Unveiling spatial variations in atmospheric CO 2 sources: a case study of metropolitan area of Naples, Italy.

In the lower atmosphere, CO 2 emissions impact human health and ecosystems, making data at this level essential for addressing carbon-cycle and public-health questions. The atmospheric concentration of CO 2 is crucial in urban areas due to its connection with air quality, pollution, and climate change, becoming a pivotal parameter for environmental management and public safety. In volcanic zones, geogenic CO 2 profoundly affects the environment, although hydrocarbon combustion is the primary driver of increased atmospheric CO 2 and global warming. Distinguishing geogenic from anthropogenic emissions is challenging, especially through air CO 2 concentration measurements alone. This study presents survey results on the stable isotope composition of carbon and oxygen in CO 2 and airborne CO 2 concentration in Naples' urban area, including the Campi Flegrei caldera, a widespread hydrothermal/volcanic zone in the metropolitan area. Over the past 50 years, two major volcanic unrests (1969-72 and 1982-84) were monitored using seismic, deformation, and geochemical data. Since 2005, this area has experienced ongoing unrest, involving the pressurization of the underlying hydrothermal system as a causal factor of the current uplift in the Pozzuoli area and the increased CO 2 emissions in the atmosphere. To better understand CO 2 emission dynamics and to quantify its volcanic origin a mobile laboratory was used. Results show that CO 2 levels in Naples' urban area exceed background atmospheric levels, indicating an anthropogenic origin from fossil fuel combustion. Conversely, in Pozzuoli's urban area, the stable isotope composition reveals a volcanic origin of the airborne CO 2 . This study emphasizes the importance of monitoring stable isotopes of atmospheric CO 2 , especially in volcanic areas, contributing valuable insights for environmental and public health management.