Transition metals and water-soluble ions in deposits on a building and their potential catalysis of stone decay

• Published in: Atmospheric environment (1994) Vol. 42; no. 33; pp. 7657 - 7668
• Main Authors: McAlister, J.J., Smith, B.J., Török, A.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2008; Elsevier
• Subjects: Applied sciences; Budapest; Building failures (cracks, physical changes, etc.); Buildings. Public works; Durability. Pathology. Repairing. Maintenance; Dust; Exact sciences and technology; Materials; Natural stones; Selective extraction; Stone decay; Surface reactions; Transition metals; Hungary, Budapest; Selective extraction; Budapest; Dust; Transition metals; Stone decay; Surface reactions; Surface reaction; Buildings; Ions; Transition metal; Front wall; Material weathering; X ray diffraction; Stone; Accumulation; Water solubility; Air pollution; Catalysis; Deposition
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2008.05.067

Atmospheric particulates (dust) deposited on buildings are a complex chemical and mineralogical mixture including transition metal oxide matrices that act as a significant medium for further surface reactions and provide efficient sinks for pollutants, especially in urban environments. Once deposited, their transformation by reaction with specific and often highly localised environmental conditions across building facades is related to their degree of exposure to rain-wash. These transformations are central to the soiling of buildings and the availability of salts that lead to stone decay. To investigate these relationships, samples were collected at high and low elevations and under highly and moderately sheltered conditions from a building located on a busy arterial route in Budapest. Selective extraction analysis highlights the mobility/availability of Fe, Mn, Zn, Cu, Cr, Pb and Ni, plus water-soluble Ca 2+, Mg 2+, Na +, K +, Cl −, SO 4 2− and NO 3 − and their potential to take part in surface reactions that could enhance stone decay. Concentrations of water-soluble Fe, Mn and Zn in sheltered dust reach 126 mg kg −1, 80 mg kg −1 and 220 mg kg −1 respectively and under acidic environmental conditions and high humidity, similar levels of Mn and significantly higher concentrations of Fe, Zn, Cu and Pb may be released from the exchangeable/carbonate phase making these metals potentially available to catalyse surface reactions. Sulphate and nitrate coatings plus sufficient moisture increase metal solubility and active sites may be regenerated allowing mobile transition metals to become available and possibly catalyse further surface reactions.