This study investigated the association between PM2.5 concentrations obtained with portable real-time monitors and those obtained with gravimetric methods in national urban air-quality monitoring sites in Seoul, South Korea. We used the SidePak AM510 Personal Aerosol Monitor (TSI Inc., 500 Cardigan Road Shoreview, MN) and DustTrak DRX 8533 (TSI Inc., 500 Cardigan Road Shoreview, MN) as portable real-time monitors for measuring PM2.5 concentrations and compared these values with those measured with the PMS-103 or SEQ 47/50 models operated by Federal Reference Method (FRM) or the European Committee for Standardization(ECS), respectively, in national urban air-quality monitoring sites in Seoul. Measurements were conducted every other day in the winter and spring seasons of 2014. The estimated daily mean concentrations of PM2.5 ranged between 13.4 and 161.9 μg/m3 using AM 510 and between 22.0 and 156.0 μg/m3 using DustTrak. The Spearman correlation coefficient for PM2.5 concentrations between AM 510 and gravimetric results was 0.99, and the correlation between DustTrak and gravimetric results was 0.87. The correction factor suggested was 0.42 and 0.29 for AM 510 and DustTrak, respectively. We found that PM2.5 concentrations measured with real-time monitors could overestimate true PM2.5 concentrations and therefore the application of a correction factor (0.43) is strongly suggested for quantification when Real-time monitors were operated of PM2.5 levels at urban atmospheric environment of South Korea.

Abstract
 1. Introduction
 2. Material and methods
  2.1. PM2.5 measurement devices
  2.2. Measurement of PM2.5 concentrations
  2.3. Data analysis
 3. Results and Discussions
  3.1. PM2.5 concentration levels
  3.2. Ratio of PM2.5 concentrations by RT to G(RT/G) methods
  3.3. Correction factors for PM2.5 for RT monitors
 4. Conclusions
 REFERENCES

• Sung-Roul Kim(Department of Environmental Health Sciences, Soonchunhyang University) Corresponding author
• Sol Yu(APM Engineering)
• Seon-Yeub Lee(Department of Environmental Health Sciences, Soonchunhyang University)
• Dong-Jae Lee(Department of Environmental Health Sciences, Soonchunhyang University)
• Bo-Kyeong Kim(Department of Environmental Health Sciences, Soonchunhyang University)
• Jun-Bok Lee(Seoul Metropolitan Government Research Institute of Public Health and Environment)
• Myeong-Bok Kim(APM Engineering)
• Dong-Min Yun(Department of Environmental Health Sciences, Soonchunhyang University)