Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation
Abstract Much stone sculptural and architectural heritage is crumbling, especially in intense tropical environments. This is exemplified by significant losses on carvings made of tuff stone at the Classic Maya site of Copan. Here we demonstrate that Copan stone primarily decays due to stress generat...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Nature Portfolio
2021-08-01
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| Series: | npj Materials Degradation |
| Online Access: | https://doi.org/10.1038/s41529-021-00191-4 |
| _version_ | 1818843944841117696 |
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| author | Kerstin Elert Encarnación Ruiz-Agudo Fadwa Jroundi Maria Teresa Gonzalez-Muñoz Barbara W. Fash William L. Fash Nieves Valentin Alberto de Tagle Carlos Rodriguez-Navarro |
| author_facet | Kerstin Elert Encarnación Ruiz-Agudo Fadwa Jroundi Maria Teresa Gonzalez-Muñoz Barbara W. Fash William L. Fash Nieves Valentin Alberto de Tagle Carlos Rodriguez-Navarro |
| author_sort | Kerstin Elert |
| collection | DOAJ |
| description | Abstract Much stone sculptural and architectural heritage is crumbling, especially in intense tropical environments. This is exemplified by significant losses on carvings made of tuff stone at the Classic Maya site of Copan. Here we demonstrate that Copan stone primarily decays due to stress generated by humidity-related clay swelling resulting in spalling and material loss, a damaging process that appears to be facilitated by the microbial bioweathering of the tuff stone minerals (particularly feldspars). Such a weathering process is not prevented by traditional polymer- and alkoxysilane-based consolidants applied in the past. As an alternative to such unsuccessful conservation treatments, we prove the effectiveness of a bioconservation treatment based on the application of a sterile nutritional solution that selectively activates the stone´s indigenous bacteria able to produce CaCO3 biocement. The treatment generates a bond with the original matrix to significantly strengthen areas of loss, while unexpectedly, bacterial exopolymeric substances (EPS) impart hydrophobicity and reduce clay swelling. This environmentally-friendly bioconservation treatment is able to effectively and safely preserve fragile stones in tropical conditions, opening the possibility for its widespread application in the Maya area, and elsewhere. |
| first_indexed | 2024-12-19T05:05:55Z |
| format | Article |
| id | doaj.art-74184a82527b4348a812d08a40b94d83 |
| institution | Directory Open Access Journal |
| issn | 2397-2106 |
| language | English |
| last_indexed | 2024-12-19T05:05:55Z |
| publishDate | 2021-08-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | npj Materials Degradation |
| spelling | doaj.art-74184a82527b4348a812d08a40b94d832022-12-21T20:34:57ZengNature Portfolionpj Materials Degradation2397-21062021-08-015111210.1038/s41529-021-00191-4Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservationKerstin Elert0Encarnación Ruiz-Agudo1Fadwa Jroundi2Maria Teresa Gonzalez-Muñoz3Barbara W. Fash4William L. Fash5Nieves Valentin6Alberto de Tagle7Carlos Rodriguez-Navarro8Department of Mineralogy and Petrology, University of GranadaDepartment of Mineralogy and Petrology, University of GranadaDepartment of Microbiology, University of GranadaDepartment of Microbiology, University of GranadaPeabody Museum, Harvard UniversityDepartment of Anthropology, Harvard UniversityConservation consultantConservation consultantDepartment of Mineralogy and Petrology, University of GranadaAbstract Much stone sculptural and architectural heritage is crumbling, especially in intense tropical environments. This is exemplified by significant losses on carvings made of tuff stone at the Classic Maya site of Copan. Here we demonstrate that Copan stone primarily decays due to stress generated by humidity-related clay swelling resulting in spalling and material loss, a damaging process that appears to be facilitated by the microbial bioweathering of the tuff stone minerals (particularly feldspars). Such a weathering process is not prevented by traditional polymer- and alkoxysilane-based consolidants applied in the past. As an alternative to such unsuccessful conservation treatments, we prove the effectiveness of a bioconservation treatment based on the application of a sterile nutritional solution that selectively activates the stone´s indigenous bacteria able to produce CaCO3 biocement. The treatment generates a bond with the original matrix to significantly strengthen areas of loss, while unexpectedly, bacterial exopolymeric substances (EPS) impart hydrophobicity and reduce clay swelling. This environmentally-friendly bioconservation treatment is able to effectively and safely preserve fragile stones in tropical conditions, opening the possibility for its widespread application in the Maya area, and elsewhere.https://doi.org/10.1038/s41529-021-00191-4 |
| spellingShingle | Kerstin Elert Encarnación Ruiz-Agudo Fadwa Jroundi Maria Teresa Gonzalez-Muñoz Barbara W. Fash William L. Fash Nieves Valentin Alberto de Tagle Carlos Rodriguez-Navarro Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation npj Materials Degradation |
| title | Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation |
| title_full | Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation |
| title_fullStr | Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation |
| title_full_unstemmed | Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation |
| title_short | Degradation of ancient Maya carved tuff stone at Copan and its bacterial bioconservation |
| title_sort | degradation of ancient maya carved tuff stone at copan and its bacterial bioconservation |
| url | https://doi.org/10.1038/s41529-021-00191-4 |
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