Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-AS Atmospheric Sciences, Meteorology & Atmospheric Environment

[A-AS04] Atmospheric Chemistry

Thu. May 30, 2019 10:45 AM - 12:15 PM 102 (1F)

convener:Tomoki Nakayama(Graduate School of Fisheries and Environmental Sciences, Nagasaki University), Yoko Iwamoto(Graduate School of Biosphere Science, Hiroshima University), Sakae Toyoda(Department of Chemical Science and Engineering, Tokyo Institute of Technology), Nawo Eguchi(Kyushu University), Chairperson:Fumikazu Taketani(海洋研究開発機構), Michihiro Mochida(名古屋大学)

11:30 AM - 11:45 AM

[AAS04-25] Sensitivity of regional deposition of inhaled atmospheric aerosols in human respiratory tract to their size distribution and hygroscopicity: A case study

*Minrui Wang1, Toshiyuki Mihara2,4, Mizuo Kajino5, Kaori Kawana2,6, Michihiro Mochida1,2,3 (1.Institute for Space Earth Environmental Research, 2.Graduate School of Environmental Studies, Nagoya University, 3.Institute for Advanced Research, Nagoya University, 4.Now at Gifu Prefectural Industrial Research Institute, 5.Meteorological Research Institute, Japan Meteorological Agency, 6.Now at Research and Development Center for Global Change, JAMASTEC)

Keywords:Aerosol, size distribution, hygroscopicity, regional deposition

Aerosols, which inhaled to human respiratory tract, can cause various diseases that threaten one’s health. In order to estimate aerosol’s health risk, it is significant to elucidate the sensitivity of regional deposition of inhaled aerosols.

In this study, by applying size distribution and hygroscopic growth factor data of aerosol (measured by a scanning mobility particle sizer in September 2009 and July-August 2010) to an MPPD (Multiple-Path Particle Dosimetry) model, we calculated the regional deposition differentiated by size diameter/hygroscopicity for a resting/light exercising adult male. As a result, regional deposition ratio in intrathoracic region (both tracheobronchial airway and alveolar interstitium) showed a bimodal distribution among particle size diameter ranging between 24.1~359.0 nm, in which the maximum value was 50.1%/50.0% at 24.1 nm (during light exercise). In general, there was a decreasing trend in deposition ratio when particle size diameter increased. For mode particles (dry diameter dp,dry < 100 nm), the regional deposition of particles that have low hygroscopicity parameter (κ) tent to be larger than those with higher κ. However, for larger particles (especially when dp,dry > 200 nm), this trend became reversed.

In 2009 the measurement was continuous for 10 days, while daily variation was found in aerosol number-size distribution and regional deposition. Therefore, we analyzed the meteorological data of the measurement period in 2009, comparing daytime (12:00-18:00 LST) and nighttime (00:00-06:00 LST) in order to indicate meteorological matters that affect the temporal variation of regional deposition. The result showed that the relative humidity (RH) during daytime was basically lower than 50% except September 15 and September 22~23 due to continuous rain, and the distribution of regional deposition was maximum for relatively hydrophobic mode particles (dp,dry < 100 nm, hygroscopic growth factor g ranges between 1.0~1.2). On the other hand, RH during nighttime was mostly higher than 60%, and a bimodal distribution of both hydrophobic and hydrophilic (g ranges between 1.2~1.4) particles was found. Meanwhile, on September 23 RH was high (over 75%) during whole day, we found a monomodal distribution of regional deposition with a maximum value for hydrophilic particles that last about 6 hours in the afternoon.

According to our results we suggested that along with the temporal variation of artificial emission, changes in ambient humidity could also influence the composition of inhaled aerosol particles to a great extent, and therefore affected the regional deposition.