Offline analysis of the chemical composition and hygroscopicity of sub-micrometer aerosol at an Asian outflow receptor site and comparison with online measurements
- 1Graduate School of Environmental Studies, Nagoya University, Nagoya, 464-8601, Japan
- 2Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, 464-8601, Japan
- 3Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, 183-8538, Japan
- 4Institute of Low Temperature Science, Hokkaido University, Sapporo, 060-0819, Japan
- 5Chubu Institute for Advanced Studies, Chubu University, Kasugai, Aichi, 487-8501, Japan
- 6School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, Guangdong, 519082, China
- 7Institute of Tropical and Marine Meteorology, China Meteorological Administration, Guangzhou, 510-640, China
- 8Department of Earth and Planetary Science, The University of Tokyo, Tokyo, 113-8654, Japan
- 9National Institute of Polar Research, Tokyo, 190-8518, Japan
- 10National Institute for Environmental Studies, Tsukuba, 305-8506, Japan
- anow at: National Institute for Environmental Studies, Tsukuba, 305-8506, Japan
- bnow at: Department of Chemistry, Biology, and Marine Science, University of the Ryukyus, Okinawa, 903-0213, Japan
- cnow at: Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Nagasaki, 852-8521, Japan
- dnow at: Institute for Environmental and Climate Research, Jinan University, Guangzhou, Guangdong, 511443, China
- enow at: Xiamen Key Laboratory of Straits Meteorology, Xiamen Meteorological Bureau, Xiamen, 361012, China
- fnow at: Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, 464-8601, Japan
- gnow at: Institute for Advanced Research, Nagoya University, Nagoya, 464-8601, Japan
- hnow at: Asia Center for Air Pollution, Japan Environmental Sanitation Center, Niigata, 950-2144, Japan
Abstract. Filter-based offline analysis of atmospheric aerosol hygroscopicity coupled to composition analysis provides information complementary to that obtained from online analysis. However, its application itself and comparison to online analysis have remained limited to date. In this study, daily submicrometer aerosol particles (PM0.95, 50 % cutoff diameter: 0.95 μm) were collected onto quartz fiber filters in Okinawa Island, a receptor of East Asian outflow, in the autumn of 2015. The chemical composition of water-soluble matter (WSM) in PM0.95 and PM0.95 itself, and their respective hygroscopicities were characterized through the offline use of an aerosol mass spectrometer and a hygroscopicity tandem differential mobility analyzer. Thereafter, results were compared with those obtained from online analyses. Sulfate dominated the WSM mass (60 %), followed by water-soluble organic matter (WSOM, 20 %) and ammonium (13 %). WSOM accounted for most (93 %) of the mass of extracted organic matter (EOM) and the atomic O to C ratios (O : C) of WSOM and EOM were high (mean ± standard deviation were, respectively, 0.84 ± 0.08 and 0.79 ± 0.08), both of which indicate highly aged characteristics of the observed aerosol. The hygroscopic growth curves showed clear hysteresis for most samples. At 85 % RH, the calculated hygroscopicity parameter κ of the WSM (κWSM), WSOM, EOM, and PM0.95 (κPM0.95) were, respectively, 0.50 ± 0.03, 0.22 ± 0.12, 0.20 ± 0.11, and 0.47 ± 0.03. An analysis using the thermodynamic E-AIM model shows, on average, that inorganic salts and WSOM respectively contributed 88 % and 12 % of the κWSM (or κPM0.95). High similarities were found between offline and online analysis for chemical compositions that are related to particle hygroscopicity (the mass fractions and O : C of organics, and the degree of neutralization), and also for aerosol hygroscopicity. As possible factors governing the variation of κWSM, the influences of WSOM abundance and the neutralization of inorganic salts were assessed. At high RH (70–90 %), the hygroscopicity of WSM and PM0.95 was affected considerably by the presence of organic components; at low RH (20–50 %), the degree of neutralization could be important. This study not only characterized aerosol hygroscopicity at the receptor site of East Asian outflow, but also shows that the offline hygroscopicity analysis is an appropriate method, at least for aerosols of the studied type. The results encourage further applications to other environments and to more in-depth hygroscopicity analysis, in particular for organic fractions.
Yange Deng et al.
Status: open (until 02 Dec 2021)
Yange Deng et al.
Yange Deng et al.
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