Modeling the impact of CO 2 releases in Kagoshima Bay, Japan

A model is developed to simulate CO2 gas releases from moderate ocean depths. It can simulate CO2 releases from a single point, or releases spread over an area (non-point source). The model uses multi-species Lagrangian parcels approach to model CO2 in both gas and dissolved gas phases (i.e. the changes in the gas released as well as the changes in the ambient water caused by the dissolved gas). The physico-chemical processes included are: gas expansion during upward travel due to pressure changes; gas dissolution and its impact on bubble volume; continuous recalculation of bubble buoyant velocity based on the volume and density changes; and tracking the transport and dispersion of dissolved and free gas. The buoyant velocity and dissolution computations take the non-circular nature of the bubble into consideration. The Model calculates dissolved CO2 concentration, pH, and TCO2 in water. The model is used to calculate and compare the changes in pH values due to natural CO2 releases in Kagoshima Bay, Japan. The comparisons are reasonably good. The results show that pH value in seawater can change slightly after many hours of release for the cases considered.