Although the everlasting preservation of cultural heritage is impossible, it is possible to improve conditions for them to last longer, but first we need to understand the complex relationship between different atmospheric conditions and the decay. Among them, atmospheric deposition plays a crucial role, because is an important cause of decay for built heritage which has been studied for more than half a century, but there have been more discoveries during the last couple of decades, as the relatively low impact of wet deposition (regardless its acidity) compared to dry deposition, the major importance of other atmospheric deposition-related mechanisms as salt recrystallization or the role of biodeterioration. Traditionally, most research on the subject has focused on carbonaceous stone, but nowadays it is known that the damage to building materials is caused by different physicochemical mechanisms into the atmosphere, most involving rainwater. This subject has been scarcely studied for different materials and in places outside Europe, although some researches have been done worldwide so this study is an advance to identify the effect of atmospheric deposition on built heritage in Mexico.

Among its lines of research, the National Autonomous University of Mexico (UNAM) participates with the CDMX Atmospheric Monitoring System (SIMAT) to evaluate the atmospheric deposition, its causes and provenance. The UNAM has also carried surveys on several heritage important sites, as Tulum, Puerto Morelos and El Tajín. Using the data, an Accelerated Weathering Chamber was designed and used to perform test on the mass loss due to the most acidic deposition sampled that the limestone used as building material in the Mayan area will have. Results show that average mass loss is about 241.64 µg/year. A decay function was proposed.

To continue the work and deepen the understanding of built heritage decay on different building materials under different conditions, we have chosen two sites in Mexico City: Templo Mayor, built with volcanic stone and the University City of UNAM built with Portland cement, and one site at Veracruz, San Juan de Ulúa, built with limestone. In this research, currently on development, we have already identified the atmospheric conditions (meteorology, air quality and atmospheric deposition) and will use the data to perform accelerated weathering test to different kinds of decay mechanisms, including salt recrystallization, leaching, dry deposition and thermal fatigue.