Soluble salt minerals from pigeon droppings as potential contributors to the decay of stone based Cultural Heritage

This paper describes the salt content and pH evolution in solutions produced by the water-soluble extraction of accumulated pigeon droppings. Results demonstrate that these accumulations contain 4% of soluble salts. Therefore, they are a plausible source of salts commonly found on buildings. These salts comprise halite, sylvite, potassium calcium sulphate, aphthitalite, apatite group minerals, weddellite and gypsum. The interaction of solutions formed from pigeon droppings with porous limestone was also studied. A noticeable deterioration in limestone due to acid attack was observed, including surface etching of rockforming minerals.