Equilibration Times of Dissolved Inorganic Carbon During pH Transitions

Equilibration times of dissolved inorganic carbon (DIC) depend on conversion reactions between CO2(aq) and the dissociation products of carbonic acid [S = (H2CO3) + (HCO3−) + (CO32−)]. Here, we develop analytical equations and a numerical model to calculate chemical equilibration times of DIC during...

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Bibliographic Details
Published in:Frontiers in Earth Science
Main Authors: Ziv Sade, Shahar Hegyi, Itay Halevy
Format: Article in Journal/Newspaper
Language:English
Published: Frontiers Media S.A. 2022
Subjects:
dissolved inorganic carbon
salinity effects
buffered solutions
unbuffered solutions
chemical equilibrium
Science
Q
Carbonic acid
Online Access:https://doi.org/10.3389/feart.2021.792858
https://doaj.org/article/77a4bb7e5e5148fe96b1c3e8d08b5466
Description
Summary:Equilibration times of dissolved inorganic carbon (DIC) depend on conversion reactions between CO2(aq) and the dissociation products of carbonic acid [S = (H2CO3) + (HCO3−) + (CO32−)]. Here, we develop analytical equations and a numerical model to calculate chemical equilibration times of DIC during pH transitions in buffered and unbuffered solutions. We approximate the equilibration degree of the DIC reservoir by the smaller of the CO2(aq) and S pools at the new pH, since the smaller pool is always farther from equilibrium during the chemical evolution. Both the amount of DIC converted and the rate of conversion differ between a pH increase and decrease, leading to distinct equilibration times for these general cases. Alkalinity perturbations in unbuffered solutions initially drive pH overshoots (increase or decrease) relative to the new equilibrium pH. The increased rates of DIC conversion associated with the pH overshoot yield shorter equilibration times compared to buffered solutions. Salinity has opposing effects on buffered and unbuffered solutions, decreasing and increasing equilibration times, respectively.

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