Mechanistic Modeling of Soil Inorganic Carbon Dynamics in Controlled Experiments

We introduce here the development and testing of a mechanistic model accounting for inorganic carbon dynamics in soil. We designed a microbially induced carbonate precipitation version 1 (MICPv1) reaction network to describe the transport, precipitation, and dissolution of calcium carbonate under the effect of dynamic H + and HCO 3 − concentrations driven by microbial consumption of yeast extract and acetate as the source of C for growth and urea as a source of nitrogen and bicarbonate. MICPv1, embedded in the BRTSim general‐purpose solver (BRTSim‐MICPv1), was solved explicitly in space and time to replicate prior experiments in a 3.7‐m soil column with three soil types, subject to two different nutrient treatments, and lasting from 17 to 26 days. We found that BRTSim‐MICPv1 could capture the main experimental features in urea, NH 4 + , microbial biomass dynamics, and calcite precipitation both spatially and over time (Nash‐Sutcliffe NSE > 0.51; NRMSD < 27%). A Monte Carlo stochastic analysis on BRTSim‐MICPv1 parameterization showed that the carbonate dynamics response to parameter variability was robust and more accentuated in the column with high nutrient input. Finally, we show that BRTSim‐MICPv1 was mass conservative and able to correctly solve for chemical equilibrium and could be used to track the sources and sinks of Ca 2+ and HCO 3 − to support our findings.