Characterization of atmospheric air pollutants at two sites in northern Kyushu, JapanAchemical form, and chemical reaction

• Published in: Atmospheric environment (1994) Vol. 35; no. 4; pp. 667 - 681
• Main Authors: Shimohara, Takaaki, Oishi, Okihiro, Utsunomiya, Akira, Mukai, Hitoshi, Hatakeyama, Shiro, Eun-Suk, Jang, Uno, Itsushi, Murano, Kentaro
• Format: Journal Article
• Language: English
• Published: 01.01.2001
• Subjects: Kyushu, Japan
• ISSN: 1352-2310

Airborne gaseous and particulate matter in winter was measured for over 37 days in January and December 1997 at 2 sampling sites in northern Kyushu, Japan. One sampling site, Goto Island (an isolated island in the East China Sea), was about 200 km southwest of the other sampling site, Dazaifu city. In winter, acidic sulfates generated over the East Asian continent were transported to northwest Kyushu, to places such as Goto Island and the inland Kyushu area, and high sulfate concentrations were observed at the 2 sampling sites when strong NW winds blew. Acidity around Goto was mainly influenced by particulate NH sub(4) HSO sub(4) . The concentrations of NH sub(3) at Goto Island were lower than at Dazaifu city. The difference in NH sub(3) levels at the 2 sampling sites plays an important role in the chemical forms and sizes of the particulate matter. Nitrates at Goto Island were mostly present as NaNO sub(3) and Ca(NO sub(3) ) sub(2) in coarse-size particles. During the process of long-range transport of air pollutants from the Asian continent to Goto, gaseous HNO sub(3) was produced by a photochemical reaction of nitrogen oxides in the atmosphere, and particulate NaNO sub(3) and gaseous HCl were formed by a chlorine-loss reaction between NaCl and gaseous HNO sub(3) . When strong NW winds blew, acidic sulfates together with some of the NaNO sub(3) and/or Ca(NO sub(3) ) sub(2) and some of gaseous HCl and HNO sub(3) , which exist in the sea to the west of Kyushu and Goto Island, were transported to inland Kyushu such as Dazaifu city. During the process of transport, most of the acidic sulfates and acidic gases were mixed with regional air pollutants such as chlorides and nitrates existing around Dazaifu city, and neutralized forming (NH sub(4) ) sub(2) SO sub(4) , NH sub(4) Cl and NH sub(4) NO sub(3) in an environment of excess NH sub(3) . Therefore, the main chemical forms of NO sub(3) super(-) at Dazaifu city varied day-by-day from fine-sized NH sub(4) NO sub(3) to coarse-sized NaNO sub(3) and/or Ca(NO sub(3) ) sub(2) . The appearance of NO sub(3) super(-) in coarse-size particles at Dazaifu city was due to the transport of NO sub(3) super(-) from around the sea to the west of Kyushu.