Air quality monitoring of underground road tunnel

• Main Author: Tok, Kian Ming.
• Other Authors: Chang Wei-Chung
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Environmental engineering::Environmental pollution
• Online Access: http://hdl.handle.net/10356/15936
• Institution: Nanyang Technological University

The project is a study of air quality in an underground road tunnel in Singapore. It is a double-tube, unidirectional which is 8.5km in length. The aim of the study is to examine the roadside concentration of CO, NO2, SO2, VOC and particulate matter (PM). In addition, temperature and relative humidity are also taken into consideration to ensure the comfort and safety of road users. The project consists of 2 experiments. The first experiment is a 3 day (2 weekday, 1weekday) monitoring of above parameters at two separate sites (Site 1 - south bound 6.5km from exit and Site 2 - 3.9km from exit) in the south bound tunnel. The second part of the experiment is a mobile study during the afternoon peak hour to examine the air quality of the entire tunnel. Analysis has been conducted and parameters are used in comparison to the tunnel sensor to ensure its accuracy and proper control of ventilation system. Moreover, the relationship of various pollutants is evaluated. The results of the study have shown that the temperature of the tunnel is on an average 1.6°C higher than the measurements from the tunnel sensor at Site 1. Higher average pollution level is detected on weekend than weekday due to the higher traffic counts on weekend. A moderate correlation is also found between PM2.5 and visibility of tunnel. In addition, a good correlation can be drawn between PM2.5 and CO, as well as PM2.5 and NO2 from the drive through experiment. This indicates that there is a high possibility that the three pollutants come mainly from the same source (tailpipe exhaust). Generally, pollutants level increases with increasing distance from the tunnel entrance because of the piston effect. Consequently, the peak of CO and NO2 is found to be in P20K location of the south bound tunnel because of the lack of ventilation. The experiment has shown that PM2.5 concentration can be a good indicator of pollutant levels due to its good correlation with CO and NO2 concentrations. Lastly, although the pollutant levels rarely exceed the safety limits of NEA, a better air management program can be implemented to further improve the air quality and safety of drivers.