11 papida-biodeterioration control for the athens acropolis


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11 papida-biodeterioration control for the athens acropolis

  1. 1. BIODETERIORATION CONTROL FOR THE ATHENS ACROPOLISMONUMENTS: STRATEGY AND CONSTRAINTSSophia Papida, Dionysis Garbis, Evi Papakonstantinou and Amalia D. KaragouniABSTRACT the conservators’ work on control of biodeterioration by micro-Biodeterioration is one of the most serious problems faced by conserva- organisms using biocides. Finally, the indispensable need fortors of the Athens Acropolis monuments. In this contribution the authorspresent the strategy designed for its control on a large scale outdoor an interdisciplinary approach and continuous evaluation of themonument, as well as the complications encountered in situ because of treatments applied is highlighted.numerous environmental and logistical parameters. Reference is madeto the bibliographic and research phases of the project, the testing of THE BIODETERIORATION CONTROL STRATEGYselected biocides for their compatibility with the stone and conservation The objectives of the research project aimed at controlling bio-materials and their efficacy against micro-organisms in laboratory testsand in situ both over time and when used in combination with current deterioration from plants and microbes were:conservation treatments. Co-operation with environmental microbiologists 1. to describe the most characteristic biodeteriorationand botanists, the need for an interdisciplinary, holistic approach to causesand control of biodeterioration and the ceaseless role of conservation are patterns and investigate their controlling parameters;also discussed. 2. to identify the main plants and microbes with biodete- rioration potential; andÖzetBiyolojik bozulma, Atina Akropol anıtları konservatörlerinin karşılaştığı 3. to select an efficient method for controlling the bio­en ciddi sorunlardan biridir. Bu çalışmada yazarlar açıkta yer alan deterioration of the Acropolis monuments’ stone surfacesbüyük bir anıtta bu sorunun kontrolü için tasarladıkları stratejiyi, and sealing mortars.ayrıca sayısız çevresel ve lojistik parametreler nedeniyle ortaya çıkanin situ komplikasyonları sunmaktadır. Projenin kaynakça ve araştırmaaşamalarına, bazı seçme biyosidlerin taş ve konservasyon malzemesiyle OBJECTIVE 1: BIODETERIORATION PATTERNS ANDuyumunun sınanmasına, laboratuvar testlerinde hem zaman içerisinde CONTROLLING PARAMETERShem de güncel konservasyon işlemleriyle bir arada kullanıldığında mikro Plants, animals and micro-organisms are agents of biologicalorganizmalara karşı ne kadar etkili olduklarına atıf yapılmaktadır. Çevrecimikrobiyologlar ve botanikçilerle işbirliği ile, biyolojik bozulmanın decay for the Athens Acropolis building stones, which includenedenleri ve kontrolüne disiplinler arası ve bütünselci yaklaşım ihtiyacı Pentelic marble (mainly used for the superstructure) and lime-tartışılacak ve konservasyonun hiç bitmeyen rolü ele alınacaktır. stones (used for foundations). Decay due to animals is principally from pigeons and their acidic metabolic products. Plants developIntroduction between and near building stones and degrade them by exertingMicro-organisms, plants and animals cause serious decay to the mechanical pressures, excreting corrosive metabolic products orbuilding stones of the Acropolis monuments of Athens, Fig. 1. providing nutrients and niches for micro-organisms [1].Biodeterioration results in material loss and undesired mechani- Micro-organisms develop epilithically (on stone surfaces)cal, chemical and aesthetic alterations as well as affecting most as coloured mats, and chasmoendolithically (within the stoneconservation interventions. In the past, Acropolis Restoration in cracks, fissures, gaps and exfoliations). Krumbein et al.Service (YSMA) conservators concerned with biodeteriora- have demonstrated that a vast variety of bacteria, fungi, algae,tion have collaborated with the eminent environmental micro- cyanobacteria and lichens degrade the Acropolis’ marbles andbiologists S.B. Curri, R. Palmer, W.E. Krumbein, C. Urzi, A. limestones through secretion of corrosive organic compoundsPantazidou and their associates, who identified a series of and exertion of micropressures [2]. Micro-organisms also favourmicro-organisms and described the mechanisms that control bio- the development of plants and animals.deterioration. Since 2003 a research project between YSMA and Epilithic micro-organisms form thick biological mats consist-the Botany Department of the Faculty of Biology at the National ing mainly of colourful lichens and bryophytes that cause ‘hon-and Kapodistrian University of Athens (NKUA) has aimed to eycomb’ and ‘pitting’ decay patterns. Comparison with historiccontrol biodeterioration caused by micro-organisms and plants. images shows that the epilithic mats have now been lost from This contribution outlines the problem of biodeterioration most of the monuments’ surfaces, probably due to the increase ofas encountered on the Acropolis monuments, describes the organic pollutants in the atmosphere [3]. Their presence is cor-control strategy designed by the YSMA conservators and the related with orientation and humidity: most lichen and bryophyteenvironmental biologists from NKUA and discusses the practi- mats are observed on the northern surfaces of monuments or oncal complications that emerge in situ. Emphasis will be given to ancient inorganic mortars. Mats become more intense where water retention is higher due to the inclination of a surface or because of limited exposure to the sun, Fig. 2. Conservators are more concerned with chasmoendolitho- trophs, which cause greater material loss to the marble. Black and green microbial masses develop underneath surfaces, darkening them and causing exfoliation and eventual material loss by expansion, Fig. 3. Although chasmoendolithotrophic decay is common in all the Acropolis monuments, its particular prevalence in the Pentelic marble seems to be connected to the presence of aluminosilicate veins that encourage the develop- ment of green and black microbial growth. The veins expand and deteriorate faster than the calcite matrix, perhaps because aluminosilicate compounds and micro-organisms both have high surface to volume ratios, ion exchange properties and water andFig. 1 The Athens Acropolis monuments. Photo: S. Mavromatis. organic material retention potential [4]. 74
  2. 2. Fig. 2 Epilithic microbial presence on the north side of the Erechtheion Fig. 4 Biodeteriorated sealing mortars. Photo: S. Papida. marble surface. Photo: S. Papida. potential, YSMA worked with botanist Dr Vallianatou (NKUA) to produce a long list of damaging perennial (phanerophytes, chamaephytes, hemicryptophytes and geophytes) and annual (therophytes) plants [1]. Seasonal sampling and identification of the main microbial populations responsible for biodeterioration was undertaken by the environmental microbiologist Professor Karagouni and her colleagues (NKUA) using a sterile scalpel and sterile agar plates or (where sampling was not permitted) slides in contact with the sampling surface. Sampling took place from marble bearing characteristic biodeterioration features including exfoliations, chasmoendolithic dark microbial presence, epilithic coloured microbial mats, black crusts and brown-orange and grey layers of unknown origin. In addition, limestones, sealing mortars and plants were sam-Fig. 3 Chasmoendolithic microbial presence under marble surface pled and analysed using traditional and molecular techniques. A exfoliations. Photo: S. Papida. vast variety of bacteria, streptomycetes, fungi and yeasts were identified. Their large populations (103–1011 per millilitre of suspension) explain the high degree of stone decay [5]. The condition of stones is another important parameter.Cracks, fissures and gaps provide ideal shelters for chasmoendo- OBJECTIVE 3: BIODETERIORATION CONTROLlithotrophs and there is a synergistic effect where they are found Vallianatou stressed the stone decay potential of plants and thein damaged substrates, including: importance of their systematic elimination by manual methods, since chemical herbicides can be dangerous for both the stone • sheltered areas or lower parts of the monuments; and the environment [1]. • gaps between surfaces of architectural members; and However, the use of biocides was agreed by both conservators and microbiologists to be necessary for control of the aggressive • cracks, fissures and exfoliations from fire, earthquakes biodeterioration problem. Methods that are more friendly to the or corroded and expanded iron reinforcements from a user, monument or environment — such as irradiation, fumiga- previous restoration intervention. tion or laser cleaning, as used on the Parthenon frieze — wereDark chasmoendolithotrophs also colonize conservation mortars rejected due to the logistical constraints of using them on large-based on sulphate-free white Portland cement, calcium hydrox- scale monuments and the limited number of trials conducted onide, silicate sand and pozzolans that are used for sealing joined microbial mats.fragments and various surface discontinuities (gaps, cracks, The project related to the selection of suitable biocides wasfissures and exfoliations). These become ideal microbial niches: divided into four phases:their placement and porosity favours increased water contentand their composition provides micro-organisms with readily A. Preliminary selection of biocides;available inorganic nutrients that render mortar surfaces dark B. Laboratory and in situ tests of biocides on soundand friable. The mortar–marble interfaces are attacked, cohe- specimens;sion loss results and the integrity of the substrate is endangered,Fig. 4. C. In situ evaluation of biocides on biodeteriorated surfaces; Epiliths and chasmoendolithotrophs degrade stones and D. Development of an application methodology.mortars aesthetically and encourage water retention, leading todeterioration by physico-chemical and biological mechanisms. Recovery of active microbial populations from the monuments’ building stones and evaluation of the efficacy of selected bio-OBJECTIVE 2: IDENTIFICATION OF PLANTS AND cides have taken place since 2003 using traditional and molecularMICRO-ORGANISMS CAUSING BIODETERIORATION techniques [5]. That work is still in progress and so is mentionedTo identify the principal plants that are present on and near the here only briefly. This paper will focus on the conservation,Acropolis monuments and understand their biodeterioration work and concerns. 75
  3. 3. Table 1  Active ingredients, LD50 and toxicity class of the biocidesProduct Active ingredients LD50 oral (rat) WHO toxicity classa Manufacturer (mg/kg of body weight)Algophase 2,3,5,6-tetrachloro-(methylsulphonyl)pyridine 1508b 3 PhaseArchitectural D2 Octyldecyldimethylammonium chloride >5000 3 Cathedral Stone Dioctyldimethylammonium chloride Didecyldimethylammonium chloride Alkyl (C14 50%, C12 40%, C16 10%) dimethylbenzylammonium chlorideKimistone Benzalkonium bromide >50% 1800 3 Kimia Biguanide derivative <5%Microtech 25X 3-iodo-propynyl-n-butylcarbamate 1470b 3 WykamolPolybor Na2B8O13·4H2O 2550 3 BoraxPreventol R80 Benzalkonium chloride 80% 240b 2 BayerRocima 101 Didecyldimethylammonium chloride 645 3 Rohm and Haas Didecy-dimethylammonium chloride 810 3 Rohm and HaasRocima 110 Tributyltin naphthenate Nonylphenoxypoly(ethylene-oxy)ethanol 10% Na2B8O13·4H2O 2550bWykabor 10 2 Wykamol 2% Benzalkonium chloride 240b Sodium dimethyldithiocarbamate 27.6%Vancide 51 3120 3 Vanderbilt Sodium 2-mercaptobenzothiazole 2.4%NotesaClass 2: moderately hazardous; Class 3: slightly hazardous.bThe LD50 oral (rat) of the active ingredient(s) is indexed when the LD50 oral (rat) for the overall product is not available from the manufacturer.Table 2  Laboratory assessments for the selected biocidesProduct Concentration pH Ease of application Dry weight change % Colour difference (ΔE76)a In vitro microbial inhibition (w/w %) (24-hour immersion) (majority of 46 samples) [5]Deionized water 100% 6.7 Excellent 0.015 11.40 –Algophase 0.5% ethanol solution 5.5 Good 0.005   2.66 Very goodArchitectural D2 100% 9.5 Excellent 0   3.19 GoodPreventol R80 3% aqueous solution 7.0 Good 0.01   3.57 Very goodNotea Colour difference between sample before application and after a three-month in situ exposure, given in ΔE units in the Commission Internationale de l’Eclairage (CIE) 1976system.Phase A: preliminary selection of biocides For assessment of the first criterion, the conservation teamTen biocides effective against a vast spectrum of micro- carried out preliminary tests of the biocide solutions (made uporganisms and based on active ingredients of various chemical as recommended by the manufacturers) for their pH and theirgroups were selected for testing, based on the criteria below and effect on the colour and weight of sound Dionysus marble (whichon extensive bibliographic and market research, Table 1. All had is similar to Pentelic marble), Piraeus (Actitis) limestone andbeen safely used on various stone types before and according to sealing mortar specimens. Colour change of treated specimensthe manufacturers each biocide was only moderately to slightly was measured with a Sheen Micromatch Plus colorimeter usinghazardous, would not cause aesthetic, chemical or mechani- the CIE L*a*b* colour space after a 3-month in situ exposure.cal alteration to the stone and was compatible with inorganic Dry weight change (%) was measured after immersing thematerials. specimens in the biocide solutions overnight. In both cases, The compatibility of the biocides with stone and conservation acceptable changes were considered to be those similar to thosematerials and their efficacy against micro-organisms would be produced by deionized water [6]. Biocidal efficacy againsttested in vitro and in situ. micro-organisms was examined by the environmental micro- biologists using molecular techniques [5]. LD50 oral (rat) dataPhase B: laboratory and in situ assessment of biocides on sound indicated the toxicity class of the product and its safety for thespecimens user and the environment when used in situ. Ease of applicationThe criteria set for the biocides to be used on the Acropolis was evaluated by taking into account a product’s state (solidmonuments were: or liquid), the solvent type needed (water or other) and any pre- • no undesirable mechanical, chemical or aesthetic altera- caution measures required. tions to the stone substrates or the inorganic conservation The outcome of this work led to the selection of D/2 materials used; Architectural Biocide, Preventol R80 (quaternary ammonium compounds) and Algophase (organochlorinated compound) that • efficacy against the microbial consortium for two to four matched the stated criteria relatively well, Table 2. years; • safety for the environment and user (World Health Phase C: in situ evaluation of biocides on ancient biodeterio- Organisation (WHO) toxicity class of 2–3); and rated marble surfaces In situ environmental conditions include numerous param- • ease of preparation and in situ application. eters that cannot be accurately simulated in the laboratory. 76
  4. 4. Fig. 5 Marble surface treated with Algophase, D/2 Architectural Biocide Fig. 6 Marble exfoliations being cleaned using hydrogen peroxide. and Preventol R80, 21 months after treatment. After 26 months Photo: S. Papida. all surfaces were still satisfactorily clean and no recolonization was macroscopically noted. Photo: S. Papida. joining of fragments, filling of discontinuities and sealing. Little related information was found in the literature. The microbiol-The microbiologists were concerned that biocides usually ogists suggested that biocide application should follow conserva-have a different elimination effect on a mixed in situ micro­ tion procedures and that biocides should not be removed afterpopulation compared with an in vitro isolated micropopulation. application. In contrast, the manufacturers’ guidelines regard-Conservators were concerned about the possibility of undesired ing both issues were variable. An additional concern was thatside effects on biodeteriorated ancient stones after the use of biocides may gradually be converted to nutrients and enhancebiocides. recolonization [8]. The in situ efficacy of the three biocides when applied on The conservators therefore conducted further testing on bio-biodeteriorated marble surfaces bearing a dark chasmoendolithic deteriorated stone and sealing mortar surfaces with the aim ofpresence amongst dense exfoliations was measured relative to macroscopically monitoring the microbial removal potential andtime and conservation effects: the recolonization time for each product as well as assessing its applicability. Some trials were supported by in vitro microbio- • effect over time logical examinations. All biocides were applied to chasmoendolithically bio- The descriptions below focus on the rationale rather than the deteriorated marble surfaces during the dry season and results of the processes since biocide efficacy and recolonization caused a staining effect during the first 24–72 hours that time will always depend on the substrate, environmental param- gradually disappeared; a reduction in the microbial pres- eters, deterioration mechanisms and conservation materials and ence was observed on the surfaces after the rains started. methods involved. After 26 months all surfaces are satisfactorily clean and The YSMA systematic conservation protocol for treatment of no recolonization has been noted macroscopically, Fig. the marble includes the following steps: 5. In vitro monitoring by the microbiologists is still in progress but, as expected, recolonization time is directly 1. surface consolidation with repeated limewater suspen- related to the toxicity of the products [7]. sion sprays; • conservation effect 2. mapping and safe removal of loose exfoliations and The surface consolidation and cleaning processes that fragments; take place during systematic conservation were thought 3. cleaning of the interior surfaces, exfoliations and dis- to prolong recolonization time so the three biocides were continuities using deionized water, hydrogen peroxide applied to both treated and untreated chasmoendolithi- solutions and tools; cally biodeteriorated marble surfaces. Surface consoli- dation, the first conservation stage for stones suffering 4. joining of fragments using Portland cement; from intergranular disaggregation and exfoliation, took 5. filling of surface discontinuities by injecting inorganic place via 40 successive limewater suspension sprays. The grouts; and surface was cleaned using hydrogen peroxide solutions, deionized water and tools, Fig. 6. 6. sealing of joined fragments and filled surface disconti- nuities with inorganic mortars, based on white Portland As with the previous test applications, the conservators cement, calcium hydroxide, pozzolans, silicate sand and noted no aesthetic alteration to the surfaces and there inorganic pigments. was a satisfactory removal of the microbial presence after the rain. The ongoing in vitro research, however, • the effect of consolidation and cleaning suggests that conservation treatment does not prolong Consolidation via limewater suspension sprays is the the recolonization time [7]. first step towards the conservation of stone surfaces suf- fering from intergranular disaggregation or exfoliation.Phase D: developing an application methodology In an attempt to detect the best stage for biocide applica-As well as selecting suitable biocides, the conservators, advised tion, biocides were applied on treated (consolidated andby microbiologists, also aimed to develop an application meth- cleaned) and untreated biodeteriorated marble surfacesodology compatible with the in situ materials, methods and (with exfoliations and a black and green chasmoendo-working conditions. A principal question was whether biocide lithic presence) with the aim of measuring the effectsapplication should be before or after consolidation, cleaning, of the treatments on the biocide’s efficacy. Macroscopic 77
  5. 5. the rain — was indispensable for improving the aesthetic result. Moreover, failure to remove these organic remains provides micro-organisms with a nutrient substrate. • sealing mortars Inorganic sealing mortars are also affected by micro- organisms. Removal and replacement of affected mortars is possible, but may be constrained by lack of time and personnel and by the risk of material loss when joined fragments, exfoliations or intergranular disaggregation are involved. Minimum intervention is preferred and the prolongation of the mortars’ service life is sought. Effective biocidal elimination of organic remains on mortars was macroscopically observed after rainfall. Partial removal of both recently applied and older biode-Fig. 7 Cleaning before biocide application resulted in effective removal teriorated mortars showed that their decay and cohesion of epilithic mats (second and third columns of squares). Photo: loss was rather superficial, so biocide application could S. Papida. probably prolong their lives. Biocides can be used before and after new mortar applications to better safeguard the interventions. DISCUSSION Biodeterioration of stone monuments is a complicated problem that needs an interdisciplinary approach by experienced con- servators and specialized biologists. Its control strategy should involve careful in vitro and in situ examination of the stone substrates, (micro)flora and fauna and biocides. On the Acropolis monuments, manual plant elimination was suggested to avoid the danger of herbicides, but for control of extensive microbial decay the decision was taken to use biocides. Test applications were undertaken to develop the best meth- odology for various substrates, depending on their properties, condition, micro-environment, compatibility with conservation materials, application methods and in situ constraints. It is pos-Fig. 8 Rain resulted in effective removal of chasmoendolithotrophs on sible to draw a few conclusions from these tests regarding the biodeteriorated marble surfaces that were treated with a biocide use and application of biocides: (right fragment). Photo: S. Papida. • applying biocides after consolidation seemed to prevent their in vitro efficiency [7]. It is worth further investi- observations showed a remarkable removal of the gation into why limewater consolidation prevents the microbial presence when the biocide was applied after interaction of micro-organisms with the biocides. consolidation and cleaning. Moreover, biocide applica- tion on unconsolidated surfaces inevitably causes greater • cleaning before biocidal application seemed to facilitate material loss. However, raw microbiological data up to removal of organic remains resulting in aesthetically now suggest that the action of biocides, applied after the better surfaces. The prolongation of recolonization time treatments, was limited since recolonization time was is anticipated. shorter [7] • biocidal treatment of both older and newly applied mor- • the effect of cleaning alone tars prolongs their service life as well as the integrity of Knowing whether biocides facilitate cleaning or if joined fragments and loose exfoliations. cleaning prolongs biocide efficacy would indicate to con- • repeated applications are suggested depending on the servators whether biocides should be applied before or recolonization time, the condition of the substrate, the after cleaning. Biocides were applied on marble bearing toxicity of the product and the substrate’s accessibility. epilithic coloured mats or chasmoendolithic microbial presence and on darkened sealing mortars, both cleaned Biocides are definitely not a panacea for biodeterioration for a and uncleaned. Macroscopic observations showed that: number of reasons. Micro-organisms soon become unaffected by the biocides’ active ingredients and more toxic products are – cleaning before biocide application facilitated removal required, leading to safety hazards for the user, environment of organic remains, especially the epilithic mats, and had and monument during their in situ preparation, use and proper aesthetically better results, Fig. 7. Surfaces are being disposal [8]. Accessibility is another significant factor for large- monitored macroscopically for recolonization but clean- scale monuments such as the Acropolis. Biologists suggest ing before biocide application is expected to retard it. that biocides are applied to the largest possible area in order – biocide applications on untreated marble surfaces to prevent contamination. However, working conditions on the resulted in an acceptable removal of the chasmoendo- monuments mean that biocides can be applied only where res- lithic microbial presence that was more apparent at a toration and systematic conservation are currently taking place macroscopic scale after rainfall, Fig. 8. In all cases it was and scaffolding permits access. On fully accessible building understood that removal of the biocide along with the stones, where conservation methods and materials can be moni- dead cells some days later — either mechanically or by tored over a long period, less toxic products (e.g. Architectural 78
  6. 6. D/2) can be tested and re-applied or abandoned. The opposite is   2 Krumbein, W.E., Pantazidou, A. and Urzì, C., Report of the Firsttrue for architectural members conserved and replaced high on Phase of the Acropolis Project. Part II: Detailed Description of Samples, Microbial Communities and Photographic Documen-a monument: access is impossible after the end of restoration tation, report to Acropolis Restoration Service (YSMA) (1991)projects and the removal of scaffolding, so biocides with a longer (unpublished).recolonization time (e.g. Preventol R80 or Algophase) may be   3 Diakumaku, E., Gorbushina, A.A., Krumbein, W.E., Panina, L.necessary. In all cases, safety precautions must be taken by the and Soukharjevski, S., ‘Black fungi in marble and limestones — anuser and the minimum amount necessary should be carefully aesthetical, chemical and physical problem for the conservation ofprepared and applied during the dry season in order to prevent monuments’, Science of the Total Environment 167 (1995) 295–304.release of toxic materials into the environment.   4 Stotzky, G. and Burns, R.G., ‘The soil environment: clay-humus- In practice, biocide re-application is also affected by the microbe interactions’, in Experimental Microbial Ecology, ed. R.G.general conservation principle of minimum intervention since Burns and J.H. Slater, Blackwell Scientific, Oxford (1982) 105–133.every conservation treatment has the potential to cause damage.   5 Karagouni-Kyrtsou, A., Study of the Microbial Flora of the Acropo-Conservators may have to supplement the microbiologists’ data lis Monuments, report to Acropolis Restoration Service (YSMA) (2005) (unpublished) [in Greek].for recolonization with their own macroscopic observations andre-apply a biocide only when the process seems less harmful than   6 Papida, S., Garbis, D. and Papakonstantinou, E., Report Regardingthe biodeterioration type encountered. the Conclusions Derived from the Study of the Microbial Flora of the Acropolis Monuments and the Work for the Biocides Selection Last but not least, plant and animal elimination is an indispen- and Control, report to Acropolis Restoration Service (YSMA)sable part of an integrated biodeterioration strategy. The seasonal (2006) (unpublished) [in Greek].manual elimination of plants and the exclusion of pigeons need   7 Katsifas, S., Botany Department, Faculty of Biology, University ofto become a priority for the management of a site. Some plant Athens, personal communication, 14 September 2009.elimination efforts have recently been initiated at the Acropolis   8 Warscheid, T. and Braams, J., ‘Biodeterioration of stone: a review’,monuments with the co-operation of specialized mountaineers International Biodeterioration and Biodegradation 46 (2000)but progress is still needed until it becomes a regular part of the 343–368.annual schedule. AUTHORSCONCLUSIONS Sophia Papida trained as a conservator of antiquities and works of art at the Technological Institute of Athens. She has an MA in museumThe co-operation of conservators and biologists towards a studies (University of Leicester, UK) and has conducted postgraduatebiodeterioration control strategy produced useful information research on stone biodeterioration (University of Portsmouth, UK). Shefor the preservation of the Acropolis monuments. Given their has worked at various archaeological sites in Greece and since 2000 hassupreme cultural importance, this project has been the focus of been employed as a stone conservator at the Propylaea by the Acropolis Restoration Service (YSMA). She is interested in stone biodeteriorationmuch attention. and the interpretation of conservation for the wider public. Address: The Results include the identification of plants and micro- Acropolis Restoration Service (YSMA), 10 Polygnotou, 10555, Athens.organisms that adversely affect the monuments. Constraints Greece. Email: spapida@gmail.comthat inevitably affect choices and treatment potential have also Dionysis Garbis trained as a conservator of antiquities and works of artbeen identified and include the varying condition of the stone, at the Technological Institute of Athens. He has worked at the Verginaco-existing and synergistic deterioration mechanisms, the scale excavations and taught conservation in state institutions of professionalof the monuments and their exposure to the natural environment. training. Since 2000 he has been employed as a stone conservator at theEvidence from both laboratory and in situ tests, combined with Erechtheion by the Acropolis Restoration Service (YSMA). He is inter- ested in stone biodeterioration, laser cleaning and management of ar-environmental and working conditions on the one hand and with chaeological sites. Address: as for Papida. Email: ct06170@ct.aegean.grconservation theory and practice on the other, are some of theparameters that raise complications and combine to affect the Evi Papakonstantinou holds a diploma in chemical engineering from the National Technical University of Athens and has been head of thechoice of suitable application methods. surface conservation project at the Acropolis monuments since 1987. In this work, no ‘wonder’ materials or methods have been Her research interests include stone deterioration mechanisms as well asproposed. Instead it is argued that a strategy based on practical stone conservation materials (consolidants, inorganic mortars, etc.) andtesting, ceaseless monitoring and preventive care should take methods (consolidation, cleaning, protection). Address: as for Papida. Email: epapak@yahoo.complace in order to develop a suitable methodology for each typeof substrate, biodeterioration pattern or working environment. Amalia D. Karagouni, professor of microbiology at the Biology Depart-Systematic biodeterioration control processes are still being ment, National and Kapodistrian University of Athens, holds a biology degree and a PhD from the University of Warwick (UK) and works indeveloped within our routine care programme but we are keen the fields of genetics, applied microbiology, microbial ecology and bio-to share our experiences and results to date with other conser- technology. Her research activities include isolation of micro-organismsvators in order to promote the best possible preservation of our from particular ecosystems in Greece, their identification throughmonuments. phenotypic and genotypic characteristics, isolation and analysis of total DNA, identification of genes from environmental samples and analysisACKNOWLEDGEMENTS of environmental food samples for the identification of genetically modi-The authors are grateful to the Committee for the Restoration of the fied DNA. She participates in numerous funded research programs, hasAcropolis Monuments for their support. C. Vasiliadis (conservator, organized several international conferences and is a member of manyFirst EPCA) and Dr E. Katsifas (environmental microbiologist, NKUA) international scientific associations. Address: Department of Botany,are acknowledged for their co-operation; S. Cather and the preprint Microbiology Group, National Kapodistrian University of Athens,editors for their useful suggestions; and finally all biocide companies Faculty of Biology, 157 81, Athens, Greece. Email: akar@biol.uoa.grfor kindly providing product samples. The project was co-financed bynational and EU funds.REFERENCES  1 Vallianatou, E., Protection of the Athens Acropolis Monuments Structures From Plants, report to Acropolis Restoration Service (YSMA) (2007) (unpublished) [in Greek]. 79