The effect of air pollution on stone decay: the decay of the Drachenfels trachyte in industrial, urban, and rural environments—a case study of the Cologne, Altenberg and Xanten cathedrals

摘要: Severe stone deterioration is evident at the Cologne cathedral. In particular, “Drachenfels” trachyte, which was building material of medieval construction period, shows significant structural as well massive formation gypsum crusts. The present article investigates crust on limestone, sandstone, and volcanic rock from cathedral Xanten Altenberg cathedrals. These three buildings, showing varying degrees deterioration, are located in different areas exposed to industrial, urban, rural pollution. Thin laminar black framboidal crusts form calcareous silicate stone. lack a intrinsic calcium sulfur source for Drachenfels trachyte indicates major extrinsic environmental impact: sufficient offer SOx pollutant fluxes external sources (e.g., pollution, mortars, neighboring calcite stones). Chemical analyses reveal strong enrichment within higher concentrations lead other pollutants (arsenic, antimony, bismuth, tin, etc.), generally can be linked traffic industry. weathering an industrial environment clearly distinguishable that areas. Scanning electron microscopy observations confirm total amount pollution less than XRF show occurs lower amounts Altenberg. This correlates with measured SO2 content intensity decay locations. Furthermore, types crusts, e.g., laminar, differentiated assigned contribute degradation historic material. They enhance mechanical moisture-related processes by chemical corrosion rock-forming minerals. Although air have shown decrease over past 30 years, connection still observed. not only contemporary or recent emissions, but also considered.