Dataset: Experimental data and model code for d18O and d47 equilibration kinetics

We analyzed oxygen and clumped isotope values of inorganic BaCO3 samples from Uchikawa and Zeebe (2012), which were quantitatively precipitated from NaHCO3 solutions over the course of isotopic equilibration. These time-series quantitative inorganic BaCO3 precipitation experiments were conducted under a normal condition at 25 °C and in the presence of varying amount of carbonic anhydrase enzyme that is known to catalyze CO2 hydration and known to be possessed by a range of marine calcareous organisms.

Summary of new δ18O and Δ47 values measured on BaCO3 samples from Uchikawa and Zeebe (2012). These BaCO3 samples were quantitatively precipitated from NaHCO3 solutions at various times over the course of isotopic equilibration at 25 °C. Also included in the file are δ18O and Δ47 values of the NaHCO3 used in the experiments and original δ18O data by Uchikawa and Zeebe (2012) on the BaCO3 samples and experimental NaHCO3 and H2O.

We also developed a fully open-sourced numerical codes (ExClump38 model) that can simulate the time-course of oxygen and clumped isotope equilibration in the dissolved carbonate system as a function of temperature, pH and carbonic anhydrase concentration by extending the work of Chen et al. (2018). By extending the framework of earlier work (Chen et al., 2018), this model tracks temporal change in the abundance of singly (i.e., δ13C and δ18O) and doubly-substituted (i.e., Δ47) aqueous CO2 and the sum of HCO3- and CO32- (referred to as the dissolved carbonate pool: DCP) from a given initial condition/state to the expected isotopic equilibrium in the dissolved carbonate system.

Matlab codes for the ExClump38 model and accompanying experimental data. These data are attached to this datapackage as a supplemental file. The zipfile contains 9 different files. Descriptions of the files:

* ExClump38.m: A Matlab m-file for the ExClump38 model, which can simulate the progress of isotopic (δ18O and Δ47) equilibration in the dissolved carbonate system as a function of temperature, pH and carbonic anhydrase activity.

* IsoEquilibration.m: A Matlab m-file containing a set of differential equations to be solved in the ExClump38 model. This file needs to be downloaded with ExClump.m and stored in the same folder.

* Model_Constants.m: A Matlab m-file containing a set of equilibrium and kinetic rate constants as well as isotope fractionation factors used in the ExClump38 model. This file needs to be downloaded with ExClump.m and stored in the same folder.

* Data_Entry.m: A supplementary Matlab m-file for the entry of our experimental data as well as the initial condition for each experimental series for the ExClump38 model.

* TS2.dat: A supplementary .dat file needed for the entry of isotope data from the “TS-2” experimental series. The TS-2 experiments were conducted at T = 25 °C, pHNBS = 8.9 and in the absence of carbonic anhydrase enzyme.

* TS2_CAmn.dat: A supplementary .dat file needed for the entry of isotope data from the “TS-mnCA” experimental series. The TS-2 experiments were conducted at T = 25 °C and pHNBS = 8.9, with the addition of carbonic anhydrase enzyme to a concentration of 3.7 nM.

* TS2_CA2.dat: A supplementary .dat file needed for the entry of isotope data from the “TS-2CA” experimental series. The TS-2 experiments were conducted T = 25 °C and pHNBS = 8.9, with the addition of carbonic anhydrase enzyme to a concentration of 9.3 nM.

* TS2_CA3.dat: A supplementary .dat file needed for the entry of isotope data from the “TS-3CA” experimental series. The TS-2 experiments were conducted T = 25 °C and pHNBS = 8.9, with the addition of carbonic anhydrase enzyme to a concentration of 19 nM.

* SS18.dat: A supplementary .dat file needed for the entry of isotope data from similar experiments done by Staudigel and Swart (2018) at T = 25 °C.

All of the .dat files are organized as follows:

* 1st column (far left): pHNBS of the experimental NaHCO3 solution.
* 2nd column: Elapsed equilibration time (minutes)
* 3rd column: δ13C of BaCO3 samples (‰, VPDB)
* 4th column: δ13C measurement uncertainty for BaCO3 (1σ standard error, ‰ VPDB)
* 5th column: δ18O of BaCO3 samples (‰, VPDB)
* 6th column: δ18O measurement uncertainty for BaCO3 (1σ standard error, ‰ VSMOW)
* 7th column: δ18O of experimental H2O (‰, VSMOW) from Uchikawa & Zeebe (2012)
* 8th column: δ18O measurement uncertainty for H2O (1σ standard error, ‰ VSMOW)
* 9th column: Δ47 of BaCO3 samples (‰, ARF)
* 10th column (far right): Δ47 measurement uncertainty (1σ standard error, ‰ ARF)

Related publications:

* Data contained original data for d18O of H2O from  Uchikawa, J., & Zeebe, R. E. (2012)
* The numerical model is adopted and modified from Chen et al. (2018)
* The model is also applied to (their dataset is attached as SS18): Staudige & Swart (2018)