Benchmarking the reactive transport code SCEPTER v1.0.2

Abstract. One-dimensional reactive transport codes are powerful tools for examining a range of geologic, biogeochemical, and agronomic phenomena. The reactive transport code SCEPTER (Soil Cycles of Elements simulator for Predicting TERrestrial regulation of greenhouse gases) has been recently developed for simulating a range of processes controlling soil biogeochemistry in managed lands, with a particular emphasis on soil pH management and enhanced weathering as a carbon sequestration strategy. While much of the basic framework implemented in SCEPTER is structurally and parametrically akin to existing reactive transport codes, its behavior has not been systematically benchmarked against other longstanding reactive transport models. Here, we quantitatively evaluate the performance of SCEPTER relative to a range of other reactive-transport models through a series of benchmarking experiments designed to assess the capacity of the code to simulate: (1) soil hydrology and fluid transport; (2) charge balance during cation exchange; and (3) mineral dissolution/precipitation, with (2) and (3) accompanied by diffusive/advective fluid transport and equilibria for aqueous speciation and gas dissolution into pore fluids. We show that the performance of SCEPTER is functionally identical to all other hydrological and reactive transport codes across the simulated benchmark conditions and discuss the emerging need for a reactive transport model benchmarking procedure that is fit for the purpose of predictive modeling of soil pH management in agricultural lands.