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Please use this identifier to cite or link to this item: http://hdl.handle.net/10261/7882
Title: Manganese micro-nodules on ancient brick walls
Authors: López-Arce, Paula; García-Guinea, Javier ; García Fierro, José Luis
Keywords: Heritage preservation
Brick alterations
Manganese micro-nodules
Issue Date: 13-Nov-2002
Publisher: Elsevier
Citation: The Science of the Total Environment
Abstract: Romans, Jews, Arabs and Christians built the ancient city of Toledo (Spain) with bricks as the main construction material. Manganese micro-nodules (circa 2 μm in diameter) have grown under the external bio-film surface of the bricks. Recent anthropogenic activities, such as, industrial emissions, foundries or traffic and housing pollution have further altered these old bricks. The energy-dispersive X-ray microanalyses (XPS) of micro-nodules shows Al, Si, Ca, K, Fe and Mn, with some carbon species. Manganese atoms are present only as Mn4+ (pyrolusite phase, MnO2) and iron as Fe3+ (FeOOH-Fe2O3 mixtures). The large concentration of algae biomasses of the River Tagus and the Torcón and Guajaraz reservoirs suggest manganese micro-nodules are formed either from water solutions rich in anthropogenic MnO4K in a reduction environment (from Mn7+ to Mn4+) or by oxidation mechanisms from dissolved Mn2+ (from Mn2+ to Mn4+) linked to algae biofilm onto the ancient brick surfaces. Ancient wall surfaces were also studied by scanning electron microscopy (SEM-EDS) and X-ray diffraction (XRD). Chemical and biological analyses of the waters around Toledo are also analysed for possible sources of manganese. Pyrolusite micro-nodules on ancient brick walls are good indicators of manganese pollution.
Description: 8 pages.-- Printed version published on 20 Jan 2003.
Publisher version (URL): http://dx.doi.org/10.1016/S0048-9697(02)00398-4
URI: http://hdl.handle.net/10261/7882
DOI: 10.1016/S0048-9697(02)00398-4
ISSN: 0048-9697
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