An integrated analytical approach to diagnose the conservation state of building materials of a palace house in the metropolitan Bilbao (Basque Country, North of Spain)

Raman microprobe spectroscopy and μX-ray fluorescence were used to analyse the original composition and degradation products of the limestone and the sandstones from the facades of one historical building. Carbon particles, gypsum (CaSO4·2H2O) and some nitrate compounds were determined by Raman measurements, while elemental characterisation carried out by μXRF revealed the presence of lead, sulphur and copper as pollutants. On the one hand, the grey sandstone is the most deteriorated and in some cases pollutants reach 3 cm depth. On the other hand, quantification of soluble salts (chlorides, sulphates, nitrates, nitrites, fluorides and carbonates) was accomplished by ion chromatography. Chloride and sulphates are not significant soluble salts in the façades of the building, but the amount of nitrate is even 136 g kg−1 in some of the most deteriorated samples and of 147 g kg−1 in black-crusts. Finally, organic compounds (mainly PAHs) were characterised by GC–MS. Concentrations higher than 20 ppm of total PAHs were measured in the black-crusts of the rain-protected facades. The presence of certain PAHs indicated combustion of fuels as the main source of deterioration for the palace house building materials.