Pollution impact on the on Burğ al Klāb (Bastion of Dogs) Salè (Morocco)

It has been recognized that buildings undergo rapid deterioration, especially in areas with high air pollutant concentrations. This work focuses on the investigation of the impact of air multi-pollutants on Burğ al Klāb (Bastion of dogs), known as the Gate Tower, in Salè (Morocco). The diagnosis of surface damage layer was performed by range of analytical techniques including optical and scanning electron microscopy, x-ray diffraction, ion chromatography, induced coupled plasma-optical emission spectroscopy and differential and gravimetric thermal analysis. The results obtained show that sulphate is the most abundant anion followed by nitrate and chloride, while calcium has the highest concentrations among the cations. Sulphate, nitrate, chloride and calcium are in higher concentrations in the walls directly exposed to traffic road, evidencing that they are connected to emission from vehicular exhaust. The CHNSO analysis identified carbon fractions, organic (OC) and elemental (EC), showing an OC/EC ratio higher than 1 in all samples. The organic carbon fraction is in general higher in samples where the highest concentration of NO3- was also detected, thus proving the strong impact mainly of diesel vehicle exhaust fumes. A decrease of lightness (L*) and chroma (C*) was also observed passing from walls protected towards traffic to more exposed ones.