The dynamics of the carbonate and the uranyl exchange in aqueous solutions of uranyl(VI) carbonate has been studied in the pH-range 6 < pH < 9 and in the temperature range -5 degrees C < t < +85 degrees C using C-13 and O-17 NMR line broadening, selective magnetization transfer and 2-dimensional exchange spectroscopy (2D-EXSY). This extensive experimental approach was necessary in order to cover the vastly varying time scales for the different exchange processes. Two uranyl complexes dominate the investigated chemical system : the MONOnuclear UO2(CO3)(3)(4-) and the TRINuclear (UO2)(3)(CO3)(6)(6-) complex. In the MONO complex, all the three ligands are bidentately coordinated to uranium. The TRIN complex comprises two different types of carbonate ligands : three TERMinal carbonates with bidentate coordination to the uranium atoms and three CENTral carbonates with a rare mu(3)-coordination to two uranium atoms. In addition, FREE carbonate can be present in the studied solutions as CO32-/HCO3- or CO2(aq), and participate in exchange reactions. The proton exchange for CO32-/ HCO3- is known to be very fast, but it is very slow for HCO3-/CO2(aq). Thus, the exchange between four carbonate sites had to be considered : MONO, CENT and TERM, and FREE.