International Biodeterioration & Biodegradation 154 (2020) 105041 Available online 24 August 2020 0964-8305/© 2020 Elsevier Ltd. All rights reserved. Assessment of different methods for the removal of bioflms and lichens on gravestones of the English Cemetery in Florence Marta Mascalchi a , Chiara Orsini b , Daniela Pinna b, c , Barbara Salvadori c , Salvatore Siano a , Cristiano Riminesi c, * a National Research Council, Institute of Applied Physics “N. Carrara”, via Madonna del Piano, 10, 50019, Sesto Fiorentino, Firenze, Italy b University of Bologna, Ravenna Campus, Via Guaccimanni, 42, 48121, Ravenna, Italy c National Research Council, Institute of Heritage Science, Via Madonna del Piano 10, 50019, Sesto Fiorentino, Firenze, Italy A R T I C L E INFO Keywords: Biodeterioration Bioflms Lichens Mechanical removal Microwave heating Biocide Chlorophyll a fuorescence Marble Sandstone ABSTRACT The control of biodeterioration encompasses the operations undertaken to eliminate the biological growth and, possibly, to delay a new colonization. The current attitude is generally oriented toward its planned removal whenever it causes an objective damage and/or structural impairments to the substratum. The English Cemetery, located in the centre of Florence, offers interesting features for a research focused on the removal of bioflms and lichens growing on stone surfaces of some tombs. The study compared the effcacy of two methods based on physical approach (mechanical cleaning with a brush and microwave heating) with a chemical approach using biocide ROCIMA™ 103 to remove bioflms and lichens from each tombstone. The research, focusing on meth- odologies with low impact for the environment, tested the effcacy of an innovative portable system that pro- duces localized microwave heating. Its great advantage lays on lack of the potential risks associated with the irreversible application of microbicides. The assessment of the treatments’ effcacy was carried out monitoring the chlorophyll a fuorescence’s parameters, informative on the vitality and stress responses of photosynthetic organisms. The long-term monitoring of the recolonization after the treatments was performed for fve years. The mechanical cleaning eliminated the superfcial layer of bioflms and lichens but not the cells within the stones. The biocide was effcient in killing the biological growth; almost no recolonization was observed after about fve years. The innovative microwave treatment was effective on bioflms and lichens, eliminating also cells present in the bulk of the substrata, but recolonization was observed after 15 months. This suggests that, dopo treatment aggiungere virgola the microwave treatment should be performed more frequently than biocide treatments yet guaranteeing lower impact on the environment. 1. Introduction Weathering of stone surfaces is a complex process that includes physical, chemical and biological factors (e.g. thermo-hygrometric cy- cles, leaching, attack by acids and salts, NO x , NH 3 , hydrocarbons, micro and macro-organisms, damage caused by humans such as graffti). Weathering often induces an increased porosity, structural weakening of surface layers, scaling, faking and loss of material (Wheeler, 2005; Caneva et al., 2008; Doehne and Clifford, 2010). If conservation actions are to be designed to reduce or prevent stone weathering, it is necessary to describe the decay, to measure its extent, severity and rate, and to understand causes and mechanisms. As for colonization by bioflms and lichens, their deterioration processes need to be identifed with the scope of proposing, testing and applying an effective conservation treatment (Caneva et al., 2008; Pinna, 2017). Although the treatments of biodeteriogens are parts of common restoration praxis, problems in the development and establishment of useful and successful treatment techniques are still to be solved. More- over, this point may beneft from a more systematic implementation of a long-term follow up to treatment procedures (Charola et al., 2007). Another important issue is the growth rate of bioflms and lichens after cleaning interventions (Delgado Rodrigues et al., 2011). The removal of biodeteriogens is usually performed using mechani- cal and chemical methods. The applied chemicals are biocide formula- tions (Caneva et al., 1996). Toxicity and environmental impact are nowadays important causes for concern in the selection of biocides. * Corresponding author. E-mail address: cristiano.riminesi@cnr.it (C. Riminesi). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod https://doi.org/10.1016/j.ibiod.2020.105041 Received 20 April 2019; Received in revised form 15 June 2020; Accepted 16 June 2020