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

Elsevier Ltd
Publication Date
DOI: 10.1016/s1352-2310(00)00340-x
  • Acidic Aerosols
  • Sulfate
  • Nitrate
  • Winter Monsoon
  • Long-Range Transport Model
  • Chlorine-Loss Reaction
  • Chemistry


Abstract Airborne gaseous and particulate matter in winter was measured over for 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 4HSO 4. The concentrations of NH 3 at Goto Island were lower than at Dazaifu city. The difference in NH 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 3 and Ca(NO 3) 2 in coarse-size particles. During the process of long-range transport of air pollutants from the Asian continent to Goto, gaseous HNO 3 was produced by a photochemical reactions of nitrogen oxides in the atmosphere, and particulate NaNO 3 and gaseous HCl were formed by a chlorine-loss reaction between NaCl and gaseous HNO 3. When strong NW winds blew, acidic sulfates together with some of the NaNO 3 and/or Ca(NO 3) 2 and some of gaseous HCl and HNO 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 4) 2SO 4, NH 4Cl and NH 4NO 3 in an environment of excess NH 3. Therefore, the main chemical forms of NO 3 − at Dazaifu city varied day-by-day from fine-sized NH 4NO 3 to coarse-sized NaNO 3 and/or Ca(NO 3) 2. The appearance of NO 3 − in coarse-size particles at Dazaifu city was due to the transport of NO 3 − from around the sea to the west of Kyushu.

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