Study on the Gas–Rock Interfacial Deterioration Mechanisms of Limestone Cultural Heritage: A Case Study of the Qingyunshan Cliff Sculptures, China

ABSTRACT Limestone cultural heritage exposed to the atmosphere over long periods undergoes deterioration processes not solely governed by water–rock interactions such as precipitation and seepage. Under relatively dry or semienclosed conditions, gas–rock interfacial reactions may dominate structural degradation. This study takes the Qingyunshan Cliff Sculptures as the research object. Under conditions without direct involvement of liquid water, laboratory‐based accelerated simulations were conducted to investigate the gas–rock interfacial reactions and microstructural evolution of limestone under SO 2 , NO x , and CO 2 environments. A comprehensive analytical framework was employed, including macroscopic observation, mass change monitoring, polarized light microscopy (PLM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), ion migration testing, and BET pore structure analysis, to reveal distinct reaction pathways and deterioration mechanisms. Results show that the final average mass loss rates under SO 2 , NO x , and CO 2 environments were 4.32%, 20.72%, and 0.77%, respectively. Under SO 2 environments, gypsum formation induced crystallization pressure, leading to a coupled “dissolution–sulfate crystallization” mechanism. In the NO x environment, highly soluble nitrates significantly enhanced calcium migration, resulting in severe structural disintegration within 49 days. In contrast, CO 2 ‐induced deterioration was dominated by gradual carbonation dissolution, with limited secondary salt accumulation but potential long‐term exfoliation. Pore structure analysis indicates a general reduction in micropore content, enlargement of pore size, and reconstruction of pore networks. Connectivity enhancement was most pronounced under NO x conditions, whereas SO 2 exposure caused partial micropore filling and reduced porosity. This study demonstrates that atmospheric gasses can dominate limestone deterioration through gas–rock interactions even without continuous liquid water, complementing traditional water–rock frameworks and providing a basis for risk assessment and conservation strategies in dry and semienclosed environments.