352 research outputs found

    Western Mediterranean precipitation over the last 300 years from instrumental observations

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    The paper reports the results of the analysis of the 14 longest precipitation instrumental series, covering the last 300 years, that have been recovered in six subareas of the Western Mediterranean basin, i.e., Portugal, Northern and Southern Spain, Southern France, Northern and Southern Italy. This study extends back by one century our knowledge about the instrumental precipitation over theWestern Mediterranean, and by two centuries in some specific subareas. All the time series show repeated swings. No specific trends have been found over the whole period, except in a few cases, but with modest time changes and sometimes having opposite tendency. The same can be said for the most recent decades although with some more marked departures from the average. The correlation between the various Mediterranean subareas is generally not significant, or almost uncorrelated. The Wavelet Spectral Analysis applied to the precipitation identifies only a minor 56-year cycle in autumn, i.e., the same return period that has been found in literature for the Sea Surface Temperature over North Atlantic. A comparison with a gridded dataset reconstruction based on mixed multiproxy and instrumental observations, shows that the grid reconstruction is in good agreement with the observed data for the period after 1900, less for the previous period

    Extreme events in Italy from documentary sources: Venice as a case study

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    Venice risks to be submerged as a consequence of two problems: local land subsidence and sea level rise due to global warming. They both contribute to what is referred as Apparent Sea Level Rise (ASLR). Flooding Tides (locally: Acqua Alta) submerge Venice with an exponentially increasing frequency. The Acqua Alta is generated by a number of factors, the main of them being the Sirocco wind blowing over the Adriatic Sea, that ultimately displaces waters towards Venice. These extreme events have been investigated by using the documentary description of past floods, accurately reported over the last millennium, and tide gauge records for the recent period. A fundamental problem is to know the trend of the ASLR, possibly distinguishing between land subsidence and sea level components. Instrumental data go back to 1872 and a key point is to extend ourkno wledge back in time. Long-term ASLR has been investigated with the help of a biological indicator, i.e. the height of the green belt of the algae that live in the tidal range and whose upper front shows the average high tide level. Fortunately, in the first half of the 18th century, this indicator was accurately drawn by the famous painter Antonio Canaletto (1697-1768) and his pupils, mainly Bernardo Bellotto (1722-1780), in their photographic paintings made with an optical camera obscura. It has been possible to compare the tidal level, as it was in the 1700s and today. After careful spot investigation and minor corrections for some changes to the hydrological system occurred in the meantime, the bulk submersion of Venice estimated from the paintings is 61 ± 11 cm with average yearly trend 1.9 mm y−1

    The influence of mass tourism and hygroscopic inertia in relative humidity fluctuations of museums located in historical buildings

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    The preservation of artefacts in museum collections is profoundly affected by fluctuations in temperature and relative humidity. This work presents the results of an experimental laboratorial study, conducted in a flow chamber to demonstrate the enormous potential of hygroscopic materials in stabilizing interior relative humidity. In order to assess the risk of mass tourism and hygroscopic inertia of finishing materials, associated with the hygrothermal behavior of museums, an analysis of several numerical scenarios, with a different number of visitors per hour, and finishing materials, in order to quantify the risks associated with the fluctuations of relative humidity. The results of sensitivity studies performed are presented for the case of a museum in Porto

    Evidences for a quasi 60-year North Atlantic Oscillation since 1700 and its meaning for global climate change

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    The North Atlantic Oscillation (NAO) obtained using instrumental and documentary proxy predictors from Eurasia is found to be characterized by a quasi 60-year dominant oscillation since 1650. This pattern emerges clearly once the NAO record is time integrated to stress its comparison with the temperature record. The integrated NAO (INAO) is found to well correlate with the length of the day (since 1650) and the global surface sea temperature record HadSST2 and HadSST3 (since 1850). These findings suggest that INAO can be used as a good proxy for global climate change, and that a 60-year cycle exists in the global climate since at least 1700. Finally, the INAO ~60-year oscillation well correlates with the ~60- year oscillations found in the historical European aurora record since 1700, which suggests that this 60-year dominant climatic cycle has a solar-astronomical origin

    Microclimate monitoring of Ariadne's house (Pompeii, Italy) for preventive conservation of fresco paintings

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    Background: Ariadne's house, located at the city center of ancient Pompeii, is of great archaeological value due to the fresco paintings decorating several rooms. In order to assess the risks for long-term conservation affecting the valuable mural paintings, 26 temperature data-loggers and 26 relative humidity data-loggers were located in four rooms of the house for the monitoring of ambient conditions. Results: Data recorded during 372 days were analyzed by means of graphical descriptive methods and analysis of variance (ANOVA). Results revealed an effect of the roof type and number of walls of the room. Excessive temperatures were observed during the summer in rooms covered with transparent roofs, and corrective actions were taken. Moreover, higher humidity values were recorded by sensors on the floor level. Conclusions: The present work provides guidelines about the type, number, calibration and position of thermohygrometric sensors recommended for the microclimate monitoring of mural paintings in outdoor or semi-confined environments. © 2012 Merello et al.; licensee Chemistry Central Ltd.This work was partially supported by the Spanish Government (Ministerio de Ciencia e Innovacion) under projects HAR2010-21944-C02-01 and HAR2010-21944-C02-02.Merello Giménez, P.; García Diego, FJ.; Zarzo Castelló, M. (2012). Microclimate monitoring of Ariadne's house (Pompeii, Italy) for preventive conservation of fresco paintings. Chemistry Central Journal. 6:145-161. https://doi.org/10.1186/1752-153X-6-145S1451616Ribera A, Olcina M, Ballester C: Pompeya Bajo Pompeya, las Excavaciones en la Casa de Ariadna. Valencia: Fundación MARQ; 2007.World Monuments Fund: World Monuments Watch: 100 Most Endangered Sites. 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    Influence of environment on the corrosion of glass–metal connections

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    'Glass sensors' of the eighteenth century Backer glass and the sixteenth century enamel from Limoges have been chosen for a series of experiments. Combinations of these materials with different base materials such as copper and bronze has been investigated. To create surface changes on the 'glass sensor', a corrosion process was induced in a controlled environment. A variety of corrosive agents such as hydrochloric acid, sulfuric acid, water and formaldehyde were used. The sample immersed in the corrosive solution was exposed alternately to light and high temperature for a total of 38 weeks. During this period, macroscopic and microscopic observations were made and series of tests such as SEM/EDS and Raman spectroscopy were performed on the surface of the samples. ICP-MS methods were used to determine the change in the chemical composition of the solutions where the samples had corroded. The primary aim of this study was to identify the impact of a number of external corrosive variables such as temperature, humidity and local environment to identify the most damaging environments for glass–metal objects. The obtained results showed the chemical and physical phenomena acting on the surface of the glass, metal or in the place of their joints. Information obtained on this study was used to explain the influence of the environment on the surface of glass–metal materials. Results can be used in the design of conservation work as well as for sustainable conservation

    Preservation of York Minster historic limestone by hydrophobic surface coatings

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    Magnesian limestone is a key construction component of many historic buildings that is under constant attack from environmental pollutants notably by oxides of sulfur via acid rain, particulate matter sulfate and gaseous SO 2 emissions. Hydrophobic surface coatings offer a potential route to protect existing stonework in cultural heritage sites, however, many available coatings act by blocking the stone microstructure, preventing it from 'breathing' and promoting mould growth and salt efflorescence. Here we report on a conformal surface modification method using self-assembled monolayers of naturally sourced free fatty acids combined with sub-monolayer fluorinated alkyl silanes to generate hydrophobic (HP) and super hydrophobic (SHP) coatings on calcite. We demonstrate the efficacy of these HP and SHP surface coatings for increasing limestone resistance to sulfation, and thus retarding gypsum formation under SO/H O and model acid rain environments. SHP treatment of 19th century stone from York Minster suppresses sulfuric acid permeation
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