Origin of Salts
- Salts in building substrate and subsoils
- Road salts - deicing salt
- Salts of microbiological origin
- Salts Resulting from Restoration Materials
The salts that cause damage to buildings, including wall paintings, and monuments made of stone, brick and other inorganic building materials, can originate from both natural sources or human activities. Natural sources are, for example, salts present in the ground on which the building stands. But they can also be present in the material itself, for example brick or some cements, depending on their manufacture; in stones near flood plains or from the natural stone weathering cycle. They can be brought in by sea spray and wind, for buildings in coastal areas and some microorganisms growing on building materials may generate some. Salts originating from human activities can be linked to emissions from burning fossil fuels, agricultural activities, automotive combustion engines and the use of deicing salts. Historic buildings may also have been used to store salt or gun powder, or even as stables Over the years, salts will accumulate within or near the surface of the building as water evaporates. Since what migrates within the stone are the ions of the various salts present when water enters the porous system, the accumulation of ions upon water evaporation may result in the formation of different combinations of them,i.e., different salts to the ones entered the material originally.
Every natural liquid water can be considered a more or less diluted salt solutions as confirmed by simple electrical conductivity measurements. When water enters porous building materials, such as stone, brick, mortar or plaster, salts will also enter their pore space. As water evaporates at the suface of these materials, salts will accumulate near that area and eventually, some salt efflorescence will result.
Some salts are introduced into the buildings or monuments by human activity. These may result from the use of consolidants and/or cleaning agents such as alkaline materials, such as water glass building materials; some Portland cement in mortars, as well as historical use of the buildings for storage of salt or gun powder, or as stables. Some damages previously attributed to air pollution are now known to be due to the use of these materials [Klemm.etal:1999]Author: Klemm, Werner; Siedel, Heiner
Publisher: Wiss. Mitt. Inst. Geol. TU Bergakademie Freiberg
Title: Schwefelisotopenanalyse von bauschÃ¤dlichen Sulfatsalzen an historischen Bauwerken
. Deicing salts should be added to the list of these materials, especially since they are still in use mostly for roads, bridges and tunnels, affecting these structures and the foundations of buildings near them. Other sources for damaging salts can be fertilizers and some detergents that are introduced through ground and surface water. Finally, cleaning interventions based on the use of alkaline materials followed by an acid rinse, can leave soluble salts behind. This cleaning approach is mostly used for brick masonry in some countries, although there are records of their application on stone facades.
Many building materials are contaminated with salt-forming ions, varying from low to high concentrations. These can include natural stone or man-made ones, such as brick, lime, cement and mortars. The soil substrate and subsoil consistency, as well as the ground- and surface water contribute to this contamination [Roesch.etal:1993]Author: Rösch, Heinrich; Schwarz, Hans-Jürgen
Journal: Studies in Conservation
Title: Damage to Frescoes caused by sulphate-bearing salts: Where does the salt come from?
. So do natural emissions by volcanoes ((H2S, HCl, HF, SO2 etc.) and sea- water aerosols (mostly NaCl but other salts as well), [Steiger.etal:1994b]Author: Steiger, Michael; Dannecker, Walter
Booktitle: The conservation of monuments in the Mediterranean Bassin: Stone and Monuments: Methodologies for the Analyses of Weathering and Conservation, , proceedings of the 3rd international symposium, Venice, 22-25 June 1994
Editor: Zezza, Fulvio and Ott, Heinrich and Fassina, Vasco
Title: Determination of wet and dry depostion of atmospheric pollutants on building stones by field exposure experiments
[Steiger.etal:1997]Author: Steiger, Michael; Behlen, Andreas; Neumann, Hans-Herrmann; Willers, U.; Wittenburg, Christian
Booktitle: 4th International Symposium on the Conservation of Monuments in the Mediterranean - Proceedings
Editor: Moropoulou, A. and Zezza, F. and Kollias, E. and Papachristodoulou, I.
Title: Sea Salt in Historic Buildings: Deposition, Transport and Accumulation
[Steiger.etal:2002]Author: Steiger, Michael; Behlen, Andreas; Wiese, Utz
Booktitle: Salze im historischen Mauerwerk
Editor: Institut für Steinkonservierung Mainz
Publisher: IFS, Mainz
Title: Immissionsbelastung durch salzbildende Stoffe und Wirkung auf mineralische Baustoffe
Key: IFS Bericht 14
[Becker.etal:2005]Author: Becker, Karl-Heinz; Brüggerhoff, Stefan; Steiger, Michael; Warscheid, Thomas
Booktitle: STEIN. Zerfall und Konservierung
Editor: Siegesmund, Siegfried and Auras, Michael and Snethlage, Rolf
Publisher: Edition Leipzig
Title: Luftschadstoffe und Natursteinschäden
, but anthropogenic activities are becoming the most important contributors to salt contamination.
Among these are the industrial and traffic emissions, which produce a great number of aggressive substances, such as sulfur dioxide (at the origin of sulfates) [Wittenburg.etal:1993]Author: Wittenburg, Christian; Mangels, Henning; Wolf, Falk; Steiger, Michael; Bothmann, Thomas; Dannecker, Walter
Booktitle: VDI-Berichte 1060 (Materialien in ihrer Umwelt)
Title: Ein Vergleich von Schwefeldioxid-Depositionsgeschwindigkeiten auf Naturwerksteine aus verschiedenen experimentellen Ansätzen (Comparison of sulfur dioxide deposition velocities on building stones from different experiments)
and nitrogen oxides (originating nitrates), are the most common ones. It is still not fully understood, how ozone (O3) and the large number of organic compounds released participate in the deteroration mechanism of building materials. Immissions mostly reach the objects through dry or wet deposition [Steiger.etal:1989]Author: Steiger, Michael; Schulz, Michael; Schwikowski, Margit; Naumann, K.; Dannecker, Walter
Journal: Journal of Aerosol Science
Note: In order to estimate the atmospheric input of pollutants into coastal waters the removal mechanisms of dry and wet deposition have to be considered. Generally the latter one is assumed to be the more efficient sink process. However, since little is known about true rainfall amount at the open North Sea, the contribution of a continous dry deposition flux may also be of relevance, especially in the vicinity of the coast. Both removal processes are closely related to the aerosol size distribution and are preferentially depleting the mass in the largest size ranges. Thus particle size is considered to be a very important parameter for the characterization of airborne particles. We therefore started to measure ambient elemental size distributions at the research platform NORDSEE, which is located about 120 km apart from the coastline in the German Bight.
Title: Variability of aerosol size distributions above the North Sea and its implication to dry deposition estimates
by rainwater or fog, but also through accumulation in the subsoil.
Nitrates and organic salts such as oxalates mostly are of microbiological origin. While nitrates are transported into the object by humidity, calcium oxalates are usually formed in situ by microorganisms, where they remain due to their low solubility.
|[Becker.etal:2005]||Becker, Karl-Heinz; Brüggerhoff, Stefan; Steiger, Michael; Warscheid, Thomas (2005): Luftschadstoffe und Natursteinschäden. In: Siegesmund, Siegfried; Auras, Michael; Snethlage, Rolf (eds.): STEIN. Zerfall und Konservierung, Edition Leipzig, 35-45, %url%, %doi%|
|[Klemm.etal:1999]||%editor% Klemm, Werner; Siedel, Heiner (1999): Schwefelisotopenanalyse von bauschÃ¤dlichen Sulfatsalzen an historischen Bauwerken, %edition%, Wiss. Mitt. Inst. Geol. TU Bergakademie Freiberg, %address%, %pages%, %url%, %doi%|
|[Roesch.etal:1993]||Rösch, Heinrich; Schwarz, Hans-Jürgen (1993): Damage to Frescoes caused by sulphate-bearing salts: Where does the salt come from?. Studies in Conservation, 38 (4), 224-230, Url, %doi%|
|[Steiger.etal:1989]||Steiger, Michael; Schulz, Michael; Schwikowski, Margit; Naumann, K.; Dannecker, Walter (1989): Variability of aerosol size distributions above the North Sea and its implication to dry deposition estimates. Journal of Aerosol Science, 20 (8), 1229-1232, %url%, %doi%|
|[Steiger.etal:1994b]||Steiger, Michael; Dannecker, Walter (1994): Determination of wet and dry depostion of atmospheric pollutants on building stones by field exposure experiments. In: Zezza, Fulvio; Ott, Heinrich; Fassina, Vasco (eds.): The conservation of monuments in the Mediterranean Bassin: Stone and Monuments: Methodologies for the Analyses of Weathering and Conservation, , proceedings of the 3rd international symposium, Venice, 22-25 June 1994, %publisher%, 171-178, %url%, %doi%|
|[Steiger.etal:1997]||Steiger, Michael; Behlen, Andreas; Neumann, Hans-Herrmann; Willers, U.; Wittenburg, Christian (1997): Sea Salt in Historic Buildings: Deposition, Transport and Accumulation. In: Moropoulou, A.; Zezza, F.; Kollias, E.; Papachristodoulou, I. (eds.): 4th International Symposium on the Conservation of Monuments in the Mediterranean - Proceedings, %publisher%, 325-335, %url%, %doi%|
|[Steiger.etal:2002]||Steiger, Michael; Behlen, Andreas; Wiese, Utz (2002): Immissionsbelastung durch salzbildende Stoffe und Wirkung auf mineralische Baustoffe. In: Institut für Steinkonservierung Mainz (eds.): Salze im historischen Mauerwerk, IFS, Mainz, 1-10, %url%, %doi%|
|[Wittenburg.etal:1993]||Wittenburg, Christian; Mangels, Henning; Wolf, Falk; Steiger, Michael; Bothmann, Thomas; Dannecker, Walter (1993): Ein Vergleich von Schwefeldioxid-Depositionsgeschwindigkeiten auf Naturwerksteine aus verschiedenen experimentellen Ansätzen (Comparison of sulfur dioxide deposition velocities on building stones from different experiments). In: %editor%: VDI-Berichte 1060 (Materialien in ihrer Umwelt), %publisher%, 383-392, %url%, %doi%|