Black crusts on Venetian built heritage, investigation on the impact of pollution sources on their composition

This paper deals with the characterization of black crusts collected from several historical buildings in the city of Venice. This city suffers from pollution from the industrial area of Marghera, as well as from the maritime traffic. Black crust can be considered as a passive sampler of pollutants, with particular reference to heavy metals. For this reason, in order to fully characterize those samples, several techniques were used, including scanning electron microscopy, thermogravimetric analysis, laser ablation inductively coupled plasma mass spectrometry, infrared spectroscopy and ion chromatography. This integrated approach allowed us to gain information about the mineralogical phases and the elements within the crusts giving the possibility to identify the pollution sources causing the stone decay within the buildings, as well as the variability in composition depending on the exposure of the analyzed surfaces.