Compaction effects on evaporation and salt precipitation in drying porous media

Abstract

Compaction and salinization of soils reduce croplands fertility, affect natural ecosystems, and are major concerns worldwide. Soil compaction compromises soil structure and affects the soil’s hydraulic properties. It therefore may have a significant impact on evaporation and solute transport processes in the soil. In this work, we investigated the combined processes 15 of soil compaction, bare soil evaporation, and salt precipitation. X-ray computed micro tomography techniques were used to study the geometrical soil pore and grain parameters influenced by compaction. The impact of compaction on evaporation and salt precipitation was studied using column experiments. We found that compaction reduced the average grain size and increased the number of grains, due to the crushing of the grains and their 20 translocation within the compacted soil profile. Changes in pore and grain geometry and size were heterogeneously distributed throughout the soil profile, with changes most apparent near the source of compaction, at the soil surface. The column experiments showed that the presence of small pores in the upper layer of the compacted soil profile leads to higher evaporation rates and salt precipitation, due to the compromised hydraulic connectivity to 25 the soil surface and the prolongation of the first stage of evaporation. https://doi.org/10.5194/hess-2021-298 Preprint. Discussion started: 28 June 2021 c © Author(s) 2021. CC BY 4.0 License.