Fig. 1

Study area, the route used during survey and dataset distribution. The survey was conducted in May 2023. (a) The blue line represents the route used during the survey. The selected subsets for Solfatara area (orange zone A), downtown Naples (green zone B), and airport (ice blue zone C) are shown. (b) Probability plot for concentration dataset. Global average value of airborne CO₂ concentration is reported as reference. (blue line indicates 423 ppm vol) for a comparison with the average CO₂ concentration over the target area (50% cumulative probability). (c) Histograms for both the oxygen isotope (δ¹⁸O–CO₂) and carbon isotope (δ¹³C–CO₂) compositions. (d) Three-dimensional view of the study area showing the atmospheric CO₂ concentration measurements at their respective locations. The height of the vertical bars is proportional to the concentration levels. The colour scale and bar height indicate that the highest CO₂ concentration was detected near the port. (e) Placement of the measurements within the study area. The colour scale is identical to that in subplot (d) and indicates the CO₂ concentration measured in the air. The maps (a), (d), and (e) were generated in Qgis 3.34 environment (https://qgis.org/download/).