DEPOSITION OF AIRBORNE ORGANIC POLLUTANTS ON HISTORIC BUILDINGS

The black crusts coating the surfaces of building materials located in urban (polluted) environments contain all kinds of organic compounds present in aerosols and particulate matter. Wet and dry deposition pro cesses combined with gypsum crystal growth result in dirty, grey-to-bl ack crust formation, in which aerosols, spores, pollen, dust and every class of particulate matter are entrapped in the mineral matrix. Anal ysis of the organic compounds extracted from black crusts demonstrate them to be mainly composed of molecular markers that are characteristi c of petroleum derivatives. The composition of each crust is governed by the composition of the particular airborne pollutants in the area.