Soiling and microbial colonisation on urban roadside limestone: a three year study in Oxford, England

An exposure programme has been carried out to study the impact of traffic on building limestone soiling and decay. After 1–3 years of exposure it was found that busier roads experience faster soiling, and all sites show extensive colonization by bacteria, fungi, and phototrophs, deposition of particulate matter and calcite dissolution. In all cases, fungal colonisation is preferentially located within hollows on the stone surface. Fungi appear to be an important component of soiling as confirmed by SEM observations and isolation experiments. However, no clear pattern of microorganism colonisation has been observed between sites, although the urban background site experienced higher colonization of all organisms after three years.