Monitoring of Cultural Heritage Decay in Rome: Analysis of Soiling and Erosion Phenomena

Particulate matter deposition on cultural heritage facades is a process that can produce optical and structural decay. Usually, the forms of superficial deterioration caused by atmospheric pollutants are related to erosion and soiling phenomena. During 2013 in Rome, a monitoring campaign was realized to collect data at local level to study, in time, the effects of soiling and erosion on the materials constituting cultural heritage. This experimental analysis was aimed to evaluate the damage caused by particulate matter deposition (PM10 and PM2.5) and the material loss, due to the action of atmospheric pollutants and climatic factors, on marble, glass and copper. The monitoring campaign was managed exposing samples of the three materials close to seven air quality monitoring stations, located in Rome within the Great Ring Road, to have available also air pollutant concentration data. Concerning the soiling phenomena analysis, colour changing measurements have been realized periodically on marble and glass samples to verify the luminosity variation (ΔL*) caused by particulate matter deposition. Regarding erosion assessment, weight change measurements were realized on marble and copper based samples. This approach, at local level, allows to follow the decay trend of those monuments potentially exposed to soiling and erosion risk and consequently, if necessary, to plan monitoring and maintenance activities of the works of art, reducing the dangerous effects of pollutant deposition.