PURPOSES : The objective of this study is to figure out the trend and characteristics of fine particulate matter (PM2.5) and nitrogen oxide (NOx) concentration in underpass sections. The effect of traffic and meteorological condition on PM2.5 / NOx concentration was analyzed using field monitoring data.
METHODS : Based on the literature review, PM2.5 and NOx concentration data were monitored using DustTrak II aerosol monitoring system and Serinus 40 oxides of nitrogen analyzer, respectively. Meteorological and traffic information was collected using automatic weather system and traffic volume counter, respectively.
RESULTS : PM2.5 has a positive and negative correlation with relative humidity and wind speed, respectively. Meanwhile, NOx was found to have no correlation with meteorological conditions. The NO/NO2 ratio tends to change with traffic volume, indicating higher correlation between NO and traffic volume; the observed NO2 is mostly a secondary material produced by NO oxidation.
CONCLUSIONS : Our study provides clear characteristics of NOx and PM2.5 and correlations with meteorological and traffic information in the underpass sections. It is found from this study that the increase in wind speed causes reduction in the concentration of PM2.5 owing to the diffusion and dispersion phenomena. On the other hand, the meteorological conditions were found to barely have correlations with NOx concentrations in this study. The traffic volume could significantly affect the NOx concentration and NO / NO2 ratio, which is directly correlated to the emissions from vehicles.

ABSTRACT
1. Introductuon
    1.1. Research Background
    1.2. Research Objectives
2. Site Descriptions and Measurement Methods
3. Results and Discussion
    3.1. Comparison of NO2 and PM2.5 in test section andatmospheric measurement station
    3.2. Effect of meteorological conditions on the NOx andPM concentration
    3.3. Effect of traffic condition on the NOx and PMconcentration
4. Conclusions
REFERENCES

• Kim Moonkyung(Korea Institute of Civil Engineering and Building Technology) | 김문경
• Lee Jong Won(Korea Institute of Civil Engineering and Building Technology) | 이종원
• Lee Sang Hyuk(Korea Institute of Civil Engineering and Building Technology) | 이상혁
• Park Hee Mun(Korea Institute of Civil Engineering and Building Technology) | 박희문 Corresponding Author