Elevated Levels of Particulate Sulfate in Central Japan due to Volcanic Gas from Miyake Island.

概要

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Elevated concentrations of sulfur dioxide (SO2) exceeding the environmental standard were observed in Nagano Prefecture as well as in the Kanto and Tokai areas of Japan in August and September 2000, prompting many residents to complain of the offensive smell. Maximum concentrations of 383 ppb SO2 at Iida (in the south of the prefecture) and 76 ppb SO2 at Nagano (in the north of the prefecture) were observed. Backward trajectory analysis suggested the source to be volcanic gas from Miyake Island, whose volcanic activity has dramatically intensified recently. Measurements of gases and aerosols by a four-stage filter pack method were made at Nagano, Mt. Happo, and the village of Hakuba in the north of Nagano prefecture. The concentration of SO42- in aerosols was extremely high at 44.4 μg/m3 in Nagano on September 14, and on September 15 it exceeded 30 μg/m3 at both Mt. Happo and Hakuba. On the basis of the assumed ion balance of SO42- and NH4+, unusually high levels of sulfuric acid (H2SO4) and high molar concentration ratios for H2SO4/SO42- were estimated for each of the 3 locations: H2SO4 concentrations were 21-33 (Nagano), 11-21 (Mt. Happo), and 6.8-18μg/m3 (Hakuba); molar concentration ratios were 46%-2%, 34%-5%, and 22%-58%.
社団法人大気環境学会の論文