Estudio del comportamiento isotópico del sistema CO2(gas) - C02(aq), HC03-, CO32- (25º C), abierto, en condiciones de saturación de C02(gas)

Abstract

The evolution of the isotopic fractionation of the system CO_2(gas) - C0_2(aq), HC0₃^-, CO₃^2- at 25° C and in open system conditions, has been monitored following Δ_{g_DIC} factor between C0_2(g) in solution and total carbon in solution (DIC), as a function of time. Saturation in CO_2(gas) has been reached by addition of HCl to a NaHC0₃ (0.5 M, 600 mL) solution, according to two procedures which allowed the system to interact differently with the open atmosphere. Chemical and isotopic behaviour of the system has been followed to establish the isotopic equilibrium. The pH value does not stabilizes and strong oscillations in the Δ factor are provoked by acidifying the solution and stirring it continuously. One can reach a lesser pH value variation and also lesser oscillations in the Δ factor by a rapid acidifying with no stirring after this process. Isotopic equilibrium within the system is attained after 75 minutes. Values for Δ¹³C_g-DIC varied between -9.0 ± 0.1 and -10.8 ± 0.2 and for Δ¹⁸C_g-DIC between 2.0 ± 0.2 and 3.33 ± 0.17, for the first and second procedures respectively.