The formation of pigmented patinas and encrustations on stone monuments, connected to chemical or biological deterioration, can give rise to aesthetic alterations. Pink patinas related to biodeterioration phenomena have been widely observed throughout Europe and in tropical climates, like on the Khmer temple of Bayon (Angkor, Cambodia) or Mayan monuments in Uxmal (Mexico). They generally occur under specific environmental conditions, such as interior or semi-confined areas with specific lighting conditions, a high saline content and substantial variations in humidity and temperature. Other pink discolorations can be observed in the morphology of hard encrustations on the sandstone of one of the buildings of Phnom Krom temple. They occur on exterior surfaces characterised by different conditions than those of the pink alterations at Bayon. Considering their unclear origin and unusual morphology, this paper aims to characterise them and define their chemical or biological origin. The observation of fresh slides, fracture samples and cross-sections with optical and SEM/EDS microscopes shows the presence of very small coccoid cells (0.5 μm) surrounded by an extracellular matrix. SEM-EDS analysis highlighted the presence of Si, Fe, Mg, Ca, Na, K associated with the substrate. Phosphorus, aluminium and a small amount of silicon were detected in correspondence with the body of the patina. The high level of P at the Phnom Krom temple can be traced to salts efflorescence originating in bat guano deposits. It seems necessary to hypothesize the simultaneous presence of other phenomena in order to explain the origin of these encrustations. Microscopic observations have shown a microbiological colonization corresponding to P accumulation, arising, at first, from the guano and then mobilised by wet-dry cycles in areas exposed to direct sunlight. The presence of microorganisms seems able to explain this peculiar coloration, but biomolecular analysis will be needed to understand the precise taxonomy of such bacteria
Tescari, M., Bartoli, F., Casanova Municchia, A., T., B.S., Caneva, G. (2016). Pink patinas and incrustations in tropical environment: Phnom Krom temple case (Angkor, Cambodia). In Science and Art: A Future for Stone (pp. 147-154).
Pink patinas and incrustations in tropical environment: Phnom Krom temple case (Angkor, Cambodia)
TESCARI, MARCO;Bartoli F.;Casanova Municchia A.;Caneva G.
2016-01-01
Abstract
The formation of pigmented patinas and encrustations on stone monuments, connected to chemical or biological deterioration, can give rise to aesthetic alterations. Pink patinas related to biodeterioration phenomena have been widely observed throughout Europe and in tropical climates, like on the Khmer temple of Bayon (Angkor, Cambodia) or Mayan monuments in Uxmal (Mexico). They generally occur under specific environmental conditions, such as interior or semi-confined areas with specific lighting conditions, a high saline content and substantial variations in humidity and temperature. Other pink discolorations can be observed in the morphology of hard encrustations on the sandstone of one of the buildings of Phnom Krom temple. They occur on exterior surfaces characterised by different conditions than those of the pink alterations at Bayon. Considering their unclear origin and unusual morphology, this paper aims to characterise them and define their chemical or biological origin. The observation of fresh slides, fracture samples and cross-sections with optical and SEM/EDS microscopes shows the presence of very small coccoid cells (0.5 μm) surrounded by an extracellular matrix. SEM-EDS analysis highlighted the presence of Si, Fe, Mg, Ca, Na, K associated with the substrate. Phosphorus, aluminium and a small amount of silicon were detected in correspondence with the body of the patina. The high level of P at the Phnom Krom temple can be traced to salts efflorescence originating in bat guano deposits. It seems necessary to hypothesize the simultaneous presence of other phenomena in order to explain the origin of these encrustations. Microscopic observations have shown a microbiological colonization corresponding to P accumulation, arising, at first, from the guano and then mobilised by wet-dry cycles in areas exposed to direct sunlight. The presence of microorganisms seems able to explain this peculiar coloration, but biomolecular analysis will be needed to understand the precise taxonomy of such bacteriaI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
