Rivers play an important role in the carbon cycle, either in CO2 fluxes or as carbon exporters to the oceans. Measures of direct CO2 exchange between terrestrial ecosystems and atmospheres should consider the flows of aquatic systems, so as not to overestimate terrestrial carbon accumulation. The Amazon basin forms the largest and most complex freshwater system in the world, and consequently has an important role in the global carbon cycle. The objective of this work was to evaluate the dynamics of the total dissolved inorganic carbon (CID) in the period between September 2004 and 2004, in its fractions (dissolved CO2 + HCO3- + CO32-) in the waters of the TelesPires and Cristalino rivers, components of the Amazon Basin, in the municipality of AltaFloresta, MT. The concentrations of CID, pH and temperature of the rivers. Based on these determinations and applying the thermodynamic equilibrium equations, the pCO2 and asphrations of the carbonate system were estimated. The rivers showed seasonal variation in pH values, which are closer to neutrality in the dry period. The concentration of HCO3- was significantly higher in the period of drought than in the flood period. Both studied rivers were always supersaturated with CO2 in relation to atmosphere. The concentration of HCO3- was significantly higher in the period of drought than in the flood period. Both studied rivers were always supersaturated with CO2 in relation to atmosphere. The concentration of HCO3- was significantly higher in the period of drought than in the flood period. Both studied rivers were always supersaturated with CO2 in relation to atmosphere.
