This study investigates salt weathering in the indoor, humid environment of China's Jinsha earthen site. Methods such as digital microscope, scanning electron microscopy (SEM), ion chromatography (IC), energy dispersive spectroscopy (EDS), and laser particle size analysis were employed to collect and analyze samples from four heavily weathered walls. The sampling approach took into account differences in depth and height and prioritized the extraction from various weathering layers to unveil the attributes, causes, and mechanisms of salt weathering. The findings indicate that the Jinsha site's eastern segment suffered salt-induced damage, such as powdering, salt crusts, and blistering, due to the presence of gypsum and magnesium sulfate. These salts were primarily sourced from groundwater. Groundwater ions ascended to the site's surface via capillary action, instigating various forms of salt damage. Salt damage severity has a direct link to salt and moisture content. The degradation patterns can be categorized into powder and multi-layered composite deterioration, both seems related to soil particle composition. Powder deterioration tends to occur when the sand content exceeds 40%. This research proposes preservation strategies that focus on managing groundwater and conducting environmental surveillance. These measures are designed to effectively address and mitigate the risks associated with salt damage.

Usually, the term 'rising damp' refers to capillary water rising from the ground which may damage architectural heritage. In this work, the essence of rising damp in extremely arid regions and its driving force are revealed based on experiments monitoring the relative humidity (RH) and atmospheric pressure (AP) in the Dunhuang Mogao Grottoes. The air in the vadose zone, the unsaturated region between ground level and the top of the water table, is here referred to as 'earth-air'. When the AP rises, the earth-air is compressed, and atmospheric air enters into the soil. Then, when the AP drops, moist earth-air expands and rises into the structure. The RH in the soil is thus negatively correlated with the AP, yielding a correlation coefficient of up to -0.94. Under the action of this long-term dry-wet alternation, the salt present in the building near ground undergoes repeated cycles of crystallization and dissolution, resulting in efflorescence and a deterioration zone. Therefore, the deterioration due to rising damp in extremely arid regions is caused by the rising of moist earth-air rather than capillarity. The height to which it rises is directly proportional to the amplitude of the daily AP fluctuation and thickness of the vadose zone, exhibiting a bimodal fluctuation pattern on a daily scale. The discovery of this mechanism of rising damp provides a scientific basis for preventive conservation interventions.