Modeling salt movement through a Mojave Desert soil

Salt flux through soils can significantly influence local and global processes. For example, desert soils can atypically concentrate NO3- at depth in soil profiles. CaCO3 precipitation/dissolution can play significant roles as either sinks or sources of global carbon. The objectives of this work were to develop a salt-flux model for long-term (>1000 years) simulations of desert soils and examine the consequences of climate, soils, system inputs, and land-use change on salt movement in arid soils.The field study was conducted at the Nevada Test Site in the northern Mojave Desert. New additions to the CALGYP model allowing for site-specific parameterization included stochastic rainfall model, salt inputs, soil water-holding capacities, and soil CO2 profiles. New ions added to the model included Na+, K+, Mg2+, Cl−, and NO3-.About 81% of Ca2+ input remained within the surface 1.0 m of soil as CaCO3, which argues in favor of soil CaCO3 serving as a recalcitrant sink for global carbon. In contrast, ≈99.96% of Na+, K+, Mg2+, Cl−, NO3-, and SO42- ions leached to soil depths >1.0 m and 94.3% leached to soil depths >2.0 m. This is true despite only 1.64% of the rainfall leached beyond 1.0 m and 0.020% of the rainfall leached beyond 2.0 m. The leachability of NO3- and Cl− to soil depths > 2.0 m agrees with NO3- and Cl− accumulations at depth in Mojave Desert soils (1.3–2.7 m). Simulation of extreme events and years with a stochastic rainfall model and accurate soil water-holding capacities are critical for modeling water and salt flux through soils.