The Panamanian UNESCO sites: construction materials and environmental decay

The preliminary results of the environmental impact on the UNESCO sites located in Panama here are presented. This research project was born within a collaboration among the Italian National Research Council, Institute of Atmospheric Sciences and Climate, the University of Ferrara, Department of Earth Sciences, and the Patronages of Panama Viejo and Portobelo-San Lorenzo. A first census of the rocks typologies utilized in the masonries of the monumental site of Panama Viejo and of the fortresses situated in Portobelo and San Lorenzo was performed, in order to understand which are the possible future damages processes, to whom the construction materials of these sites can undergo. In conjunction to this characterization, the evaluation of the current state of conservation was investigated, being a fundamental step for having a clearer hypothesis of the future situations. According to the aforementioned purposes, several samples of natural stone have been collected and analysed from different buildings belonging to the archaeological site and to the fortifications. Specifically, observations of thin sections by Polarized Light Microscopy (PLM), followed by X-Ray Powder Diffraction (XRPD) were carried out for a mineralogical and petrographic characterization and for a primary evaluation of the state of conservation. Moreover, the Environmental Scanning Electron Microscopy (ESEM-EDX) was performed, on both thin sections and bulk samples, to investigate more in detail specific points previously selected by PLM. Furthermore, with the aim to classify the volcanic rocks, the X-Ray Fluorescence (XRF) technique was utilized to obtain the TAS (Total Alkali versus Silica) classification (Le Bas et al, 1986; Le Maitre 1989). Finally, in order to study the physical features, as density and porosity, of the materials, Mercury Intrusion Porosimetry analysis (MIP) was realized. Together with the materials study, for evaluating the potential risks, which can occur to these monuments, related to the tropical climate (Gobierno Nacional-República de Panamá, 2010) the environmental context was investigated, considering several climatic factors and parameters. For this reason, monitoring stations have been selected in proximity of the two areas under study, obtaining 20 years (1975-2005) of data concerning rainfall, temperature and relative humidity (http://biogeodb.stri.si.edu/physical_monitoring/research/panamacanalauthority). Concluding, for the first time the construction materials belonging to the Panamanian cultural heritage, inscribed on the World Heritage List, have been characterized contextually to surrounding environment, basic element for future protection of such important heritage. References Gobierno Nacional -República de Panamá, Autoridad Nacional del Ambiente, Atlas Ambiental, (2010) 26-31 http://biogeodb.stri.si.edu/physical_monitoring/research/panamacanalauthority Le Bas, M.J., Le Maitre , R.W.; Streckeisen, A., Zanettin, B.; A Chemical Classification of Volcanic Rocks based on the Total-Alkali-Silica Diagram; Journ. of Petrol., Vol.: 27, (1986) 745-750 Le Maitre, R.W., A Classification of Igneous Rocks and Glossary of Terms; Recommendations of the IUGS, Subcommission on the Systematics of Igneous Rocks, (1989) 33-38