Bich-Thuy Ly 1,2, Yutaka Matsumi 2, Tomoki Nakayama2,3, Yosuke Sakamoto4,5,6, Yoshizumi Kajii4,5,6, Trung-Dung Nghiem1

School of Environmental Science and Technology, Hanoi University of Science and Technology, Hanoi, Vietnam\
Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Aichi 464-8601, Japan
Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Nagasaki, Nagasaki 852-8521, Japan
Graduate School of Global Environmental Studies, Kyoto University, Kyoto, Kyoto 606-8501, Japan
Graduate School of Human and Environmental Studies, Kyoto, Kyoto 606-8501, Japan
Center for Regional Environmental Research, National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan

Received: December 13, 2017
Revised: April 27, 2018
Accepted: April 27, 2018
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Cite this article:
Ly, B.T., Matsumi, Y., Nakayama, T., Sakamoto, Y., Kajii, Y. and Nghiem, T.D. (2018). Characterizing PM2.5 in Hanoi with New High Temporal Resolution Sensor. Aerosol Air Qual. Res. 18: 2487-2497.


  • Observation of PM2.5 was conducted using high temporal resolution sensors in Hanoi.
  • Hourly PM2.5 mass concentrations by the sensor agreed with those by a BAM instrument.
  • PM2.5 levels were high in dry season (winter) and low in rainy season (summer).
  • PM2.5 haze episodes were observed, especially several days after a cold surge.
  • This research reveals for first time characteristics of PM2.5 haze episode in Hanoi.


A year-long observation of PM2.5 concentrations was conducted in Hanoi from July 2016 to June 2017 using newly developed highly sensitive sensors. The hourly concentration data of PM2.5 agreed well with corresponding data obtained with a beta attenuation monitor located 3 km away, with R2 = 0.73. The monthly variation showed that levels of PM2.5 were high during the dry season, particularly in December (median = 62 µg m–3) and low during the rainy season, particularly in June and July (medians = 19 µg m–3). Haze episodes of PM2.5 with levels higher than 100 µg m–3 were observed 13 times during the dry season (October 2016–March 2017). These episodes may be linked to the East Asian winter monsoon, as the daily levels of PM2.5 and CO increased several days after most of the cold surge events. Two events were investigated further at a higher temporal resolution. For both events, peaks of PM2.5 appeared at midnight for some days after a cold surge, while CO levels often increased during rush hours. For the first event, brief peaks of PM2.5 with a high rate of increase (~5 µg m–3 min–1) were observed, highlighting the importance of a high temporal resolution for PM2.5 sensors in assessing health effects. For the second event, a broad peak of PM2.5 with a gradual increase was observed along with high CO levels. This research reveals the characteristics of PM2.5 haze episodes in Hanoi, which should be studied further to effectively manage air pollution.

Keywords: PM2.5 measurement; Compact sensor; Megacity; Southeast Asia.


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