The effect of temperature and wetting–drying cycles on soil wettability: Dynamic molecular restructuring processes at the solid–water–air interface

The impact of heat treatment and wetting–drying cycles on the wetting properties sandy forest soils was explored. Topsoil upper subsoil were sampled at three beech sites in northern Germany. air-dried treated 20, 40 80°C for 24 h, with materials 20°C serving as reference. After wetting, or shock-frozen liquid N2 freeze-dried. Interfacial monitored by sessile drop contact angles (CAs) X-ray photoelectron spectroscopy (XPS), which provide physical chemical information outermost particle interface layer. CAs reference samples around 90° significantly increased after 80°C-treatment to >90°, whereas 40°C-treatment had comparison no distinct CA. Depending initial temperature treatment, air-drying decreased CA 60–80% shock-freezing freeze-drying 10–50% value. Results suggest that may preserve organic matter molecular structure prevails during water solid–liquid interface, thus indicating wettability wet surface. Generally, least 80°C-treated material. XPS analysis confirmed dynamic interfacial restructuring processes changes O C content non-polar compounds. A second two again proved pronounced CA, especially prior freeze-drying. In conclusion, findings our study indicate a sensitive partly reversible reorganization solid properties. conceptually be used develop models, are needed simulate interplay between soil hydraulic functions exposed intensive periodic moisture fluctuations. Highlights T > 40°C angle; angle depended how removed Shock-freezing preserves wetted state Contact confirm due change goes along element within depth