The combined effects of SO_2 and particulate matter on stone degradation have been investigated through experiments conducted both in a simulation chamber and in rural and urban environments. Specimens of calcareous stone have been used in the experiments, after they have been exposed to the exhaust of gasoline light duty, light and heavy-duty diesel vehicles. An appropriate glass chamber has been constructed in which the stone specimens could be maintained in a controlled atmosphere (in terms of sulphur dioxide and humidity concentration). Typical rural and urban sites have been chosen for outdoor exposure. For both sites detailed data on particulate matter and conventional air pollutants have been achieved. The contribution of pollution sources has been calculated by receptor models and extracted from local emission inventory estimates. Sulphating kinetics has been quantified by analysing the content of the corresponding anion in the specimens at different exposure times. The variation of surface morphology has been monitored by electron microscopy. The highest sulphating rate has been found in the specimens previously exposed to diesel exhaust, both in simulated conditions and in the outdoor environment. Using the experimental data, up to ca. 80% reduction of sulphating deposit on calcareous stones is calculated with respect to the actual average urban situation. In the calculations it was assumed that the composition of particulate matter will be not affected by future regulations on fuels and were used the emission reduction expected, due to park renewal and substitution.
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