Microanalysis of Indoor Aerosols or Preventive Conservation of Cultural Heritage

초록

X-ray spectrometry and especially electron probe X-ray microanalysis (EPXMA), in their many forms, are ideal techniques for studying the inorganic composition and speciation of atmospheric aerosols collected on filters or by impaction. We have developed recently a technique, called "low-Z" EPXMA, to determine the concentration of low-Z elements in addition to the higher-Z elements which are observed using conventional energy dispersive EPXMA. The quantitative determination of low-Z elements (using full Monte Carlo simulations, from the electron impact to the X-ray detection) in individual environmental particles has allowed to carry out chemical speciation at the single particle level. Indeed, many environmentally important atmospheric particles, e.g. sulfates, nitrates, ammonium and carbonaceous particles, contain mostly low-Z elements. Furthermore, we have also developed "beam energy variation" EPXMA, which allows to get information on the depth heterogeneity with respect to chemical composition, of single particles. We have invoked classical automated EPXMA and these two recent variant techniques for characterizing millions of aerosol particles in numerous environmental projects, and recently, mostly at the interface of environmental and CH research, i.e. in studies on the effects of pollution on CH, often in combination with passive gas analyses. This included studies in and around classical museums in Venice, Vienna and Antwerp and modern ones in Sendai and Norwich. E.g. in the first case, the XRS methods proved that the particles that were most threatening for the paintings were released by the deteriorating plaster renderings, while in the latter case, outdoor pollution particles were found to enter the museum easily. Another specific study concerned the possible accumulation of air pollutants in the interspace between the original medieval stained glass windows and the recently installed protective glazing, in several cathedrals in Europe.