Natural Deterioration Processes of Sand Barriers in Atmospheric Exposure Section.

The atmospheric conditions of desert environments are important for the protection of Sand Barrier, and these conditions can affect and change the structure and performance of the sand barrier, causing them to lose their wind proofing and sand fixing benefits. In this study, we have first examined the key environmental factors that affect the exposure of sand barrier. Then, we assessed how key factors in the desert atmospheric environment affect structural aging and performance. The relative crystallinity and chemical composition changes in the sand barrier were measured by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), and the main degradation factors and processes were discussed. The results showed that the degradation degree of the exposed sand barrier was mainly affected by moisture and ultraviolet radiation. Lignin was the main component and the source of photodegradation and photodiscoloration observed in the sand barrier. However, other polysaccharides, such as cellulose and hemicellulose, were less affected by photodegradation. The stress generated by alternating desorption-absorption was the main cause of the expansion and contraction, deformation, cracking, and warping observed in sand barrier. We also found a series of irreversible changes and losses that occurred, which affected the natural material properties of sand barrier exposed to atmospheric conditions for several years. Exposure times between 5 and 7 years were the most important turning point in time for determining the deterioration of the sand barrier. Our results highlighted the importance of the interactions between atmospheric factors and the exposed atmospheric sections of the sand barrier from the perspective of environmental effects. However, the exact mechanisms of the sand barrier deterioration still need further investigation. Nevertheless, our overall findings advanced the current understanding of the environmental effects of sand barrier for ecological restoration and desertification reversal, especially in stressful desert environments.