The pH Distribution During CO2 Dissolving Into Water Under Mid-Depth Sea Condition

Sequestration of liquid CO2 into the intermediate depth ocean has been considered as a means to reduce atmospheric concentration of this greenhouse gas and mitigate global warming. A number of CO2 droplets are released and diluted into the intermediate ocean. The behavior of CO2 dissolution is very important in order to control the concentration of CO2 and to keep the environmental impact minimum. Under conditions in the intermediate ocean, that is, high pressure and low temperature, the CO2 clathrate hydrate film was formed on the CO2 droplet surface. The hydrate film has been considered to decrease the dissolution rate and the CO2 concentration near the droplet surface. The authors applied a LIF technique with a new kind of the dye as a pH indicator. The new dye in the CO2 dissolved water emitted intense fluorescence dependent on its pH. The visualized images showed the two dimensional distribution of the pH, i.e., CO2 concentration, around the CO2 droplet with or without the hydrate film.