AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Elucidation of the Influence of Specific Meteorological Conditions on the Electrostatic Charging State of Ambient Aerosols by a Parallel Electrode Plate Device
RYOYA TABATA, Ayumi Iwata, Kentaro Fujioka, Tomoaki Okuda, Keio University
Abstract Number: 167 Working Group: Aerosol Chemistry
Abstract In recent years, the influence on health by fine aerosol particles such as PM2.5 has been concerned. Especially regarding the particle deposition in a human airway, some previous studies show that the deposition rate of charged particles to airway surface is several times higher than that of uncharged particles. However, little knowledge on the electrostatic charging state of atmospheric aerosols has been obtained so far. Therefore the electrostatic charging state of atmospheric aerosols has been measured since April 2017 using a parallel electrode plate device utilizing the principle of electric mobility. We call this device K-MACS (Keio-Measurement System of Aerosol Charging State). The flow path of K-MACS is divided into three, and when +1.5 kV is applied, uncharged particles come out from the middle exit. Therefore we compare the number concentration of particles coming out from the middle exit with that of the inlet and calculate the proportion of uncharged particles.
The results varied depending on the measurement day, and the proportion of uncharged particles was about 12-25%. By investigating the relationship between the electrostatic charging state and the meteorological condition at the time of measurement, there was a strong positive correlation between the proportion of uncharged particles and the volumetric humidity. To investigate the relationship between the proportion of uncharged particles and the volumetric humidity, we measured the electrostatic charging state while the volumetric humidity was manually changed. When a continuous measurement of the uncharged particles proportion was conducted at sunny weather condition, there was a strong positive correlation between the proportion of uncharged particles and the oxidant concentration. As a factor of correlation, we thought that secondary generated particles influenced the electrostatic charging state of ambient aerosols. Therefore, we simultaneously measured the electrostatic charged state, Aitken particles, and the atmospheric ion concentration.