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Lichen biodeterioration of ecclesiastical monuments in northern Spain
Susana E Jorge Villar1, Howell G M Edwards, Mark R D Seaward
1Department of Chemical and Forensic Sciences, University of Bradford, Bradford BD7 1DP, UK. seju@ubu.es
Summary
FT-Raman spectroscopy non-destructively analyzed lichen pigments and minerals on building stones. This technique shows potential for identifying lichen species without damaging samples, aiding in their study on historical structures.
Area of Science:
- Bioanalytical Chemistry
- Spectroscopy
- Lichenology
- Heritage Science
Background:
- Lichens on historical buildings present identification challenges.
- Non-destructive analysis methods are crucial for heritage materials.
- FT-Raman spectroscopy offers potential for in-situ chemical analysis.
Purpose of the Study:
- To analyze pigments and mineral inclusions in lichens on ecclesiastical buildings.
- To assess the applicability of FT-Raman spectroscopy for non-destructive lichen identification.
- To investigate the source of calcium oxalate in lichens on various substrata.
Main Methods:
- Non-destructive FT-Raman spectroscopy of seven lichen species on limestone and sandstone.
- Analysis of vibrational band assignments correlated with wet chemical extraction data.
- Identification of beta-carotene and calcium oxalates (whewellite, weddelite).
Main Results:
- Beta-carotene identified as the major pigment in all analyzed lichen species.
- Calcium oxalate monohydrate (whewellite) and dihydrate (weddelite) detected, even on non-calcareous substrates.
- Raman spectral biomarkers largely agreed with chemical extraction profiles.
Conclusions:
- FT-Raman spectroscopy is a viable non-destructive method for analyzing lichen pigments and minerals.
- The study demonstrates potential for taxonomic identification of lichens using Raman spectroscopy.
- Calcium sources for oxalate formation on non-calcareous substrates likely originate from atmospheric deposition.