Abstract
Background, aim and scope
Salt efflorescences markedly contribute to the alteration and deterioration of building material, in this case the Villamayor Sandstone of the facades in the Old Town of Salamanca, Spain (United Nations Educational, Scientific and Cultural Organization world cultural heritage site). A better understanding of the mechanisms of salt formation and the involved elements would allow more precise measures in monument conservation. The magnesium which is required for the salt precipitation originates from selective processes of hydrolysis. The source of sulphate, however, is presently not as clear. Identifying the source of the sulphur was the main goal of this research. Isotope ratio measurement of δ34S and δ18O was used to clarify the origins of Mg sulphate salts.
Materials and methods
A total of 56 Mg sulphate samples were collected in two different seasons (July and November 2005) from monuments of the Old Town of Salamanca. These sampled salt efflorescences were analysed for δ34S and δ18O by mass spectrometry. A ‘dual-inlet’ type by VG Isotech was used for δ34S and continuous flow type Isoprime by GV Instruments for δ18O. Samples were measured in triplicates and standard material was analysed for quality control.
Results
δ34S values range between 3.6‰ and 15.4‰ with a median value of 10.2‰ for the July samples and of 10.1‰ for November samples. The results of the sulphur ratios hint towards a bimodal distribution (with modes at δ34S = 6‰ and 12‰) for winter samples, which is less obvious during summer. δ18O values range from 7.1‰ to 41.1‰. However, most values range from 7.1‰ to 20.8‰, whereas only few summer samples show outliers towards higher δ18O values. The median δ18O value for July samples is 15.5‰ and for November samples 14.6‰.
Discussion
The isotopic ratios of the analysed sulphate samples were compared with values of possible source materials. Sulphur sources in the case of Salamanca are barites from the Villamayor Sandstone itself, sea spray, sulphides from regional rocks, biogenic sulphur (soil, avian excreta), as well as sulphur from anthropogenic sources such as building materials (especially mortar) or traffic exhaust. Salamanca is a representative site for non-industrial cities with no heavy industry and thus, there are no significant SO2 emissions from industry.
Conclusions
Based on the measured isotopic ratios, it was ascertained that more than one sole sulphur source is present. However, based on additional information about the source material and possible transport ways, some sources could be excluded whereas others only played a minor role. Finally, there is strong indication that the main sulphur source is atmospheric pollution and the exhaust emissions from vehicles in particular, while mortar as building material also contributes to a minor extent. The δ18O values support this hypothesis. Moreover, the reported δ18O values are a strong indicator of the secondary nature of the Mg sulphates. Isotope ratio measurement and especially the combined use of δ34S and δ18O values have proven to be a good instrument in clarifying the origin of salt efflorescences on buildings.
Recommendations and perspectives
Further studies should investigate more closely the isotopic composition of atmospheric aerosols in Salamanca in order to get a more detailed knowledge about the main sulphur sources, as well as to quantify the relation between the isotopic values and the amount and mineralogical form of the salts.
Similar content being viewed by others
Notes
Webpage Junta de Castilla y León: http://www.jcyl.es/scsiau/Satellite/up/es/MedioAmbiente/Page/PlantillaN3/1131977457126/_/_/_?asm=jcyl.
References
Alonso-Gavilán G (1981) Estratigrafía y sedimentología del Paléogeno en el borde suroccidental de la Cuenca del Duero (Provincia de Salamanca). Dissertation (inedited), Universidad Salamanca
Alonso-Gavilán G (1983) Sedimentología de las Areniscas de Villamayor. Stud Geol Salmant XIX:7–20
Alonso-Gavilán G, Moro MC, Cembranos ML, Areas A (1997) Barita de neoformación en la Arenisca de Villamayor (Salamanca). Estudio preliminar. Geogaceta 22:15–17
Arribas Moreno A, Polo Díez V, Jiménez Fuentes E (1984) La ‘Enfermedad de la piedra’ en la arenisca de Villamayor. Diagnóstico, tratmiento y conservacion. In Estudio sobre las alteraciones y tratamiento de la piedra de Villamayor, Monografías 3. Caja de Ahorros y Monte de Piedad de Salamanca
Blanco J (1989) Dinámica del proceso de alteración ambiental de la ‘Piedra de Villamayor’. Geogaceta 6:32–35
Buzek F, Cerny J, Sramek J (1991) Sulphur isotope studies of atmospheric S and the corrosion of monuments in Prague, Czechoslovakia. In: Krouse HR, Grinenko VA (eds) Stable isotopes: natural and anthropogenic sulphur in the environment. SCOPE 43. Wiley, Chichester, pp 399–405
Caron F, Tessier A, Kramer JR, Schwarcz HP, Rees CE (1986) Sulphur and oxygen isotopes in sulfate in precipitation and lakewater, Quebec, Canada. Appl Geochem 1:601–606
Coleman ML, Moore MP (1978) Direct reduction of sulfates to sulfur dioxide for isotopic analysis. Anal Chem 50(11):1594–1595
Farquhar GD, Henry BK, Styles JM (1997) A rapid on-line technique for determination of oxygen isotope composition of nitrogen-containing organic matter and water. Rapid Commun Mass Spectrometr 11:1554–1560
Graham L, Gray C (2002) Pacific 2001: Cassiar Tunnel study—gaseous emissions measurements. Presentation at the Symposium on Atmospheric Aerosols and Pacific 2001 Field Study, 85th CSC Conference, Vancouver, Canada, June 1–5, 2002
Hoefs J (2004) Stable isotope geochemistry, 5th edn. Springer, Berlin
Holt DB, Kumar R (1984) Oxygen-18 study of high-temperature air oxidation of SO2. Atmos Environ 18:2089–2094
Holt DB, Kumar R, Cunningham PT (1982) Primary sulfates in atmospheric sulfates: estimation by oxygen isotope ratio measurements. Science 217:51–53
Koziet J (1997) Isotope ratio mass spectrometric method for the on-line determination of oxygen-18 in organic matter. J Mass Spectrometr 32:103–108
Krouse HR (1980) Sulphur isotopes in our environment. In: Fritz P, Fontes JC (eds) Handbook of environmental isotope geochemistry. Vol. 1, The terrestrial environment. A. Elsevier, Amsterdam, pp 435–471
Krouse HR, Grinenko VA (eds) (1992) Stable isotopes: natural and anthropogenic sulphur in the environment. SCOPE, 43. Wiley, New York, pp 373
Krouse HR, Stewart JWB, Grinenko VA (1991) Pedosphere and biosphere. In: Krouse HR, Grinenko VA (eds) Stable isotopes: natural and anthropogenic sulphur in the environment. SCOPE 43. Wiley, Chichester, pp 267–306
Newman L, Forrest J (1991) Sulfur isotope measurements relevant to power plant emissions in northeastern United States. In: Krouse HR, Grinenko VA (eds) Stable isotopes: natural and anthropogenic sulphur in the environment. SCOPE, 43. Wiley, New York, pp 331–333
Norman A-L, Belzer W, Barrie LA (2004) Insights into the biogenic contribution to aerosol total sulphate and precipitation in the Fraser Valley afforded by isotopes of sulphur and oxygen. J Geophys Research D 109:D05311
Norman A-L, Anlauf K, Hayden K, Thompson B, Brook JR, Li S-M, Bottenheim J (2006) Aerosol sulphate and its oxidation on the Pacific NW coast: S and O isotopes in PM2.5. Atmos Environ 40:2676–2689
Pye K, Schiavon N (1989) Cause of sulphate attack on concrete, render and stone indicated by sulphur isotope ratios. Nature 342:663–664
Recio C, Fallick AE, Ugidos JM (1991) Sulphur isotope systematics of granitoids and associated rocks from the Ávila–La Alberca area (western Sistema Central, Spain). Rev Soc Geol España 4(3–4):371–381
Schoenau JJ, Germida JJ (1992) Sulphur cycling in upland agricultural systems. In: Howarth RW, Stewart JWB, Ivanov MV (eds) Sulphur cycling on the continents—wetlands, terrestrial ecosystems, and associated water bodies. SCOPE 48. Wiley, Chichester, pp 261–277
Siedel H (2000) Effects of salts on wall paintings and rendering in the Augustusburg Castle (Saxony). In: Rammlmair D, Mederer J (eds) Proceedings 6th International Congress on Applied Mineralogy. Vol 2, Göttingen Juli 2000. Balkema, Rotterdam, pp 1035–1038
Siedel H, Klemm W (2000) Evaluation of the environmental influence on sulphate salt formation at monuments in Dresden (Germany) by sulphur isotope measurements. In: Fassina V (ed) Proceedings 9th International Congress on Deterioration and Conservation on Stone-Vol. 1. Venice, 19–24 June 2000. Elsevier, Amsterdam, pp 401–409
Schleicher N (2006) Source identification of sulphate salt formation from monuments in Salamanca, Spain—a stable isotope approach. Diploma thesis, Institut für Geologie und Paläontologie, Universität Stuttgart
Torfs KM, Van Grieken RE, Buzek F (1997) Use of stable isotope measurements to evaluate the origin of sulfur in gypsum layers on limestone buildings. Environ Sci Technol 31:2650–2655
Türcke T, Norra S, Stüben D, Berner Z, Leosson M (1999) Identifikation der kfz-bürtigen Schadstoffbelastung mit Hilfe der Verhältnisse der stabilen Isotope von Kohlenstoff und Schwefel. Umweltwiss Schadst Forsch 11(3):127–133
Wadleigh M, Schwarcz HP, Kramer JR (1996) Isotopic evidence for the origin of sulphate in coastal rain. Tellus B 48:44–59
Acknowledgements
The authors thank Meggie Sotelo Martínez, Félix García García and Juan Manuel Rodríguez Salvador (Bartolo) for their laboratory assistance and general support. The authors also gratefully thank Dr. Stefan Norra from the Institute of Mineralogy and Geochemistry, Universität Karlsruhe (TH), Germany, for his helpful comments on the manuscript.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Schleicher, N., Recio Hernández, C. Source identification of sulphate forming salts on sandstones from monuments in Salamanca, Spain—a stable isotope approach. Environ Sci Pollut Res 17, 770–778 (2010). https://doi.org/10.1007/s11356-009-0196-3
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11356-009-0196-3