Effect of Soil Moisture Content on Condensation Water in Typical Loess and Sandy Soil

Abstract

Many scholars have used samples of drying soil to observe the amount of soil condensation water, which may have exaggerated the amount of regional condensation water, as the soil water content in the natural state was not considered. To analyze the effect of soil moisture content on soil condensation in the natural state, the soil condensation volume in loess and sandy soil under different gravimetric moisture content conditions was measured in the autumn of 2022 and spring of 2023 using micro-lysimeters combined with the weighing method at the groundwater and environment site of Chang’an University, Guanzhong Basin, China. The results showed that the average daily condensation of loess under 0%, 3%, 7%, 11%, and 15% moisture content conditions was 0.34, 0.09, 0.01, −0.05, and −0.07 mm with the condensation days of 54, 40, 24, 21, and 16, respectively, and that of sandy soil was 0.21, −0.02, −0.28, −0.82, and −1.35 mm with condensation days of 54, 24, 2, 3, and 1, respectively. Under the same moisture content conditions, loess had more condensation and condensation days than sandy soil. Soil condensation water occurred mainly when the water content was less than 7%, and it was negatively correlated with soil water content. The quantity of soil condensation water was positively correlated with relative humidity and negatively correlated with air temperature–dew point differences. Relative humidity exceeding 60% and air temperature–dew point differences below 8 °C were more favorable for the formation of soil condensation water. This study provides a reference for the assessment of soil condensation in the natural state.