A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Oxalate Patinas on Stone Monuments in the Venetian Lagoon: Characterization and Origin
Calcium oxalate patinas have been sampled on architectural elements of two ancient churches located on Torcello Island (Venetian Lagoon) and subsequently analyzed. The site had been selected presenting patinas of exceptional amount and thickness, elsewhere generally found as thin alteration layers covering stone surfaces or within black crusts on monuments in urban environments. Optical and mineralogical analyses suggest that these patinas are not the result of a simple deposition process, but originate as surface “transformations” of the substrate, and are mainly composed of dihydrate calcium oxalate (weddellite) and gypsum. Among the experimental techniques, isotope analyses (C and S) have been specifically carried out aiming at achieving a better understanding of their origin and possible causes of formation. The observed carbon isotopic fingerprint reveals in fact a strong biological fractionation recorded in the oxalate patina (δ13C ranging from −22.3‰ to −28.0‰), almost exclusively attributable to C3 pathway photosynthesis processes. Slightly negative sulfur isotope ratio values seem to be inversely correlated with patina exposure to atmospheric agents and pollutants. The results obtained prove that calcium oxalate originates from a biomineralization process induced by lichen colonization in specific environmental conditions.
Oxalate Patinas on Stone Monuments in the Venetian Lagoon: Characterization and Origin
Calcium oxalate patinas have been sampled on architectural elements of two ancient churches located on Torcello Island (Venetian Lagoon) and subsequently analyzed. The site had been selected presenting patinas of exceptional amount and thickness, elsewhere generally found as thin alteration layers covering stone surfaces or within black crusts on monuments in urban environments. Optical and mineralogical analyses suggest that these patinas are not the result of a simple deposition process, but originate as surface “transformations” of the substrate, and are mainly composed of dihydrate calcium oxalate (weddellite) and gypsum. Among the experimental techniques, isotope analyses (C and S) have been specifically carried out aiming at achieving a better understanding of their origin and possible causes of formation. The observed carbon isotopic fingerprint reveals in fact a strong biological fractionation recorded in the oxalate patina (δ13C ranging from −22.3‰ to −28.0‰), almost exclusively attributable to C3 pathway photosynthesis processes. Slightly negative sulfur isotope ratio values seem to be inversely correlated with patina exposure to atmospheric agents and pollutants. The results obtained prove that calcium oxalate originates from a biomineralization process induced by lichen colonization in specific environmental conditions.
Oxalate Patinas on Stone Monuments in the Venetian Lagoon: Characterization and Origin
Bonazza, Alessandra (author) / Natali, Claudio (author) / Ghedini, Nadia (author) / Vaccaro, Carmela (author) / Sabbioni, Cristina (author)
International Journal of Architectural Heritage ; 9 ; 542-552
2015-07-04
11 pages
Article (Journal)
Electronic Resource
English
Presence of D, L amino acids in oxalate patinas on a stone monument
| British Library Conference Proceedings | 2000
Evaluation of Deterioration Processes on the Istria Stone of Venetian Monuments
| British Library Conference Proceedings | 1992
Are patinas of mediterranean monuments really related to the rock substrate?
| British Library Conference Proceedings | 1996
Venetian vernacular architecture : traditional housing in the Venetian lagoon
| UB Braunschweig | 1989