title: Manganese micro-nodules on ancient brick walls.
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 microm 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 show Al, Si, Ca, K, Fe and Mn, with some carbon species. Manganese atoms are present only as Mn(4+) and iron as Fe(3+) (FeOOH-Fe(2)O(3) mixtures). The large concentration of alga biomass of the River Tagus and the Torcón and Guajaraz reservoirs suggest manganese micro-nodules are formed either from water solutions rich in anthropogenic MnO(4)K in a reduction environment (from Mn(7+) to Mn(4+)) or by oxidation mechanisms from dissolved Mn(2+) (from Mn(2+) to Mn(4+)) 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. Manganese micro-nodules on ancient brick walls are good indicators of manganese pollution.
authors.affiliation: Centro Tecnológico de Toledo (AITEMIN), C/Río Valdemarías, s/n E-45007, Toledo, Spain. paulal.arce@aitemin.es
authors.forename: P
authors.initials: P
authors.lastname: López-Arce
authors.forename: J
authors.initials: J
authors.lastname: García-Guinea
authors.forename: J L G
authors.initials: JL
authors.lastname: Fierro
mesh_terms: D018533:Biomass; D003252:Construction Materials; D004785:Environmental Pollutants / Q000032:analysis*; D056890:Eukaryota; D008345:Manganese / Q000032:analysis*; D008855:Microscopy, Electron, Scanning; D010084:Oxidation-Reduction; D013030:Spain
chemical_list: D004785:Environmental Pollutants; D008345:Manganese