三宅島起源硫酸エアロゾルにより気相に追い出された硝酸・塩酸による酸性沈着の増加

Abstract

三宅島火山の噴火に伴い増加した火山性硫酸により，エアロゾル中の硝酸塩や塩酸塩が気相に追い出されていた。追い出された硝酸ガス・塩酸ガスの沈着速度は，硝酸塩・塩酸塩のそれと比べて非常に大きいので，噴火の影響で硝酸・塩酸による酸性沈着が増加したと考えられる。この二次的（追加的）な酸性化効果を，火山性硫酸塩がそのまま沈着する直接的な酸性化に対して，「間接的環境酸性化」効果と名付け，それをエアロゾル化学輸送モデルにより初めて定量的に評価した。

The eruption of Miyakejima Volcano has resulted in the emission of large amounts of sulfur dioxide. The volumes of sulfur dioxide emitted were vast. Short-time aerosol sampling, conducted at the Happo Ridge, has revealed that the abundant volcanic sulfate resulted in the expulsion of non-volcanic nitrate and chloride in aerosols into the gas phase. As the deposition velocities of gaseous nitrate and chloride are much higher than those in aerosols, the deposition of them should be accelerated. This additional deposition is referred to as ""indirect acidification"" in this study, corresponding to ""direct acidification"" by the deposition of volcanic sulfate. This indirect acidification is estimated quantitatively using a regional-scale Eulerian aerosol transport model.