关键词: 凝结水, 矿物复合保水剂, 人工保水层, 蒸发, 微渗计, 西北干旱地区

Abstract:

This study was undertaken at the comprehensive field test site of the soil improvement experimental station of the Shihezi 121 Regiment in the northern Xinjiang Uygur Autonomous Region, China; this site is in the middle of the northern foot of the Tianshan Mountains, along the south margin of the vast Gurbantunggut Desert. In the study, a weighing method is used to conduct an experiment on the efficiency of a mineral superabsorbent composite in the utilization of water from condensation in arid areas. On the basis of the obtained experimental data, analysis was conducted on the generation law of condensation water in the region, the condensation water retention effect of the artificial water retention layer formed after introducing the mineral superabsorbent composite to the topsoil, and the transport law of the zero-flux plane underground with temperature and time. In the experiment, a microlysimeter was used to verify the existence and quantity of condensation water in the region of interest. Through continuous observation, the generation time of the condensation water in the region was investigated. Using bottom-sealed and bottom-open test tubes of the microlysimeter, the condensation water was determined to come from two sources: the condensation of water vapor in the air onto the surface soil as the surface temperature dropped and the condensation of water vapor from the zero-flux plane at a certain depth under the surface soil. The experimental data indicate that the condensation water in the region forms primarily during the 22:00-09:00 time period. The condensation process begins at approximately 21:00, and the yield of condensation water is initially high, later reducing slightly at around 06:00. As the difference between the ground temperature and near-surface temperature narrows after sunrise, the condensation gradually decreases and transitions into evaporation. The main factors influencing the formation of condensation water are the near-surface air temperature, the near-surface soil temperature, the relative humidity in the air, and the wind speed. The introduction of a mineral superabsorbent composite to the near-surface soil was found to cause the mixed layer to become an artificial water retention layer, which affects the quantity of both condensation and evaporation in the region. The experimental results reveal that condensation water forms mainly at the soil surface; the volume of condensation water varies in the range of 0-10 cm, and the artificial water retention layer demonstrated the best retention effect on condensation water at a distance 5-10 cm from the surface. In arid areas, although the volume of condensation is much smaller than that of evaporation, the huge temperature difference between day and night is favorable to the formation of condensation water. The range of the change in the ground temperature mainly occurs within 0-45 cm underground and occurs faster than the change in the near-surface air temperature, thus favoring the formation of condensation water. Condensation water is extremely valuable to drought-enduring plants in arid areas. Studies on the water retention effect of the artificial layer formed by adding a mineral superabsorbent composite on condensation water in arid areas are very important for the protection of vegetation, the identification of potential ecoenvironmental improvements, and the control of desertification in arid and semiarid regions.

Key words: condensed water, mineral composite water-retaining agent, artificial water-retaining layer, evaporation, micro-osmometer, arid region in northwest China