Organic and inorganic compounds in limestone weathering crusts from cathedrals in Southern and Western Europe

Limestone and weathering crusts have been studied at the major cathedrals of Sevilla, in southwestern Spain, and Mechelen, in northern Belgium. These cities have very different climatic and environmental conditions. The deterioration characteristics of the limestone in both localities have been compared. Detailed petrographical characterization was carried out for the different building stones, including restoration materials. The bulk and trace inorganic composition of the stones and crusts was assessed, and the leachable ions were analyzed, while elemental concentration profiles with depth were studied with electron microprobe analysis. The organic compounds in the black weathering crusts have also been studied and compared. In the different types of limestone, the deterioration is largely influenced by the petrographie characteristics of the stone. Gypsum crusts from Mechelen and Sevilla show variable textures, even on the same stone types. Sulfatation of calcite provides Ca for the gypsum crusts. Except fora part of the Sr and Fe fractions in the crust, all other elements may be of external origin. Concentrations of the various elements are more or less comparable in crusts from Mechelen and Sevilla. External inorganic particles consist of fly ash, quartz, clay, and glauconite. Most of the organic material appeared to be of anthropogenic origin, due to combustion processes, while a minor fraction originated from cuticular waxes of higher plants.This work was supported by the Commission of the European Community, Project STEP-CT90-0107.Peer Reviewe