MECHANISMS OF MICROBIAL BIODETERIORATION OF LIMESTONE IN MAYAN BUILDINGS

摘要

Many of the monuments related to Mayan civilization are suffering deterioration by environmental factors (high temperatures and relative humidities), increasing contamination by natural and anthropogenic sources, and by the action of micro and macroorganisms. Archeological sites and historical monuments in the Mayan area were constructed with different limestones which offer different degradation resistance to the various types of contamination. Two different archeological sites in the Yucatan peninsula, Mexico, were chosen for this study: the urban nucleus of Uxmal, located in a rural environment, and the fortress of Tulum, at the side of the Caribbean sea, exposed to chloride of marine spray and sand erosion. In both sites, heterotrophic bacteria, cyanobacteria and fungi were isolated from the biofilms or crust samples taken in different sampling areas. Anaerobic bacteria were also found in one of the Tulum sampling sites. Crust deposits were observed by using stereoscopic magnifier, SEM and ESEM. Surface analyses were made by means of ED AX and electron microprobe. Two different types of the structural limestone were exposed to natural and accelerated weathering. Possible mechanisms of limestone decay, based on the type of microorganisms found, physicochemical characteristics of the limestones, and environmental factors are discussed.