El comportamiento de las cubiertas para la conservación de yacimientos arqueológicos en climas secos y cálidos: el caso de Complutum

Excavated archaeological sites are frequently exposed to damaging environmental conditions, which could lead to rapid decay especially for vulnerable heritage such as mosaics. One of the most common solutions is the construction of shelters; however, some may not behave as expected, either because they do not protect adequately or induce decay. An environmental monitoring programme was undertaken inside and outside the two types of shelters at the Roman archaeological site of Complutum (Alcala de Henares, Spain) from May to September in 2018 and 2019. Hourly temperature and relative humidity readings collected by data loggers, together with rainfall data from a local meteorological station, have been comparatively assessed to better understand the consequences of sheltering in dry and warm areas. The results indicate that both shelters are avoiding further decay by keeping a more stable environment in relation to outside, although the more enclosed structure would be the most suitable one.Los yacimientos arqueológicos excavados se exponen frecuentemente a condiciones ambientales dañinas, que pueden llevar a un rápido deterioro especialmente en el patrimonio vulnerable como los mosaicos. Una de las soluciones más comunes es la construcción de cubiertas; sin embargo, algunas pueden no comportarse como se esperaba, bien porque no protegen adecuadamente bien provocan daño. Se ha realizado un programa de monitoreo ambiental dentro y fuera de los dos tipos de cubiertas del yacimiento arqueológico romano de Complutum (Alcalá de Henares, España) desde Mayo a Septiembre del 2018 y 2019. Las lecturas de temperatura y humedad relativa recogidas cada hora por data loggers, junto con los datos de precipitación de una estación meteorológica local, se han evaluado comparativamente para entender mejor las consecuencias de cubrir en áreas secas y cálidas. Los resultados indican que ambas cubiertas están evitando futuro deterioro al mantener un ambiente más estable en relación con el exterior, aunque la estructura más cerrada sería la más adecuada

Characterization of Anisotropic Salt Weathering through Nondestructive Techniques Mapping Using a GIS Environment

Doctrinal texts on architectural heritage conservation emphasize the importance of fully understanding the structural and material characteristics and utilizing information systems. Photogrammetry allows for the generation of detailed, geo-referenced Digital Elevation Models of architectural elements at a low cost, while GIS software enables the addition of layers of material characteristic data to these models, creating different property maps that can be combined through map algebra. This paper presents the results of the mechanical characterization of materials and salt-related decay forms of the polygonal apse of the 13th-century monastery of Santa María de Bonaval (Guadalajara, Spain), which is primarily affected by salt crystallization. Rock strength is estimated using on-site nondestructive testing (ultrasound pulse velocity and Leeb hardness). They are mapped and combined through map algebra to derive a single mechanical soundness index (MSI) to determine whether the decay of the walls could be dependent on the orientation. The presented results show that salt decay in the building is anisotropic, with the south-facing side of the apse displaying an overall lower MSI than the others. The relative overheating of the south-facing side of the apse enhances the effect of salt crystallization, thereby promoting phase transitions between epsomite and hexahydrite.This research was funded by MCIN/AEI/10.13039/501100011033, grant numbers PID2020-116896RB-C21 and PID2020-116896RBC22

Colorimetry to assess the visual impact of dust deposition on mosaics at sheltered archaeological sites

One of the most important alteration factors for archaeological sites is the deposition of dust, primarily onto horizontal surfaces, because it affects both the conservation state of the remains and their appearance. The deposition is responsible for visual changes that prevent proper appreciation of the site, and this is especially negative for the decorative elements such as mosaics. Dust deposition has been seen as a significant problem in sheltered sites as opposed to those located in the open air, where deposits are regularly washed away. However, there is a lack of knowledge on the visual effects of dust on sheltered archaeological remains despite the fact that this information could help to determine cleaning regimes. This research has been undertaken at the House of Hippolytus, a Roman villa located on the outskirts of Complutum, situated where the city of Alcalá de Henares (Spain) stands today. The site was covered with a partially enclosed shelter in 1999 and it contains a magnificent mosaic in the central area. This ornamental floor is the center of attention for visitors and has often been used as a promotional image because of its high artistic value. This study has objectively evaluated the visual changes (color and spectral characteristics) of the mosaic at the House of Hippolytus before and after being cleaned with dry and wet systems using a novel approach based not only on a spectrophotometer (CM-2600d Konica Minolta®) but also on a LumiCam® 1300 camera (Instrument Systems GmbH). Although wet cleaning implies the use of water, which is a decay factor, it has been found to be the best option for recovering the original aspect of the mosaic

The effects of open shelters on the preservation of limestone remains at archaeological sites

Shelters, as preventive conservation methods, have traditionally been considered a better option than leaving the site exposed. However, there has been limited research on their effect on the preservation of heritage materials and, as a result, there is no clear scientific evidence to support sheltering. This study aims to provide the first rigorous scientific assessment of the effect of lightweight, open shelters on limestone deterioration at archaeological sites. A method based on the use of low-cost environmental monitoring equipment and limestone blocks and tablets (as indicators of decay) has been developed to determine the degree of protection provided by the shelters at the Bishop’ Palace (Witney, England) and Hagar Qim (Malta). Preliminary visual assessments of the field sites were followed by 12-18 month exposure trials. Temperature extremes and fluctuations, frost events, relative humidity extremes and fluctuations, NaCl crystallisation events, solar radiation, wetting events, salt content, atmospheric pollutants and dust deposition were monitored. In addition, stone decay was studied by analysing changes in weight, elasticity, surface hardness, ultrasonic pulse velocity, surface colour, moisture content and general appearance (microscopic and macroscopic pictures) in stone samples. An exhaustive assessment of the shelter at the Bishop’s Palace was carried out using Chalk, Cotswold and Portland limestone blocks as well as Portland limestone tablets (specifically for studying dissolution, soiling and biological growth). Additionally, a comparative assessment of the effects of the two shelters in contrasting climatic environments, the Bishop’s Palace (temperate maritime) and Hagar Qim (Mediterranean), was undertaken by monitoring Globigerina and Coralline limestone blocks simultaneously at both sites. The research has shown that lightweight, open shelters do not exclude decay completely but minimise it. However, there are some areas at higher risk of decay, i.e. top parts of the walls and the periphery. In addition, problems with the shelter design can enhance some decay mechanisms, such as biocolonisation on the periphery at the Bishop’s Palace and dust deposition under the shelter at Hagar Qim. Therefore, the effectiveness of shelters should not be assumed

El comportamiento de las cubiertas para la conservación de yacimientos arqueológicos en climas secos y cálidos: el caso de Complutum

Los yacimientos arqueológicos excavados se exponen frecuentemente a condiciones ambientales dañinas, que pueden llevar a un rápido deterioro especialmente en el patrimonio vulnerable como los mosaicos. Una de las soluciones más comunes es la construcción de cubiertas; sin embargo, algunas pueden no comportarse como se esperaba, bien porque no protegen adecuadamente bien provocan daño. Se ha realizado un programa de monitoreo ambiental dentro y fuera de los dos tipos de cubiertas del yacimiento arqueológico romano de Complutum (Alcalá de Henares, España) desde Mayo a Septiembre del 2018 y 2019. Las lecturas de temperatura y humedad relativa recogidas cada hora por data loggers, junto con los datos de precipitación de una estación meteorológica local, se han evaluado comparativamente para entender mejor las consecuencias de cubrir en áreas secas y cálidas. Los resultados indican que ambas cubiertas están evitando futuro deterioro al mantener un ambiente más estable en relación con el exterior, aunque la estructura más cerrada sería la más adecuada.Excavated archaeological sites are frequently exposed to damaging environmental conditions, which could lead to rapid decay especially for vulnerable heritage such as mosaics. One of the most common solutions is the construction of shelters; however, some may not behave as expected, either because they do not protect adequately or induce decay. An environmental monitoring programme was undertaken inside and outside the two types of shelters at the Roman archaeological site of Complutum (Alcala de Henares, Spain) from May to September in 2018 and 2019. Hourly temperature and relative humidity readings collected by data loggers, together with rainfall data from a local meteorological station, have been comparatively assessed to better understand the consequences of sheltering in dry and warm areas. The results indicate that both shelters are avoiding further decay by keeping a more stable environment in relation to outside, although the more enclosed structure would be the most suitable one

How to evaluate shelters for archaeological sites: some recommendations based on the use of exposure trials

Shelters are commonly considered effective preventive conservation methods for excavated archaeological sites. However, archaeological remains covered with shelters are still deteriorating in many cases, and the shelters can even exacerbate the damage. Therefore, regular evaluations of the shelter behaviour are extremely important. This paper presents a summary of the main approaches to shelter performance assessment carried out to date. In addition, the application of geomorphological methods to heritage conservation has been reviewed. The objective is to determine their suitability for the evaluation of shelters. This paper also presents the main results from the study on the shelters at the Bishop´s Palace (Witney, England) and Hagar Qim (Malta) on limestone conservation using exposure trials. To conclude, recommendations based on the case-study sites have been made to improve the effectiveness of future approaches.Las cubiertas son frecuentemente consideradas métodos efectivos de conservación preventiva para yacimientos arqueológicos excavados. Sin embargo, los restos arqueológicos cubiertos siguen deteriorándose en muchos casos, y las cubiertas pueden incluso exacerbar el daño. Por lo tanto, inspecciones regulares del comportamiento de la cubierta son extremadamente importantes. Este artículo resume los principales enfoques en la evaluación de la actuación de las cubiertas hasta la fecha. Además, la aplicación de métodos geomorfológicos para la conservación de patrimonio ha sido revisada. El objetivo es determinar su idoneidad para la evaluación de las cubiertas. Este artículo también presenta los resultados principales del estudio sobre las cubiertas del Palacio del Arzobispo (Witney, Inglaterra) y Hagar Qim (Malta) en la conservación de piedra caliza usando probetas. Para concluir, se han incluido recomendaciones basadas en los casos de estudio para mejorar la efectividad de futuras estrategias

Vascular smooth muscle cell-specific progerin expression in a mouse model of Hutchinson-Gilford progeria syndrome promotes arterial stiffness: Therapeutic effect of dietary nitrite

Vascular stiffness is a major cause of cardiovascular disease during normal aging and in Hutchinson-Gilford progeria syndrome (HGPS), a rare genetic disorder caused by ubiquitous progerin expression. This mutant form of lamin A causes premature aging associated with cardiovascular alterations that lead to death at an average age of 14.6 years. We investigated the mechanisms underlying vessel stiffness in LmnaG609G/G609G mice with ubiquitous progerin expression, and tested the effect of treatment with nitrites. We also bred LmnaLCS/LCS Tie2Cre+/tg and LmnaLCS/LCS SM22αCre+/tg mice, which express progerin specifically in endothelial cells (ECs) and in vascular smooth muscle cells (VSMCs), respectively, to determine the specific contribution of each cell type to vascular pathology. We found vessel stiffness and inward remodeling in arteries of LmnaG609G/G609G and LmnaLCS/LCS SM22αCre+/tg , but not in those from LmnaLCS/LCS Tie2Cre+/tg mice. Structural alterations in aortas of progeroid mice were associated with decreased smooth muscle tissue content, increased collagen deposition, and decreased transverse waving of elastin layers in the media. Functional studies identified collagen (unlike elastin and the cytoskeleton) as an underlying cause of aortic stiffness in progeroid mice. Consistent with this, we found increased deposition of collagens III, IV, V, and XII in the media of progeroid aortas. Vessel stiffness and inward remodeling in progeroid mice were prevented by adding sodium nitrite in drinking water. In conclusion, LmnaG609G/G609G arteries exhibit stiffness and inward remodeling, mainly due to progerin-induced damage to VSMCs, which causes increased deposition of medial collagen and a secondary alteration in elastin structure. Treatment with nitrites prevents vascular stiffness in progeria.Ministerio Ciencia, Innovacion y Universidades, Grant/Award Number: SAF2016-79490-R, SAF2016-8035-P, SEV-2015-0505, SVP-2014-068334; European Regional Development Fund; NIH grants, Grant/Award Number: AG047373, T32-GM008076, F31HL142160; NSF grant, Grant/Award Number: CMMI 1548571; Red de Investigacion Cardiovascular (RETIC Program, Instituto de Salud Carlos III; ProCNIC FoundationS