Radiocarbon activity of gases in urban surface air in Bratislava, Slovakia

Carbon-containing gases in the atmosphere are important for the study of carbon cycle dynamics and anthropogenic influence on these environmental processes. Radiocarbon analysis is an excellent tool for studying sources of these gases and their variations. Carbon dioxide is the most abundant and most important of these gases and this study presents results of radiocarbon measurements of carbon dioxide samples collected at the campus of Comenius University in Bratislava, Slovakia from 1967 to 2025. This record of radiocarbon activity is characterized by decreasing intensity of anthropogenic effects in last 30 years. Local Suess effect (dilution of radiocarbon activity by radiocarbon-free fossil carbon dioxide) is clearly weaker in recent decades. The influence of Slovak nuclear power plants (input of excess anthropogenic radiocarbon) is also significantly smaller in last decades compared to the beginning of radiocarbon activity record from Bratislava. Comparison of two sampling stations located in Bratislava with clean air data showed that there is significant contrast between local Suess effect intensity observed at locations relatively close to each other within the city, but in a different setting in terms of local fossil carbon dioxide sources. Radiocarbon analysis of carbon dioxide in Bratislava has also been recently supplemented by sampling and analysis of carbon monoxide and hydrocarbons present in the atmosphere. The results show that their radiocarbon levels are considerably influenced by their fossil sources, leading to their very low radiocarbon activity compared to expected background values.