Characterization of atmospheric air pollutants through a long-range transport from the Asian continent to northern Kyushu in Japan : Acidity and chemical form of particulate matter and chemical reaction(Atmospheric Environment and Cultural Properties)

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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 200km 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 island 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 transpot 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 the sea west of Kyushu and Goto Island, were transported to island 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 west of Kyushu.
社団法人大気環境学会の論文
2001-10-06

Characterization of atmospheric air pollutants through a long-range transport from the Asian continent to northern Kyushu in Japan : Acidity and chemical form of particulate matter and chemical reaction(Atmospheric Environment and Cultural Properties)

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