Abstract
Aim: Road tunnel construction, especially in urban areas, leads to the reduction in the emission of solid and gaseous pollutants within the area of the constructed tunnel, and at the same time to a significant increase in the concentration of this pollution in the areas where the exhaust air is discharged from the tunnel. The article presents a simulation of how nitrogen dioxide coming from car exhaust spreads in the area of the analyzed street and a simulation of changes in its concentration in the case of tunnel building with longitudinal ventilation with and without air purification system. At the same time analysis of the effectiveness of using air purification technology in tunnels was carried out.
Introduction: Reports concerning air quality in Europe place Poland among the most polluted countries. Exhaust emission from cars is the main reason for the high concentration of air pollutants in cities. Construction of road tunnels is one of the methods to reduce the content of solid and gaseous pollutants in the air in cities. This solution leads to a significant reduction in the emission of pollutants, especially gaseous ones, within the area of a tunnel; however, the ventilation air discharged from the tunnel generates locally, in the areas of tunnel portals, an increased concentration level of solid and gaseous pollutants. All over the world, in city tunnels, systems of purifying large volumes of ventilation air streams from solid and gaseous pollutants are used – examples are Mont Blanc tunnel in Alps connecting Chamonix in France and Courmayeur in Italy and the M30 tunnel in Madrid, where ventilation air from the tunnels is purified before it is removed to the atmosphere.
Methodology: In order to study the impact of a road tunnel on the concentration levels of selected air pollutants, a location included in the conceptual design of a road tunnel in Warsaw, along Wawelska Street, was selected. The emission of selected gaseous pollutants from car engines was modelled using Computational Fluid Dynamics for the current situation on Wawelska Street (vehicle traffic on the road), for the construction of a tunnel with a longitudinal ventilation without an air purification system, and for the construction of a tunnel with longitudinal ventilation with an air purification system. The levels of air pollution concentration for the analysed cases were juxtaposed with one another.
Conclusions: The comparison of the results of numerical analyses with the results of the air pollution concentration study in the area of Wawelska street in Warsaw, which was conducted by the Warsaw University of Technology staff, confirmed the adopted numerical modelling assumptions for the current state. The results of the analyses concerning the predicted concentration of air pollution in the variant of tunnel construction without an air purification system showed a significant reduction in pollution in the area of Wawelska Street and largely exceeded pollution concentration limits in the area of the tunnel portals. Moreover, the results of numerical analyses confirmed that the construction of a tunnel with an air purification system was the most favourable solution, leading to the reduction of pollution in the area of Wawelska Street in Warsaw.
Keywords: tunnel, tunnel ventilation, air purification, pollutants
Type of article: review article