Differences in Water Vapor Adsorption-Desorption of Non Aged and 3-Year Aged Biochar in Sandy Spodosols

Ageing of biochars in soil affects their surface properties and can cause changes in water vapor adsorption-desorption processes. Measurements of hygroscopic water contents and corresponding water potentials of non aged and 3-year aged biochars as well as of sandy soils with medium and high quality were carried out during 5 cycles of water vapor adsorption-desorption processes at a room temperature of 23.5 °C. The results showed a significantly lower content of maximum hygroscopic water in the aged biochars than that in the non aged biochar at the end of water vapor adsorption processes at high air humidity. A significantly higher affinity of the high quality soil to water vapor resulted in insignificant differences in the maximum hygroscopic water content and in significant changes in the corresponding water potentials as compared to the same properties of the soil with medium quality. Minimum content of hygroscopic water was significantly lower in the non aged biochar than in the aged biochars at the end of the water desorption processes at ambient laboratory atmosphere. There were insignificant differences in minimum contents of hygroscopic water and in the corresponding water potentials of the aged biochars from soils with medium and high quality.