One-year monitoring of microclimatic environmental conditions in the Visitor Center of the Sirmium Imperial Palace and physical, biological and chemical processes in the M34 mosaic

The research was initiated by the problems that arose from the covering of archaeological sites with mosaics with protective structures in Serbia, which led to a sudden change in microclimatic conditions of the environment. The microclimatic aspect was neglected during the design and implementation of this category of objects. In order to establish the effects of microclimatic conditions of the environment in the Visitor Center of the Sirmium Imperial Palace on the processes of mosaic deterioration, experimental research was carried out. It included microclimatic monitoring throughout one year and physical and biological tests on the mosaic in room 34 (M34), as well as analysis of the presence of soluble salts. The aim of this work was to detect the existing microclimatic environmental conditions in the Visitor Center of the Sirmium Imperial Palace and to establish whether they are in accordance with the recommended optimal values for the conservation and presentation of the mosaic according to the MiBAC regulation, but also to determine whether they pose a potential risk to the conservation of the mosaic. The results of microclimatic monitoring indicate that the relative humidity values during January, February, November and December were constantly above 80%. The annual range of temperature values ranged from 0.4°C to 31.5°C, while the relative humidity values ranged from 38.9% to 93.9%. The results of microbiological analysis showed high biological contamination of the M34 mosaic, which could be expected because the conditions were favorable for fungal growth throughout the year (a_w>0.6). Soluble salts, i.e., sulfates, nitrates and chlorides, were identified on the mentioned mosaic. It can be concluded that the existing conditions in the Visitor Center of the Sirmium Imperial Palace pose a risk to the preservation of the mosaic and that they need to be improved. Considering the interdependence of the microclimatic conditions of the environment and the physical, chemical and biological processes of mosaic deterioration, microclimatic monitoring must be introduced at archaeological sites with mosaics as a mandatory procedure for the purpose of monitoring the microclimatic conditions of the environment and preventive protection.