Mechanism of salt-induced deterioration of stone stele in arid environments of Northwest China

The Imperial Stele of Gan’en Monastery, a significant Ming Dynasty sandstone relic and a testament to Han-Tibetan cultural exchange, is severely threatened by salt-induced deterioration. To investigate the mechanisms of salt weathering affecting stone relics in arid northwestern environments, this study employs a comprehensive analytical approach including microscopic, mineralogical, and chemical analyses. The results reveal that the primary soluble salts responsible for deterioration are sodium sulfate and sodium carbonate, mainly originating from capillary rise of saline groundwater and, to a lesser extent, from weathering of inherent minerals. The pore structure of the sandstone, characterized by fine intergranular pores with limited connectivity, facilitates salt accumulation and crystallization. Crystallization and hydration pressures from repeated dissolution-recrystallization cycles, driven by pronounced diurnal and seasonal temperature and humidity fluctuations, induce progressive structural weakening, manifesting as powdering, flaking, and loss of surface inscriptions. These findings provide a scientific basis for developing targeted conservation strategies for this valuable cultural heritage.