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

Measurements of carbon dioxide (CO2) 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% CO2 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 degrees C) to the centre of the city (28.9 +/- 1.2 degrees C, mean between A and B zones) was observed.