Poster

IAMAS

M02 - Atmospheric Composition and the Asian Monsoon

Organic functional groups and other chemical components in atmospheric aerosols in Nagoya and Osaka, Japan: Results from a field study in February and March, 2024

Although decreasing trends of the concentrations of atmospheric fine aerosols were reported for East Asian countries, to understand the temporal and spatial variations of the abundances and composition of aerosols are still vital for assessing their environmental impacts and finding appropriate measures to mitigate pollutions. In particular, the mechanisms that govern the abundances and composition of organic components were still not clear, and the characterization of organic aerosol by field studies is expected to provide evidence to advance our knowledge. In this study, we performed an intensive field study for atmospheric aerosols in two cities in Japan, Nagoya and Osaka, and characterized the aerosol chemical components including organic functional groups (OFGs). Aerosol samples were collected on Higashiyama Campus, Nagoya University in Nagoya and in Osaka City Research Center of Environmental Science, Osaka, in the period from February 22 to March 23, 2024. PM2.5 samples collected on PTFE filters were subjected to infrared transmission spectroscopy for the analysis of OFGs. An FTIR instrument with a home-made filter holder was used for this OFG analysis. The quantification of OFGs based on the collected FTIR spectra were performed using AIRSpec software. PM2.5 samples collected on quartz fiber filters were used for the analysis of water-soluble organic carbon (WSOC) and water-soluble ions, which were respectively measured using a total organic carbon analyzer and an ion chromatograph. Aerosol size distributions in Nagoya were also obtained by in-situ measurements. In Nagoya, the FTIR-derived mass concentrations of organic matter (OM) were 4.2 �� 3.1 microgram m?3, whereas the concentrations of WSOC and sulfate (for similar sampling durations) were 1.3 �� 0.8 and 1.4 �� 1.0 microgram m?3, respectively. In the case of Osaka, the concentrations of OM were 3.4 �� 2.9 microgram m?3, whereas those of WSOC and sulfate were 1.4 �� 0.9 and 1.9 �� 1.2 microgram m?3, respectively. The OM/OC mass ratios for Nagoya were estimated to be 2.0 �� 0.1 (for >1 microgram m?3 OM concentration). The calculated OM/OC for Osaka may be unrealistic (2.4 �� 0.6, for >1 microgram m?3 OM concentration), presumably because of low aerosol loading per area as a result of relatively large sampling area on the filters. Nevertheless, positive correlation (r = 0.79) was observed between OM concentrations from two cities; a possible reasons of the harmonized variations is the influence of the regional transport of aerosols. For Nagoya, the concentrations of OFGs and their relative abundances are 1.7 �� 1.3, 1.5 �� 1.2, 0.6 �� 0.4, 0.3 �� 0.2, and 0.1 �� 0.2 microgram m?3 for alkane CH, carboxylic COOH, alcohol COH, amine NH, and non-acid CO groups, respectively. The concentrations of oxygen atoms in OM in Nagoya (2.1 �� 1.5 microgram m?3) were comparable to those of sulfate. Although the measurement uncertainty should be assessed, the result suggests the importance of oxygenation of organic components to aerosol mass concentrations. The results from the present FTIR analysis are expected to support further characterization of the studied samples by alternate approaches, including an offline use of an aerosol mass spectrometer.