The importance of atmospheric effects on biodeterioration of cultural heritage constructional materials

The three important factors influencing the deterioration of monuments and buildings belonging to the cultural heritage are: (a) biodeterioration processes, (b) atmospheric deterioration or weathering of the materials exposed to open air, and (c) natural and anthropogenic pollution. Thus, the environment plays a decisive role in the type and extent of deterioration processes experienced by the cultural property. In the literature on atmospheric corrosion or weathering of structural materials of cultural heritage there is a lack of understanding of the relevance of biodeterioration processes. Moreover, the close relationship between the environment and the microbial communities colonizing monuments and buildings is generally ignored. With the aim of clarifying this relationship a brief overview of several cases of biodeterioration in four sites of Latin American cultural heritage is presented here. An analysis of the structural material composition and its physicochemical characteristics was made in each case by using surface analysis techniques complemented by electron microscopy. Microbiological techniques for the isolation and culture of microbial contaminants were also used, and the information was correlated with experimental data on the concentration of atmospheric pollutants in each particular case. A synergistic relationship between biological and atmospheric effects on the deterioration of structural materials was observed, although in marine and in industrial/urban atmospheres the weathering effects were predominant.