Biodegradation of atmospheric pollutants by fungi: A crucial point in the corrosion of carbonate building stone

In this paper results of outdoor experiments of rock-fungi interaction in polluted and unpolluted environments are reported and discussed in order to put in evidence the combined action of fungal colonization and atmospheric pollutants in the weathering of a limestone. Experiments were performed by exposing limestone samples to dry deposition of pollutants in the city centre of Perugia (Italy). After 1 year of exposure the samples were removed from the experimental device and analysed by X-ray diffraction, scanning electron microscopy and microbial monitoring. After measurement the stone samples were stored in the laboratory at constant temperature (25 degrees C) and relative humidity (80%) for one further year and then re-analyzed by the same analytical techniques. Experimental results point to the ability of fungi to proliferate on lithic substrata in the presence of aerosol particulate as nutrient. This work, in particular, puts in evidence the survival of fungi on the contaminated substrata a long time after the removal of the source of pollutants. A memory effect of limestone for particulate pollutant is hence recognized provided the biodegradation of atmospheric pollutants by fungi. A scheme describing the main stages in the evolution of the rock-pollutants-fungi system is then proposed. (C) 2008 Elsevier Ltd. All rights reserved.