Emission of carbon dioxide from a tropical estuarine system, Goa, India

Abstract

Carbon dioxide species were studied in Mandovi-Zuari system, a tropical estuarine complex influenced by strong monsoonal run-off, with implications to build up and air-water exchange of CO₂. Total carbon dioxide (TCO₂) behaved conservatively during the estuarine mixing. Partial pressure of carbon dioxide (pCO₂), evaluated from TCO₂ and pH couple, and carbonic acid dissociation constants, exhibited supersaturation with respect to atmospheric CO₂ round the year. The pCO₂ attained maximal levels over 2000 µatm in waters of early estuarine mixing. Average pCO₂ in estuarine system were 1045 and 1153, µatm (three times to that in atmosphere) in non- southwest (SW) and SW monsoon seasons, respectively. An experimental study revealed that soil-water interaction could be an important controller of pCO₂ abundance in these estuarine waters. The calculated water-to-air average fluxes were 67 and 11 mmol m^-2 d^-1, respectively, in SW monsoon due to higher wind speeds and non-SW monsoons. This study strongly suggests that pH regulation by soil-water interaction is important, besides biological processes, in river and estuarine systems.