Characteristics of carbonate building stones that influence the dry deposition of acidic gases

The behaviour of several porous carbonate building stones used in Spanish and English monuments was compared. Stones were exposed to urban and suburban environments and subjected to simulated SO 2 atmospheres in the laboratory. Physical properties that affect the transfer of moisture were determined before and after exposure, and related to the degree of reaction of the stones. The degree of reaction was determined by analysing the reaction products. Results showed that physical properties influenced the reactivity of the stones. These characteristics also changed as the stones weathered due to the different concentrations of impurities in the material. Moreover, stones with a high specific surface area and/or a deliquescent salt content may promote more NO x dry deposition.