The behavior of three hardwood species was investigated in response to natural and artificial light irradiation. The effects of irradiation were evaluated by their color measurement in the CIELab system and Fourier-transform infrared (FTIR) spectra. Both natural light irradiation and artificial light irradiation induced changes in color, such as yellowing and darkening, in the wood species. Comparative in-time evolution of changes in color during artificial light irradiation and natural light irradiation under indoor conditions resulted in an estimated acceleration index that ranged from 60× to 90×.The FTIR spectra highlighted specific changes in surface chemistry during irradiation. Ultraviolet light from natural or artificial sources primarily resulted in lignin degradation.

https://ojs.cnr.ncsu.edu/index.php/BioRes/article/download/BioRes_14_3_6909_You_Photodegradation_Three_Hardwood_Species/7012

Photodegradation of Three Hardwood Species by Sunlight and Xenon Light Sources

The atmospheric conditions of desert environments are important for the protection of Salix psammophila 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 S. psammophila 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 S. psammophila 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 S. psammophila sand barrier. We also found a series of irreversible changes and losses that occurred, which affected the natural material properties of S. psammophila 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 S. psammophila sand barrier. Our results highlighted the importance of the interactions between atmospheric factors and the exposed atmospheric sections of the S. psammophila 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 S. psammophila sand barrier for ecological restoration and desertification reversal, especially in stressful desert environments.

Natural Deterioration Processes of Salix psammophila Sand Barriers in Atmospheric Exposure Section

This paper describes the effects of the absorption of various wave lengths of sun-light and explains the mechanism of photo-induced aging of wood.The effects of light waves on the wood properties such as chemical components,molecular structure,and color and microscopic structural changes are also analyzed.This review provides a useful reference for future research on the anti-aging properties of wood and wood based panels for outdoor applications.

YU Wen-ji

Papers

Review of Research and Development of Photo-Induced Aging of Wood