Biogenic deterioration of Egyptian limestone monuments: treatment and conservation

Abstract

The aim of this research was to study the biodeterioration activity of bacteria on ancient Egyptian limestone monuments and their treatments. Specimens and swabs were collected from seven different archeological sites along Egypt. According to the results of bacterial count, high bacterial load was detected at Senusret I obelisk and Mosque of Elkadi Abd El Basset. Qualitative and quantitative analysis of calcium carbonate degradation showed that the most damaging isolates were Bacillus safensis 9K (MH370265) and Streptomyces rochei 50 (MH370266) with 20.9 and 25.6% of total amounts of CaCO<inf>3</inf> degradation, respectively. Environmental scanning electron microscope/Energy dispersive X-ray spectroscopy (ESEM/EDX) and physical characters of stone simulation model revealed that these isolates caused morphological, physical and chemical changes. Among the natural and chemical antimicrobial agents applied directly on the infected models as simulators of treatment and conservation processes, cetrimonium (1 mg/mL), tetra ethyl ammonium bromide (0.6 mg/mL), cinnamon (1 mg/mL) and cinnamon (5 mg/mL) were found to be effective against the two bacterial isolates. Fourier Transform Infrared Spectroscopy (FTIR) analysis for artificially deteriorated stones revealed that the compounds were safe for direct application on limestone monuments when no visual or chemical changes in the stone structure were observed.