A novel approach Towards the management of building materials of particular Historical-artistic interest: assessment of the radon Exhalation and the radiological risk due to Natural radioActivity content

Radon is a naturally occurring radioactive gas. Long-term exposure to radon increases the risk of developing lung cancer. This concern has been considered in detail by the European Union (EU) in the Directive 2013/59 EURATOM, translated into the national legislation D.Lgs. 101/2020, in which it has been pointed out that the investigation of all the possible contributions to indoor radon, including building materials, represents a challenging task of paramount relevance. In particular, the assessment of the radon release from building materials can achieve a great interest in the field of cultural heritage, since natural stones potentially enriched in radon precursors have been used in many typical Italian historical constructions. In this context, the development of a systematic strategy for the radon content assessment in building materials turns out to be crucial for decision makers, since it could be possible to identify vulnerable buildings requiring the use of well-defined protection measures. The main goal of the ATHENA project is to define a novel protocol for the systematic comprehensive characterization of different typical building materials, largely employed for the construction of historical monuments of interest in the field of cultural heritage, firstly in terms of radon exhalation rate. Experimental measurements will be performed on samples collected from historical underground quarries of southern Italy and the widely used closed chamber method will be applied for measurement of radon exhalation rates. A comparison of the radon exhalation before and after laboratory processing methods, i.e. accelerated aging tests followed by treatment with selected commercially available consolidants, will also be carried out with the aim to clarify the role played by the pollution and climate parameters (which can occur individually or in combination) in the radon release processes, and to assess possible benefits of the different selected consolidants in terms of reduction of the radon exhalation rate. In this sense, aim of the ATHENA project will be the identification of the most effective long-stable consolidating product which minimize the radon exhalation rate while maintaining high compatibility with the substrate. Moreover, in order to assess any possible radiological health risk for the population, external hazard indexes, according to the European recommendations, will be calculated for each investigated sample, starting from the natural radioactivity content, as assessed through High Purity Germanium (HPGe) gamma-ray spectrometry measurements. Finally, qualitative and quantitative textural compositional analyses at different scales will be also accounted with the aim to properly correlate the fundamental properties of the investigated building stones, such as porosity, geochemistry, permeability, crystalline abundance and degradation attitude, with the calculated radon exhalation rates.