Daily and seasonal variation of CO2 in the city of Rome in relationship with the traffic volume

Abstract Measurements of carbon dioxide (CO 2 ) concentration carried out in the city of Rome showed an increase from 1995 (367±29 ppm mean yearly value) to 2004 (477±30 ppm, mean yearly value). The annual trend showed a peak in winter, 18% greater than the summer one correlated to traffic density (35±4 and 29±3 cars min −1 mean winter and summer value, respectively). The weekly trend had the lowest values (414±19 ppm) during the weekends when traffic density was 72% reduced. The daily trend had a peak in the early morning when traffic was the highest and the atmosphere was more stable. The critical zones of the city (B zones) had 3.5% CO 2 concentration higher than the park (D zone) and 18% more than the control zones (E zones). An increase of air temperatures from the surrounding zones (20.0±4.1 °C) to the centre of the city (28.9±1.2 °C, mean between A and B zones) was observed.