Inorganic carbon dynamic and air–water CO2 exchange in the Guadalquivir Estuary (SW Iberian Peninsula)

The distribution of inorganic carbon and the CO2 exchange between atmosphere and water along the Guadalquivir Estuary (SW Iberian Peninsula) have been evaluated, on the basis of field observation performed from 2000 to 2003. The study consisted of the measurement of Total Alkalinity (TAlk), pH, continuous underway CO2 partial pressure (pCO2), dissolved oxygen and chlorophyll. The Guadalquivir river water is rich in TAlk and DIC and its behaviour is mainly conservative along the salinity gradient. Estuarine waters were CO2 oversaturated in all the samplings in space and time. It has been suggested some biogeochemical processes affecting the water pCO2 such as the CO2 flux to the atmosphere, aerobic respiration of organic matter, and carbonate dissolution. The average CO2 flux to the atmosphere is 85.2 mmol m− 2 d− 1 and the total CO2 emission to the atmosphere is 3.2 mol C 106 d− 1. Ventilation of riverine CO2 can contribute to the emission of CO2 from inner estuaries although this factor seems highly variable among European estuaries. It has been estimated that, in the Guadalquivir Estuary, 34% of the total inorganic carbon exported is emitted to the atmosphere.