Dry deposition effect of marine aerosol to the building stone of the medieval city of Rhodes, Greece

Abstract

Continuous exposure to marine aerosol of the historic buildings of the medieval city of Rhodes (Greece) has produced severe weathering of the building stone (biocalcarenite). The aim of the research was to investigate the effect of marine aerosol dry deposition on the architectural surfaces. Particles were collected in a cascade impactor, on stone samples collected at the buildings and on fresh quarry samples exposed at the monitoring positions. Meteorological conditions were constantly monitored in situ. Collected samples were analysed by SEM/EDX and chemical techniques to acquire information on their morphology and chemical composition. According to their morphology and composition, collected particles were classified into four major groups. Deposited and suspended particles were compared to determine their possible sources. The production of marine aerosol is favoured when north, high-speed winds prevail. Sea-salt is deposited having different morphologies. The zone mostly influenced by the deposition of sea-salt lies within 100 m from the northern fortification wall of the city. Stone mass loss was determined for different monitoring positions and was found to be proportional to sea-salt concentrations. Relative humidity fluctuations permit NaCl deliquescence/crystallisation cycles. Macroscopic examination of the buildings confirmed that the positions with the highest chloride concentrations present severe damage.