Applications of analytical pyrolysis to the study of stony cultural properties

Abstract

Pyrolysis-gas chromatography/mass spectrometry was used to study the organic compounds present in weathered building materials from historic buildings and monuments. Three very different materials were investigated: a black layer from a terracotta statue from the Pardon Gate, Cathedral of Seville, Spain; a green layer found beneath a black sulphated crust from the Cathedral of Seville; and a black coating covering the stones of the Old Church of Delft, The Netherlands. From a general pattern in which n-alkanes and polycyclic aromatic hydrocarbons were the main components of black sulphated crust (as exemplified by the layer covering the terracotta statue), biogenic inputs could be easily recognized by study of specific markers (as denoted the contribution of the cyanobacterium Phormidium sp. to the green layer). Also an odd input, as in the case of the tar constituting the black coating of the stones of the Dutch church, was readily segregated. The results obtained indicate that analyticalpyrolysis may be used as a first approach for analysis of organic matter within mineral matrices in cultural properties.