G01_P08

Atmospheric CO₂ carbon isotope composition in urban and clean areas of costal Northern Croatia

Sironić A¹, Hess E², Borković D¹, Kanduč T³, Barešić J¹, Krajcar Bronić I¹

¹Ruđer Bošković Institute, Zagreb, Croatia, ²Department of Physics, University of Rijeka, Rijeka, Croatia, ³Department of Environmental Sciences, Jožef Stefan Institute, Ljubljana, Slovenia

Fossil fuel combustion decrease ¹⁴C activity and ¹³C composition of atmospheric CO₂, which is also known as the Suess effect. For one year (2021), we have been monitoring carbon isotope composition of atmospheric CO₂ at locations under maritime influence of the Adriatic Sea: coastal city of Rijeka and at two clean air sites in vicinity, Gornje Jelenje and Parg with mountain climate.

Carbon isotope composition at all sites shows seasonal variation, with the lowest ¹⁴C activities and δ¹³C in winter-spring, and the highest in summer, ranging from -41.3 to 25.2 ‰ for Δ¹⁴C and -13.1 to -11.3 ‰ for δ¹³C, respectively. Rijeka has systematically the lowest and Parg the highest Δ¹⁴C, however δ¹³C at the sites are not statistically different one from another. Leaves of deciduous trees were also collected. Their Δ¹⁴C reflect the trend of atmospheric Δ¹⁴C, being the lowest at Rijeka and highest at Parg.