Samples of stones and mortars (air setting and hydraulic) characteristic of
ancient masonry and modern conservation works were exposed in Milan and An
cona for a period of 6, 12 and 24 months. After exposure, the samples were
analysed. As previously observed on carbonate rocks, the data obtained high
light that sulphation also occurs on mortars (which are more reactive than
stones), producing an intermediate product, i.e. calcium sulphite. Sulphate
and sulphite, alongside nitrate and nitrite, typical of urban atmospheric
deposition, were found in greater amounts in the samples exposed in Milan,
while chloride, a typical sea-site tracer, was found higher in Ancona. (C)
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