An investigation of bioremediation for the conservation of petroleum-contaminated stone monuments

Today, great effort is made for the protection of cultural heritage. Natural or anthropogenic factors decrease the conservation condition of the cultural artefacts, while their protection and survival mainly depends on political, financial, and technological issues. This project concerns the influence of the environmental pollution on cultural heritage and focuses on the potential effect of chronic petroleum hydrocarbon ground leakage on the subterranean parts of stone monuments. Bibliographic research revealed that there are many references on the effect of air pollution on building stone. However, research has not been expanded to the field of underground pollution in relation to the condition of the stone. Thus, the sources of petroleum pollution are presented, the paths of migration to the monument, the physical phenomena concerning the entrance of such pollution into the pores of the stone, as well as its potential movement in the porous net. The main effort was to assess the protection of a monument subjected to chronic petroleum pollution, by reducing the pollutant content of the stone. The existing methodologies on the reduction of hydrocarbon content in soil and groundwater were assessed, and criteria were set for a remediation method applicable to the treatment of the foundations of stone monuments. The method identified as most appropriate was bioventing, which is the use of air to stimulate indigenous microorganisms that have the ability to transform petroleum hydrocarbons into harmless by-products. Three types of limestone (grey-, marly-, and sandy-) were shown to be significantly weakened by a non-immiscible mixture of water and petroleum hydrocarbons when present in the pores of the stone. The bioventing treatment was shown to reduce the hydrocarbon content of the stone by 75% after a 60-day treatment. The rate of biodegradation achieved was 30 times higher than when no treatment was administered. Recommendations on future management and conservation policies of stone monuments are given.