuclear sources increase local or regional atmospheric 14C level. Naturally produced CO2 and that formed by fossil fuel combustion are characterized by different content of the stable isotope13C (delta13C values) in addition to their different 14C content. Therefore, the carbon isotope composition (13C and 14C) of the atmospheric CO2 can indicate sources of CO2 at each location, if it is far from nuclear facilities. 14C activity in the atmospheric CO2 in Zagreb, Croatia, has been monitored since 1985. Recently we have been monitoring carbon isotope composition at several other locations in Croatia (city of Rijeka and rural areas around Zagreb and Rijeka) with the aim of determining influence of fossil fuel combustion on atmospheric 14C activity and 13C values at different locations with the hypothesis that the urban sites are affected by fossil fuel uses. Rural locations show higher 14C activities (by about 2 pMC – percent Modern Carbon) and higher delta13C values than the urban sites in accordance with the hypothesis. The difference is larger during winter (about 2.4 pMC) due to more intense fossil fuel combustion in the cities.

14C ; 13C ; atmospheric CO2 ; sampling methods ; measurement methods ; Croatia

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