## 5 Results  
The output files of the model calibration (column #1) and those for the model validation (column #2) as well as the experiment data are available at [[https://darus.uni-stuttgart.de/dataverse/sfb1313_eicp_model_calibration](https://darus.uni-stuttgart.de/dataverse/sfb1313_eicp_model_calibration)]([https://darus.uni-stuttgart.de/dataverse/sfb1313_eicp_model_calibration](https://darus.uni-stuttgart.de/dataverse/sfb1313_eicp_model_calibration)). When using only the ad- and desorption rate coefficients \(k_{\text{a}}\) and \(k_{\text{d}}\) as fitting parameters, the fluctuation of the concentrations can be matched qualitatively (Figures 2 and 3). The estimates for the ad- and desorption coefficients are \(k_{\text{a}}=3.993\times 10^{-2}\) 1/s and \(k_{\text{d}}=8.230\times 10^{-13}\) 1/s. The urea concentrations are predicted qualitatively by the calibrated model. However, some features of the experimental observations are not well reproduced by the calibrated model, such as the depletion of Ca\({}^{2+}\) from the mineralization solution for times of 30 min and later after the end of injection of mineralization solution. Also, the final volume fraction of precipitated calcite along the column, not used for calibration, is overestimated in the first half of the column; see Figure 4. This is somewhat similar to [20], where the model for MICP cannot predict the heterogeneity of the experimental measurements in the inlet region. The overestimation of calcite precipitation close to the inlet suggests that, in the presented model concept (see Section 3), some of the processes might not be correctly parameterized or that some of the boundary, initial, or other experimental conditions were not reproduced in the model. After carefully reexamining the implementation of the experimental setup in the model, we are confident that we represent the experimental conditions in our simulation setup. To find out which processes might not be represented or not be correctly parameterized, we added additional parameters into the set of fitting parameters. While many more processes might be responsible for the mismatch, we chose to limit this study to parameters or processes that have been proven to be useful calibration parameters before to those processes for which we could not find a good parameterization for our conditions in the available literature or based on experimental observations:  
* The apparent ureolytic activity of the crude urease injected (\(c_{\text{u,0}}^{e}\)); see Equation (11). Also for previous MICP model calibrations, it was determined that the ureolytic activity was lower in column experiments than in fully mixed batch experiments (e.g., [21]). * The dissociation constant for ammonia-ammonium (Ka). The current model uses a combination of the relations accounting for high temperature [51] and salinity [52]. We test whether this introduces some error by fitting a multiplier \(f_{\text{pKa}}\) to the calculation of the pKa according to combined relations of [51,52] pKacomb: pKa = \(f_{\text{pKa}}\times\text{pKa}_{\text{comb}}\). * The injected concentrations of calcium and urea \(C_{\text{Ca}^{2+}\text{inj}}\) and \(C_{\text{urea,inj}}\). The measurements suggest that the ratio might not have been equimolar, and less calcium is measured than expected. The initial parameter value guesses and the set upper and lower bounds are given in Table A3 in the Appendix A. When using the injection concentrations as additional fitting parameters, the adsorption rate coefficient is estimated as \(k_{\text{a}}=4.459\times 10^{-2}\) 1/s, an increase of 11.7% compared to the sorption-coefficients-only case. The desorption rate coefficient is estimated to be half an order of magnitude larger than for the base case, \(k_{\text{d}}=3.018\times 10^{-12}\) 1/s.