ヘマタイト粒子と硫酸エアロゾルの反応による鉄イオン溶出速度の定量化

抄録

In the ocean, iron in a soluble form acts as a micronutrient for oceanic phytoplankton. Mineral dust deposition to the ocean may be a significant source of iron that is typically insoluble. It is required to understand the atmospheric processes that convert insoluble iron to soluble forms. We focused attention on Fe-leaching from hematite particles when they come into direct contact with sulfuric acid aerosols, and performed laboratory experiments to determine their dissolved fraction to ferric ion and the temperature dependence of the dissolution rate. Hematite particles ranging from 2.1 to 3.3 μm in aerodynamic diameter were prepared using a nebulizer combined with classification by a cascade impactor, and sulfuric aerosols (0.5 μm, pH 0) were generated with an ultrasonic nebulizer. Reactions between the hematite particles and the sulfuric acid mists were conducted at 40 % R.H. under 15-25 °C over a range of reaction time from 24 hr to 72 hr. Hematite dissolution was accelerated with an increase of reaction temperature and the dissolved fraction was 0.82 % at 15 °C after 72 hr reaction, which was comparable to the previous theoretical estimates. We also determined the temperature dependence of the dissolution rate, and derived the Arrhenius rate equations.