Metropolitan Tokyo area in Japan suffered from a strong Asian dust event which was lasted for 3 days from May 6 to May 8 in 2017. Asian dust particles are usually originated from the deserts of Mongolia and Kazakhstan and could be absorbed air pollutants contained the metals, water-soluble and organic matters during transport process. In this research, two sampling sites called 10F (30m height above ground level) and roadside in Saitama were selected to collect five different size particles (PM1.1, PM1.1–2.0, PM2.0–3.3, PM3.3–7.0 and the coarse particles (>7.0 μm) of three different events: (1) before Asian dust event (B.A.), (2) during Asian dust event (D.A.) and (3) after Asian dust event (A.A.). Eight watersoluble ionic and 23 elemental species in D.A. event were higher than other periods. In D.A. event, the ionic contents in 10F were high to 10.3 μg/m3 and the elemental contents in roadside were 6.50 μg/m3 which were higher than those in roadside. Ionic contents were mainly distributed in PM1.1 with the high contents of secondary particles (NH4+, NO3− and SO42−). Ca2+, Cl− and Na+ were more enriched in the coarse particles. Ion balance in D.A. event was more basic in 10F and more acidic in roadside. The higher ratios of NO3−/SO42− in PM1.1 were also occurred in D.A. event. Total elements were high (6,050 ng/m3) in 10F with the several times increasing in PM3.3–7.0 and the coarse particles, and the great contribution form the crustal elements (Al, Fe, Na, Mg and K). Enrichment factors (EFs) of trace elements in PM1.1 indicating the anthropogenic sources might be the main sources of those ions. EFs in the coarse particles indicating high concentrations of crustal elements might be affected by the Asian dust event. The analysis of air masses backward trajectories showed that the deserts of Mongolia and Kazakhstan and the northern part of China were the important air pollutant origins in Asian dust events with long-distance transport.
Asian dust, metal elements, Saitama, water-soluble inorganic ions
 Japan Meteorological Agency, https://www.jma.go.jp/jma/menu/menureport.html
 Otani, Shinji, et al., Dust storms from degraded drylands of Asia: dynamics and health impacts. Land, 6(4), p. 83, 2017.
 Shimizu, Atsushi, et al., Variations of Dust Extinction Coefficient Estimated by Lidar Observations over Japan, 2007–2016. SOLA, 13, pp. 205–208, 2017.
 Kanatani, Kumiko T., et al., Effect of desert dust exposure on allergic symptoms: a natural experiment in Japan. Annals of Allergy, Asthma & Immunology, 116(5), pp. 425–430, 2016.
 A, Wang, Qingyue, et al. Size-segregated Allergenic Particles Released from Airborne Cryptomeria japonica Pollen Grains during the Yellow Sand Events within the Pollen Scattering Seasons. Asian Journal of Atmospheric Environment (AJAE), 7(4), pp.191–198, 2013.
 Watanabe, Masanari, et al., Correlation between Asian dust storms and worsening asthma in Western Japan. Allergology International, 60(3), pp. 267–275, 2011.
 Dias, G.M., Differentiating natural and anthropogenic sources of metals to the environment. Human and Ecological Risk Assessment, 9(4), pp. 699–721, 2003.
 Tsai, Y.I., Characterization of Asian dust storm and non-Asian dust storm PM2.5 aerosol in southern Taiwan. Atmospheric Environment, 40(25), pp. 4734–4750, 2006.
 Saitama Prefecture air pollution continuous monitoring system, http://www.taiki-kansi.pref.saitama.lg.jp/
 Wang, qingyue & Weiqian, Wang, Survey of inorganic components in atmospheric particles of three urban areas caused by winter energy consumption in China and Japan. WIT Transactions on Ecology and the Environment, 217, pp. 469–479, 2018.
 Squizzato, S., et al., Factors determining the formation of secondary inorganic aerosol: a case study in the Po Valley (Italy). Atmospheric chemistry and physics, 13(4), pp. 1927–1939, 2013.
 Zhang, Yy., Chemical characteristics of PM2.5 during 2015 spring festival in Beijing, China. Aerosol and Air Quality Research , 17(5), pp. 1169–1180, 2017.
 Wang, Y., The variation of characteristics and formation mechanisms of aerosols in dust, haze, and clear days in Beijing. Atmospheric Environment, 40(34), pp. 6579–6591, 2006.
 Tan, J-H., Source of atmospheric heavy metals in winter in Foshan, China. Science of the Total Environment, 493, pp. 262–270, 2014.
 Bilos, C., Sources, distribution and variability of airborne trace metals in La Plata City area, Argentina. Environmental pollution, 111(1), p. 1, 2001.
 Arditsoglou, A., Levels of total suspended particulate matter and major trace elements in Kosovo: a source identification and apportionment study. Chemosphere, 59(5), pp. 669–678, 2005.