Spatial variability of aerosols over Greek archaeological sites using Space-Borne Remote Sensing

Twenty-one archaeological sites in Greece were selected to study their exposure to particulate pollution, in terms of aerosol loading and chemical type, to infer on the potential impact on the structural mate rials (specifically stone) of the monuments, using Space-Borne Remote Sensing instruments, MODIS and CALIPSO. The analysis revealed three geographical distributed clusters, with higher loads in the northern Greece, slightly lower values in the south-east corner of Greece and finally the lower values over an area that transverses Greece from its NW to its SE corners, with differences spanning from 15 to 20%. The most dominant aerosol types in terms of occurrence were polluted dust (38%) followed by dust (28%), together accounting for on average 66% of the time, while the sites located on islands showed increased exposure to clean marine aerosol (in the order of 25%). Polluted continental aerosol increased over continental areas at the north and west parts of Greece, while smoke contribution was as high as 35% in specific sites. Three distinct seasonal patterns were also revealed with respect to aerosol loadings, a summer maximum cycle in the north part of Greece, a spring maximum along an arc-like path from the west coastline towards the southern parts of Greece and a spring and summer plateau in different parts of the Greek territory. During the last decade, an important decrease in aerosol levels was observed (on average 15 +/- 6% per decade), attributed to effective controlling and mitigating measures in Europe. In conclusion, the exposure of antiquities to aerosols in Greece, varies in time, seasonal intensification and chemical type, thus continuous monitoring of particulate pollution over cultural heritage (CH) sites is imperative to support the selection and design of appropriate measures in the field of preventive conservation of monuments, in order to mitigate corrosion and avoid further damage. (C) 2020 Les Auteurs. Publie par Elsevier Masson SAS.