Polluted rain and monuments

1. Polluted rainand monuments

2. The pH of rainwater usually has a value of 5.5, allowing the life of flora and fauna without damaging resistant rocks like marble.

3. Marble • Thanks to the chemical and mechanical resistance to weathering, since ancient times marble was used to decorate prestigious buildings with capitels, columns or even statues and monuments.

4. However, the industrialization of the nineteenth century led to the increase of gas in the atmosphere, above all components as: • Dioxide and sulfur trioxide (SO2 and SO3) • Nitrogendioxide (NO2) • Carbon dioxide (CO2)

5. these gases react with the h2o, giving the following acids • SO2 + H2O ---> H2SO3 (sulphorous acid) • SO3 + H2O ---> H2SO4(sulfuric acid) • 2NO2 + H2O ---> HNO2 + HNO3 (Nitrous Acid and Nitric Acid) • CO2 + H2O ---> H2CO3 (carbonic acid)

6. These reactions can lower the pH value up to 2, resulting in a serious damage especially to the marble changing it from calcium carbonate (CaCO3) in gypsum (Calcium sulfate: CaSO4), more easily damaged by atmosphere agent.

7. The blackening and air pollution • Rainwater removes the gypsum that has been formed and so a new portion of the marble is exposed to the action of acid rain with a consequent progressive and continuous erosion of the building or of the artifact artistic.

8. Italy has the greatest concentration of historical and artistic heritage of the whole world • In the national territory, over 60,000 areas of cultural interest have been registered in the risk map (icr 1996).

9. In recent decades there has been a rapid degradation due to pollution as the major cause. • The decay of a work of art begins immediately after its completion and the speed depends on the materials and external agents.

10. The speed of action is increased by the presence of carbonaceous particles to which are attributed also the blackening on stone surfaces of monument or historic building.

11. Air pollution affects especially the degradation of the artistic heritage as determines the change of the gases and causes harmful chemical reactions. Limiting greenhouse effects meets the protection of art.

12. The index of biological contamination takes into account the level of biological events on monuments.

13. The organisms present on the works of art can be: • Natural , i.e. lichens, mosses • These are deposited on the surface of monuments • Frost • Salt Crystallisation • Microclimate • Thermal shock • Chemical • Anthropic ( caused by humans activities ) • Pollution • Acid rains

14. We can infer the degree of microorganism colonization by sampling the sediments and calculating the amount of ATP (adenine-tri-phosphate).

15. In 1995 the Ministry for Cultural and Environmental Heritage promoted the Risk Map of Italian Cultural Heritage. It still protects our territory and provides its members instruments for scientific and administrative support.

16. The risk map also allows us to calculate the risk of loss of all cultural heritage and to know their distribution on the Italian territory

17. The first ever comprehensive evaluation of the factors of degradation was made in Umbria which proved to be effective in the dramatic occasion of the earthquakes in Friuli.

18. THE MOST AGGRESSIVE SUBSTANCES FOR MONUMENTS CARBON DIOXIDE : it’s a natural component of the atmosphere. In theseyears the concentration of CO2hasincreasedbecause of the fossilfuelsadopted in the domesticheating and in industrial processes. Calcareousstoneartefacts and calcareous Sandstones are dissolved by slightly acidulate water.

19. SULPHURE COMPOUNDS (SOx) It’sprincipallypresent in the atmosphereassulphurdioxide (SO2), hydrogensulphide (H2S) and sulphates (SO4). In combustionprocessessulphureisoxidizedintosulphurdioxide(SO2). The presence of sulphureoxides in the atmosphereis the reason for the formation of gypsum. The latterconcernsstonematerial and bronze. Thisprocesscauses the loss of the superficiallayer of the material.

20. OXIDES OF NITROGEN(Nox): Theyare all the compoundsbetweennitrogen and oxygen in the differentoxidationstates. Generallynitrogenoxides are oxidized in the atmosphere by nitronicacid thatcorrodes the materialsurface.

21. ATMOSPHERIC PARTICULATE Theyare carbon particlesproduced by the combustion of fossilfuelswichsettle on stoneartefacts, bronzes, paintings and frescoesdamagingthem.

22. ATMOSPHERIC PARTICULATE Allthe kinds of particles can be found in the blackcruststhat cover monuments.

23. The particulatebecomes an integral part of the materialthatformsthem The substancesthat can deteriorate a work of art may be released from differentsourceslike: -COMBUSTION PROCESSES: likecarbon dioxide, sulphurdioxide and carbon particles; -MEANS OF TRANSPORT: thatproduces carbon nitrogen and sulphuroxides and particulate; -PROCESSING ARTEFACTS: that introduce in the atmospheresulphuricanhydride , hydrochloric acid , nitrogenoxides and particulate

24. GOOD CONSERVTATION PRACTICES • The synergy of both physical and chemical factors determines the degradation of a work of art, which causes subsequent restoration and cleaning. The resulting cultural loss is difficult to estimate in monetary terms, because of the intrinsic value of many artistic artefacts. Restoration and consolidation practices are often neither decisive nor definitive and must be repeated at regular intervals.

25. GOOD CONSERVTATION PRACTICES The key objectives to be achieved in the protection and conservation of works of art can be listed as follows: Slowing down of the degradation and consequent reduction in the loss of the original material Restitution and preservation of the aesthetic contents of the monument

26. It is estimated that, on average, the restoration of architectural surfaces costs from 500 to 750 € per square metre. This cost must be added with Charges for provisional deeds Design charges Security charges

27. Therefore, we can consider that the cost of the restoration reaches 1,000 - 1,500 € per square metre of surface. For example in Rome, as a rule, the restoration of surfaces, is performed at regular intervals of 25-30 years, corresponding to the Jubilees

28. The management system of geographic information allows us to represent on the risk map the relationship between territorial municipalities and distribution of cultural heritage.

29. Miningtown of Turin and superimposition of cultural belonging

30. Miningtown of naples and superimposition of cultural belonging

31. Scientific Experiment

32. Scientific Experiment • To prove the truth of transformation of marble to gypsum, we conducted an experiment in the school laboratory, by the reaction of hydrochloric acid and sulfuric acid on stones such as marble and travertine. Usually the sulfuric acids make these stones easy to damage but we did this experiment also with hydrochloric acid to accelerate this process.

33. Materials • To realize the experiment, we needed the following materials: - A piece of marble; - A piece of travertine; - Hydrochloric acid; - Dropper; - Sulfuric acid.

34. StepOne • Once positioned the piece of marble and travertine for the experiment, we dropped some sulfuric acid on marble and travertine. Marble Travertine

35. StepOne • As soon as let the acid, it reacted making bubbles. Marble Travertine

36. StepTwo • We repeated the experiment substituting sulfuric acid with hydrochloric acid to have a faster reaction although usually the surfaces are transformed by sulfuric acid. Travertine Marble

37. StepTwo • In fact, the reaction we obteined with the hydrocloric acid, was more visible and immediate then the other. Marble Travertine

38. Step Three • However, although hydrochloric acid had accelerating the process, before the final result we had to wait a day to see that the surface on which the solution had been applied, had become gypsum.

39. Conclusion • Thanks to this experiment we have seen how due to acid rain, in the long run (because of the low concentration of sulfuric acid) the marble becomes gypsum and then more subject to degradation.