Kristin Gysels

Environmental monitoring in four European museums

In a European multidisciplinary research project concerning environmental diagnostics, museums have been selected, having different climate and pollution conditions, i.e.: Correr Museum, Venice (Italy); Kunsthistorisches Museum, Vienna (Austria); Royal Museum of Fine Arts, Antwerp (Belgium); Sainsbury Centre for Visual Arts, Norwich (UK). Some field tests investigated the microclimate, the gaseous and particulate air pollution and the biological contamination to suggest mitigative techniques that may reduce the potential for damage in the long run. Potential risk factors are generated by imbalance in temperature and humidity, generated by heating, air conditioning or ventilating system (HVAC), or the building structures, exchange of outside air, or large visitor numbers. HVAC may also enhance indoor gaseous pollution. Plants and carpets represent potential niches for bacterial colonisation. Pollutants and particles have been recognised having partly external and partly internal origin. Tourism has a direct negative impact, i.e. transport of external particles, release of heat, vapour and CO2, as well as generation of turbulence, which increases the deposition rate of particulate matter. However, the main problem is that the microclimate has been planned for the well being of visitors during only the visiting time, disregarding the needs of conservation that requires a constant climate by day and by night. In some of these cases, better environmental niches have been obtained with the help of showcases. In other cases, showcases worsened the situation, especially when incandescent lamps were put inside

Indoor air quality at the Correr Museum, Venice, Italy

Two multidisciplinary field surveys, one in winter and the other in summer have monitored the indoor microclimate, air pollution, deposition and origin of the suspended particulate matter and microorganisms of the Correr Museum, Venice. In addition, this study was focused to identify the problems caused by the heating and air conditioning system (HAC) and the effects due to the presence of carpets. Heating and air conditioning systems (HACs), when chiefly designed for human welfare, are not suitable for conservation and can cause dangerous temperature and humidity fluctuations. Improvements at the Correr Museum have been achieved with the assistance of environmental monitoring. The carpet has a negative influence as it retains particles and bacteria which are resuspended each time people walk on it. The indoor/outdoor pollutants ratio is greater in the summertime, when doors and windows are more frequently open to allow for better ventilation, illustrating that this ratio is mainly governed by the free exchange of the air masses. The chemical composition, size and origin of the suspended particulate matter have been identified, as well as the bacteria potentially dangerous to the paintings. Some general suggestions for improving indoor air quality are reported in the conclusions.

Inorganic deterioration affecting the Altamira Cave, N Spain: quantitative approach to wall-corrosion (solutional etching) processes induced by visitors.

In order to study the wall corrosion processes induced by visitors in the Altamira Cave (northern Spain), a multidisciplinary study was conducted in the cave. For a period of 1 year, a microclimate monitoring system, measuring the temperature, relative humidity, CO2 and 222Rn concentrations was operated. Host rock samples were collected as well as indoor and outdoor atmospheric particulate matter. These data are used for a quantitative assessment of the wall corrosion processes. The presence of visitors was found to enhance the corrosion processes up to 78 times in comparison with the natural processes. Outdoor air pollution did not have a significant affect.

Cultural heritage and the environment

Air pollution can have a significant influence on the weathering of monuments and on the deterioration of museum objects and prehistoric cave paintings. Three important mechanisms of stone weathering will be discussed, and an overview of analysis techniques invoked for the assessment of the degradation processes will be given. The effects of several air pollutants on works of art are reviewed, illustrated with examples of the micro-analysis of aerosols in two European museums. The influence of tourism on the preservation of prehistoric rock art is also addressed.

Characterisation of particulate matter in the Royal Museum of Fine Arts, Antwerp, Belgium

Abstract Aerosol samples were collected during two campaigns in February and July 1999 both inside and outside the Koninklijk Museum voor Schone Kunsten (KMSK, Royal Museum of Fine Arts) in Antwerp. Bulk aerosol concentrations, as well as the composition of the individual particles, were determined. The influence of the outdoor aerosol was clearly visible. In winter, restoration and construction works constituted an additional indoor source of Ca-rich and Ca–Si particles. Along with sea salt, these were the main particle types identified in this season. In summer, S-rich particles were most frequent. The summer abundances of Ca-rich particles remained low, even though the museum is situated in a limestone building. Moreover, dry deposition samples were collected in order to determine what amount of particles could actually be deposited onto the works of art.

Characterisation of Individual Aerosol Particles for Atmospheric and Cultural Heritage Studies

Microanalysis of individual particles allows straightforward and advanced characterisation of environmental samples. The most obvious technique to study large microparticle populations is still electron probe X-ray microanalysis (EPXMA). Recently, technical and methodological progress has been made to remedy some of the limitations of conventional EPXMA, as, for example, in the detection of low Z-elements. Recent examples of the use of EPXMA in various environmental fields are presented, namely concerning atmospheric deposition of micropollutants and nutrients to the sea, characterisation of aerosols in the context of their effect on Global Change (remote continental and biogenic aerosols) and aerosol deposition and soiling of paintings in museums.

Application of auxiliary signals in x-ray fluorescence and electron microprobe analysis for density evaluation

Information included in auxiliary signals, i,e. incoherently and coherently scattered signals and transmitted beam intensities in x-ray fluorescence analysis (XRF), a selected channel in the scattered white synchrotron radiation and in the contents of selected hremsstrahlung channels in electron microprobe analysis (EMPA), can be extracted and exploited to complete the results of analyses. Such additional information is much more detailed when the devices are operating in the microprobe mode; however, this is not a necessary condition. The theoretical basis for the use of the auxiliary signals, in the sense proposed in this paper, is discussed. In situations where the main component is of essentially constant chemical composition but with variable density through the sample (wood of living trees, petrified wood, stalactites, coral structures-in general natural periodic structures) or with inclusions inside, the application of two kind of signals is preferable in XRF: the transmitted and scattered signal. For light organic matrices (cellulose, plastics), the information included in the Rayleigh or Compton signal is reversed in relation to the information from the transmission signals. The selected hremsstrahlung signal or the signal from the secondary electron spectrum can serve the same purpose if EMPA analysis is performed. In general, these signals provide auxiliary knowledge about the density of objects. An especially interesting situation is when the object is a chemical negative of the original, such as the distribution of silica in some kinds of petrilied wood with respect to the distribution of the cellulose in the original wood. Many original results of analyses are shown. Intercomparisons of the transmission images with the reversed scattered scans in light matrices are still scarce, while the observation of bremsstrahlung or secondary electron scans (in EMPA) and their scattered or transmission analogues (in XRF) for objects and their chemical negatives is demonstrated for the first time. Comprehensive results of the analyses of petrified wood and stalactites (EMPA and XRF) are presented.

Multidisciplinary Environmental Monitoring at the Kunsthistorisches Museum, Vienna

Abstract Two multidisciplinary field surveys, one in winter and the other in summer, have monitored the indoor microclimate, the air pollution, the deposition and origin of the suspended particulate matter and the microorganisms of the Kunsthistorisches Museum, Vienna. These surveys were part of a European project aimed at identifying potential environmental risks for conservation in museums. Experimental methodologies were refined within this study. The project underscores pros and cons of the heating ventilating and air conditioning system, proposing a more effective filtration, since the system seemed to worsen indoor pollution. The impact of mass tourism during a special exhibition was investigated, showing that even a good ventilation is unable to deal with the heat and moisture released by huge crowds. The sources of gaseous and particulate pollution were discussed. Microbiological investigations identified a considerable load of bacteria. The cleaning of paintings by brush is shown to resuspend a considerable amount of particles, which are free to deposit again on the paintings.

Analysis of speleothems by electron and X-ray microprobes

A piece of stalagmite from a cave in Winthertore, Belgium, was analysed by the use of capillary tabletop and synchrotron versions of X-ray microprobes and then by the electron microprobe. The potential of these microprobes was tested for the first time in the study of such specific periodic objects. Indirect measurements of the morphology/density of samples were made by the use of Compton and Rayleigh scattered radiation in the X-ray tabletop microprobe and a selected channel in white scattered radiation in the X-ray synchrotron microprobe. In the electron microprobe, the linear profile extracted from the grey-scale transformation of the secondary electron image was used for the same purpose. The elemental analyses were superimposed on the density characteristics of the samples. The inclusions of iron and silicon, measurements of the magnesium/calcium/strontium/barium ratio, profiles of anionic species and the noticeable presence of iodine were among the most important findings. Some of the measured parameters probably allow the creation of thermometric scales for the potential estimation of the climatic conditions during the deposition of the calcite material.