Field measurements of the environmental parameter and pollutant dispersion in urban undersea road tunnel

The urban undersea road tunnels located between the islands in the seaside city are featured with high frequent traffic congestions and a strict environmental control standard. A reasonable ventilation system need be built for normal and emergency operation. The fresh air requirement for diluting vehicle pollutants during normal operation can be dominant in urban tunnel. This in turn requires that the main environmental parameters and vehicle pollutants of the tunnel should be sufficiently accurate. Thus, a field measurement was conducted in a real-world urban undersea road tunnel. The temperature, humidity, air velocity, CO, NO2 and PM concentration were tested along the tunnel. The tested results showed that the maximum temperature and relative humidity at the tunnel outlet was 35 degrees C and 94.5% respectively. The maximum NO2 concentration at the tunnel outlet was 3.73 ppm, the PM concentration at the bottom and outlet of the tunnel were 2030 mu g/m(3) and 1760 mu g/m(3) respectively, which exceeded the design threshold value. The emission of CO and NO2 in the uphill section was 2.78 and 1.28 times that in the downhill section respectively. The results can provide beneficial suggestion in ventilation system design and environmental assessment for urban undersea road tunnels, and the basic data in this paper can be used for relevant standard and norm compilation.