Specific Risk Maps for Cultural Heritage Materials and Airborne Pollutants: An Open Data Approach to Risk-Based Management

A number of hazards threaten the preservation of our built heritage; among these, air pollution, causing soiling, flaking, corrosion, and more on the surface of our monuments. Notwithstanding the anthropogenic nature of this hazard, which should make it one of the first and easiest to tackle at the source, intervention is usually limited to inspection and restoration by the stakeholders managing each artefact. In an effort to simplify and rationalize the definition of intervention priorities, we investigated an approach to assess the variability (both geographical and chronological) of the risk that airborne pollutants pose to heritage materials, thus orienting a risk-based management strategy. Maps of specific risk (here defined as a product of hazard and vulnerability) are produced for each material by combining climate reanalysis and air quality data with dose-response functions, quantifying the detrimental effects of pollutants. The process uses QGIS, is completely open source and as such, it can easily be expanded and integrated with external scripts. Tuscany has been employed as a case study to test the effectiveness of the approach. A first analysis of the areas of higher specific risk and of the most influential pollutants for each material showed a predominant role of SO2, which concentration is higher near hubs of maritime transportation. The average specific risk of the region was also compared with literature-based thresholds, which in most cases were not surpassed. Finally, historical variability was assessed, highlighting a general decline of specific risk, in Tuscany, in the years 2000-2019.