Biodeterioration of granite monuments by Ochrolechia parella (L.) Mass: AnFT Raman spectroscopic study

Ochrolechia parella is one of the most abundant lichens colonizing granite monuments in the region of Galicia (N.W. Spain). Its interaction with grani te used in the construction of four ancient monuments was studied using FT Raman spectroscopy to evaluate the production of calcium oxalate by this li chen and the relationship of this production with different environmental c onditions, particularly humidity. The results obtained showed that Ochrolec hia parella is an aggressive colonizer, causing chemical disturbances to th e granite through the formation of both calcium oxalate monohydrate and dih ydrate. Apothecial development appears to be related to the production of c alcium oxalate, and humidity determines the state of hydration of the calci um oxalate in the thallus. (C) 1999 John Wiley & Sons, Inc.