Bowl effect of irreversible primary salinization driven by geology in Hetao irrigation area, China.

Agricultural irrigation areas around the world employ similar planting methods, but there are notable disparities in salinization mechanism and management strategies. Many scholars have focused on human activities as the main cause of secondary soil salinization, while neglecting the underlying issue of primary soil salinization caused by geological factors. This study takes the Hetao irrigation area in China as a case study, delving into the geological forces responsible for primary salinization. Using historical survey data on geological structure, lake evolution, and sedimentation to analyze the stratigraphic distribution and groundwater storage characteristic. Additionally, using groundwater hydrochemistry data from historical literatures to analyze the concentration, distribution patterns, and source issues of salt ions. The research results show that a novel concept called the "bowl effect" can explain the unique cause of primary salinization in Hetao irrigation area. The bowl effect effectively transforms Hetao irrigation area into an enclosed space, which significantly limits the movement of groundwater and hinders the dilution of highly saline or alkaline water. The bowl effect has broad applicability and can serve as a useful framework for studying primary salinization challenges in agricultural irrigation areas worldwide. This research provides a scientifically reference for selecting salinization control methods, and will benefit local stakeholders, government agencies, and water resource managers.

Wind tunnel experiments for dynamic modeling and analysis of motion trajectories of wind-blown sands.

The hazards associated with travelling on highways in desert regions arise mainly from wind-borne sand disasters, such as complete or partial burial of the road surface by sand particles, and from erosion of the roadbed by the particles. To simulate the damage process caused by sand particles on roads in the desert, scaled-down tests were performed in a wind tunnel whereby sand particles of differing diameters and roadbed models of different gradients were tested and the impact trajectories of the sand particles were captured using a high-speed camera. The results showed that the impact trajectories may be classified into four types, and the proportion of each type is essentially stable with the statistical curves for the trajectories being similar to the Poisson distribution. The diameters of the sand particles and the slopes of the roadbed model influenced the impact trajectories, which also impacted the statistical values for each particle type. Owing to the Magnus force, the direction of rotation and the angular velocity of the sand particles controlled the nature of the collision trajectories; however, the direction of rotation did not remain in a fixed plane and the rotation speed only reached about 20% of the value of the first critical speed. The wind tunnel experiments enable a better understanding of the motion trajectories, rotation speed, force situation, and collision trajectories, providing a useful benchmark for research on wind-induced disasters on roads in desert regions.