Morphological and chemical composition characteristics of summertime atmospheric particles collected at Tokchok Island, Korea Hong Geng a , Hae-Jin Jung a , YooMyung Park a , HeeJin Hwang b , HyeKyeong Kim a , Yoo Jung Kim c , Young Sunwoo d , Chul-Un Ro a, * a Department of Chemistry, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751, Republic of Korea b Korea Polar Research Institute, Incheon 406-840, Republic of Korea c Department of Environmental Engineering, Konkuk University, Seoul 143-701, Republic of Korea d Department of Advanced Technology Fusion, Konkuk University, Seoul 143-701, Republic of Korea article info Article history: Received 8 November 2008 Received in revised form 24 March 2009 Accepted 25 March 2009 Keywords: Low-Z particle EPMA Single-particle analysis Morphology Chemical composition Tokchok Island abstract Determination of the chemical compositions of atmospheric single particles in the Yellow Sea region is critical for evaluating the environmental impact caused by air pollutants emitted from mainland China and the Korean peninsula. After ambient aerosol particles were collected by the Dekati PM10 cascade impactor on July 17–23, 2007 at Tokchok Island (approximately 50 km west of the Korean coast nearby Seoul), Korea, overall 2000 particles (on stage 2 and 3 with cut-off diameters of 2.5–10 mm and 1.0– 2.5 mm, respectively) in 10 samples were determined by using low-Z particle electron probe X-ray microanalysis. X-ray spectral and secondary electron image (SEI) data showed that soil-derived and sea- salt particles which had reacted or were mixed with SO 2 and NO x (or their acidic products) outnumbered the primary and ‘‘genuine’’ ones (59.2% vs. 19.2% in the stage 2 fraction and 41.3% vs. 9.9% in the stage 3 fraction). Moreover, particles containing nitrate in the secondary soil-derived species greatly out- numbered those containing sulfate. Organic particles, mainly consisting of marine biogenic species, were more abundant in the stage 2 fraction than in the stage 3 fraction (11.6% vs. 5.1%). Their relative abun- dance was greater than the sum of carbon-rich, K-containing, Fe-containing, and fly ash particles, which exhibited low frequencies in all the samples. In addition, many droplets rich in C, N, O, and S were observed. They tended to be small, exhibiting a dark round shape on SEI, and generally included 8–20 at.% C, 0–12 at.% N, 60–80 at.% O, and 4–10 at.% S (sometimes with <3 at.% Mg and Na). They were attributed to be a mixture of carbonaceous matter, H 2 SO 4 , and NH 4 HSO 4 /(NH 4 ) 2 SO 4 , mostly from the reaction of atmospheric SO 2 with NH 3 under high relative humidity. The analysis of the relationship between the aerosol particle compositions and 72-h backward air-mass trajectories suggests that ambient aerosols at Tokchok Island are strongly affected not only by seawater from the Yellow Sea but also by anthropogenic pollutants emitted from China and the Seoul–Incheon metropolis, resulting in the dominance of complex secondary aerosol particles. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction The Yellow Sea is surrounded by rapidly industrializing and urbanizing areas of Korea and China. A large number of land-source materials and pollutants can be atmospherically transported over it, especially anthropogenic SO 2 and NO x which are emitted from both sides. Many studies reported that these sulfur and nitrogen oxide species, mostly emitted from the power plants, vehicles, domestic heating, and industrial sources (Chan and Yao, 2008), can enhance the production of particulate sulfate and nitrate on the surface of dust particles in the marine atmosphere and over the Korean peninsula in winter and spring times during which Asian dust frequently occurs and the emission of anthropogenic SO 2 and NO x is larger (Jeong and Park, 2008; Hwang and Ro, 2005). But few studies, especially by single-particle analysis, were conducted to investigate how they exert great influence on the airborne particle composition in summertime when temperature and relative humidity are relatively high, Asian dust scarcely occurs, and ambient fine particle (PM 2.5 ) mass concentrations are lower (related to the large amounts of wet deposition in the summer). Herein, Tokchok Island, Korea, in the Yellow Sea nearby Seoul– Incheon metropolis, was selected as our sampling site to investigate * Corresponding author. Tel.: þ82 32 860 7676; fax: þ82 32 867 5604. E-mail address: curo@inha.ac.kr (C.-U. Ro). Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2009.03.034 Atmospheric Environment 43 (2009) 3364–3373