VERIFICATION OF ACCURACY OF CO₂ PARTIAL PRESSURE ESTIMATION AND LONG-TERM CHANGES IN CO₂ ABSORPTION CAPACITY IN OSAKA BAY

Abstract

 No examples of seawater CO₂ partial pressure observed over time in Osaka Bay, so it is necessary to estimate CO₂ partial pressure from TA, pH, and DIC based on the carbonic acid equilibrium relationship to understand long-term changes in the CO₂ absorption capacity of the bay area. In this study, seawater samples were collected from the coasts of Osaka Bay to verify the accuracy of CO₂ partial pressure estimation, and the CO₂ absorption capacity of Osaka Bay since the 1980s was determined from environmental statistical data. Comparison of the estimated values obtained by varying the combination of observed variables and the dissociation constant model with the measured values showed that the accuracy of estimates using TA decreased by up to 12% in estuarine areas affected by urban drainage, and the estimated values varied by up to 5.6% depending on the dissociation constant used for the same seawater. On the other hand, the overall CO₂ absorption capacity of Osaka Bay is increasing, not only in the inner part of the bay, which is known to have a high absorption capacity, but also at the mouth of the bay.