Geochemical Modeling of Carbonate Precipitation Processes Based on Field Data from a Mongolian Alkaline Lake: Implications for Enhanced Rock Weathering Technologies

Abstract

In this study, we developed an evaporation concentration geochemical model for Boon Tsagaan Lake, BTS Lake, in central Mongolia, using measured water quality and discharge data from its sole inflow, the Baidrag River, as initial conditions. Under an open atmosphere Carbon Dioxide system, the model simulates repeated cycles of river inflow and equivalent evaporation, accounting for changes in aqueous species speciation and the formation of metastable carbonate minerals, namely monohydrocalcite, Amorphous Mg carbonate, and Mg silicate hydrate. Results show that the present water chemistry of BTS Lake corresponds to roughly 1,000 years of evaporation concentration, with MHC saturation reached in the fifteenth year of evaporation and subsequent annual precipitation of approximately 3,000 t C as monohydrocalcite. Moreover, this approach demonstrates the quantitative potential to estimate carbonate precipitation rates in diverse alkaline lakes using only lake and river data, and it may be applied to evaluate the efficacy of enhanced rock weathering by adding silicate minerals to inflowing waters.