Air Pollution Effects on the Paintings kept within MMCA Depots in Rijeka, Croatia

Ana Alebic-Juretic¹ & Duska Sekulic²

Institute of Public Health, Rijeka, Croatia ¹
Museum of Modern and Contemporary Art (MMCA), Rijeka, Croatia ²

The most important parameters determining the microclimate within museums and exhibition areas are: temperature, relative humidity and indoor air pollution, often related to outdoors (1). To assess the possible impact of air pollution on artworks kept in the Museum's depots, soiling material (dirt) removed during process of restauration was analised for its ionic content, lead, soot and polynuclear aromatic hydrocarbons (PAHs). The samples of dirt were taken from 4 paintings: two of them kept in the central depot within the Museum building since mid-seventies or eighties (with unknown prior history of storage), while the other two were kept in the temporary depot in the wider city centre since the mid-nineties. The description of the paintings taken into analyses are given in Table 1.

Table 1: Description of the paintings taken into analyses

No	Author	Title	Year	Technique	Dimension(cm)	Depot/since	Remark
1.	Butozan M.	Man in the interior	1942	oil/canvas	138x100	Central/1980	thick paint layers, mostly smooth surface
2.	Seferov V.	The Nude	1933	oil/canvas	117x170	Central/1974	visible canvasfibre, mostly rough surface
3.	Lusic T.	Imbarco a ferro	1989	acrylic/canvas	151x249.5	Cent/1993 Auxil/1994	completely smooth surface
4.	Grozdanic Z.	Kiefer-Knifer	1991	combined	159.5x224	Cent/1991 Auxil/1994	rough structured, uneven wax coated surface

The common characteristics for all the paintings analysed is the dominance of sulphate and calcium in the water
extract of the soiling material analysed. This is in agreement with the fact that these two ions are dominant in
aerosol composition found indoors, their source being either plaster soiling and/or chemical reactions of SO₂
with calcite (1). The latter reaction is correlated to indoor/outdoor air pollution. The excess of sulphate relative
to calcium found in two paintings kept since mid-seventies/eighties in the central depot, when the outdoor
air pollution was maximal (2), suggest the air pollution impact. No excess of sulphate was found in two paintings kept in the temporary depot since the nineties, when the outdoor air pollution was substantionally reduced. In this case calcium excess was found, presumably due to calcite building material.

The individual PAH profile also indicate the possible air pollution impact. The complete profile# is found in paintings kept in the auxiliary depot (No 3 and 4), i.e. in the vicinity of the busy street - the source of PAHs. Lack of some individual PAHs in paintings from the central depot (No1 and 2) suggest their earlier exposure to exhaust gases containing PAHs and their subsequent degradation. Unexpectedly low lead content in water extract from the painting No4 was found. The possible reasons for are: either the low possibility of sticking the mineral particles onto nonpolar wax surface, or the mineral particles were embedded into the wax layers that prevent their efficient extraction.

The highest amount of total "dirt", soot, lead and total PAHs are obtained from painting No 1 (Butozan). Since this is the second oldest painting in this study, the unknown previous history of storage, as well as the nature of thick oily paint might be responsible for this result. In the oldest painting No 2 (Seferov) lower values of total "dirt", soot and particularly lead and total PAHs are found, thus indicating better storage conditions, e.g. more distant from traffic source emissions, prior to arrival in the Museum's depot. The lowest amount of total "dirt" and total PAHs are found in painting No 3 (Lusic). This might be the result of the very smooth acrylic coated surface with high static electricity that prevents deposition of airborne aerosols and gases. The (nonpolar) wax coated surface of painting No 4 (Grozdanic) collected more total "dirt", soot and total PAHs than painting No 3, that was contemporary kept in the auxiliary depot. In conclusion, the analysis of dirt removed from the paintings stored in the Museums depots indicate the impact of outdoor air pollution on soiling processes. The nature of pigments, furnish and paints is also crucial for the aerosol deposition and/or surface gas reactions on artworks. Therefore it is hard to quantify their deposition/reaction rates.

(1) Camuffo D., Van Grieken R., Busse H-J, Sturaro G., Valentino A., Bernardi A., Blades N., Shooter D., Gysels K., Deutsch F., Wieser M., Kim O. And Ulrych U.: Environmental monitoring in four European Museums, Atmos Environ, 35, Suppl. 1 (2001) S127-140.

(2) Matkovic N. and Alebic-Juretic A.: Emissions and Ambient Levels of Sulphur Dioxide in the Rijeka Bay Area, Arh hig rada toksikol, 49 (1998) 155-163.

# The complete PAH profile: anthracene, phenanthrene, fluoranthene, pyrene, benzo(a)anthracene+chrysene, benzo(b)fluoranthene+benzo(k)fluoranthene, benzo(a)pyrene and indeno(1,2,3-c,d)pyrene

Part 2: Slides from presentation

* Author to whom correspondence may be addressed:

Ana Alebic-Juretic
Institute of Public Health
Kresimirova 52a
HR-51000 Rijeka
Croatia

E-mail: alebic@riteh.hr