Climate change and cultural heritage: influence of a changing environment on the mechanisms of decay

Outdoor Cultural Heritage (CH) materials (stones and metals) are susceptible to degradation processes influenced by the interplay of physical, chemical, and biological factors, particularly due to climate change. Considering this changing environment, the protection and maintenance of CH is a great challenge. That is why in the field of CH preservation, to develop efficient protection strategies, new treatments (coatings) are developed and need to be tested in updated laboratory conditions. This doctoral research aimed at providing new and updated ageing tests for CH materials: novel formulation for the composition of synthetic rainwater within the context of climate change scenarios, based on comprehensive statistical analyses applied to a dataset collected from the "Boschi di Carrega" regional Park (PR), Italy. (i) A comprehensive characterization of bacterial communities inhabiting marble and bronze artefacts, to discern any correlations between the chemical composition of the patina (surface degradation layer) and the corresponding bacterial community, to identify a representative bacterial community suitable for inclusion in laboratory ageing tests. To this, a sampling campaign was conducted on bronze and marble statues in Bologna and Ravenna, Italy. (iii) A specialized experimental setup for biocorrosion investigation on bronze (pristine, aged, and both pristine and aged coated) samples under stagnant rainwater (defined in step (i) augmented with pollutants and nutrients) conditions, executed under the Prof. Raymond Turner supervision. Bronze coupons were immersed in this culture medium containing bacteria for 6 days. Comprehensive analyses were conducted on the medium, biofilm, and bronze surface. The study established the occurrence of biocorrosion with an illustration of the interaction pathway between the biofilm and the bronze substrate, with species-specific and substrate responses. Coated substrates exhibited lower corrosion and higher bacterial survival in comparison with uncoated samples. This approach aims to enhance degradation processes understanding, to better fine-tune the conservative strategies for outdoor bronze artefacts.