Photocatalytic performances in a city tunnel in Rome: NOx monitoring results

This paper deals with the results of two environmental monitoring campaigns entailing the analysis of NOx levels registered before and after the renovation work of the “Umberto I” tunnel in Rome, Italy. The results of the data collection highlighted an efficient abatement of pollutants by the photocatalytic treatment of the tunnel vault with a cement-based paint, as evidenced through the lower concentrations found after the renovation. A NOx reduction of about 20% was calculated in the center of the tunnel (as an absolute comparison between the two periods), whereas a NOx reduction of over 50% was calculated in the same position, considering the reference data registered in the official stations of the city of Rome (Official Environmental Agency – ARPA). The duration of the monitoring campaigns performed seems to be considered significant from the statistical point of view, unlike all previous experiments which were carried out on the photocatalytic materials. This renovation project can prove out to be a very useful reference for the wide program for a sustainable upgrading of tunnels in Europe, according to the Directive 2004/54/EC on road tunnel safety.