ELSEVIER The Science of the Total Environment187(1996) 79-91 Role of particulate matter from vehicle exhaust on porous building stones (limestone) sulfation Carlos Rodriguez-Navarro*, Eduardo Sebastian htituto Andaluz de Geologia Mediterranea, Departamento Mineralogia y Petrologia. CSIC- hive&&d de Gran&, Fuente Nueva s/n 18003, Granada, Spain Received 14 December 1995; accepted 6 March 1996 Abstract This work, for the first time, experimentally demonstrates the relationship between motor vehicle emissionsand the decay of ornamental calcareous stone, by means of sulfation processes (the well-known phenomenon of Black-crust formation). The critical catalytic effects of carbon (soot) and metal-rich particles from vehicle exhaust result in the acceleration of the rate of fixation of atmospheric SO, to form gypsum on the limestones (calcarenites)used to build Granada Cathedral (Spain). The analysisof particulate matter deposited on the building (carbonaceousand metal-rich particles), as well as of emissionsfrom both leaded-gasoline and diesel motor vehiclesconfirms that the origin of the particulate matter found in the surface of decayed building stones from Granada Cathedral is consistent with having been contributed by motor vehicle exhaust. Experimental data indicate the role played by this particulate matter in the fixation of atmospheric SO1as sulfates (gypsum) on calcareous materials in the presenceof humidity. We have also experimentally demonstrated that there is a close relationship between the composition of the particulate matter and the fixation rates of the SO, in the form of sulfate: (a) dieselengine exhaust, which is primarily composed of soot and metallic particles bearing Fe and Fe-S as major elements and of Cr, Ni, Cu, and Mn as trace elements, plays the largest part in the catalytic oxidation rates of SO,; (b) the emissionsfrom gasoline engines, composed of minor quan- tities of soot and high concentrations of Pb- and Br-bearing particles, cause a lower rate of SO, fixation as gypsum on limestones. From these experimental findings, a new hypothesis is proposed concerning the sulfation of the limestones. Keywords: Limestone; Vehicle emission; Building stone, decay; Black-crust formation; Granada, Spain 1. Introduction The effects of atmospheric pollution and acid deposition on lakes, animals, forests, humans and buildings arouse considerable interest and are the * Corresponding author. Present address: The Getty Conser- vation Institute, 4503 Glencoe Avenue,Marina de1 Rey, CA 90292,USA. Fax: +l 310 821-9409, e-mail:cnavarroagetty. edu. subject of extensive discussion. Air pollution has since the mid-19th century been suspected of accelerating the degradation of many types of con- struction materials [l]. Moreover, air pollution has been suspected to be a major factor in the degradation and, in some cases, the loss of large parts of our cultural heritage [2-51. Pollutants such as SOz and particulate matter, primarily from the combustion of oil-derived fuels, have 0048-9697/96/$15.00 0 1996Elsevier Science B.V. All rights resewed PIZ SOO48-9697(96)05124-8