So far, much of the focus of this blog has been on the relationship between air pollution and various aspects of human functions or activities. Have you ever wondered if the air around us is toxic not only to us, but also to the buildings we live, work and play in, as well as the infrastructure we use? Read on to find out!
Building degradation has been found to be primarily attributed to air pollution. Atmospheric pollutants in both wet and dry forms undermine materials through abrasion, deposition and removal, direct and indirect chemical attack, as well as corrosion (Rao et al., 2016). Air pollution leaves varying levels of damage on building integrity, depending on its material composition. These findings tie in well with real world observations of the deteriorating Taj Mahal and Charminar, ancient monuments made of limestone believed to be highly vulnerable to acid corrosion.
Figure 1. Table showing the levels of effect of air pollution on different materials (Rao et al., 2016)
Figure 2. The Taj Mahal turning yellow due to air pollution (Rao et al., 2016)
Figure 3. Air cracks on Charminar due to air pollution (The New Indian Express, 2019)
The adverse effects of air pollution on building material quality are corroborated by Ivaskova et al.’s (2015) spatial analysis based in Slovakia. By comparing spatial differences in SO2 deposition, the authors managed to illustrate a strong positive trend between SO2 concentration and the level of mass loss or surface recession for carbon steel (unalloyed steel), sandstone, and limestone, all of which are deemed to have “high” sensitivities to air pollution (Rao et al., 2016).
According to Roberts (2005), surface recession rate may be understood as the “difference in thickness between the relatively unweathered base and the weathered top of the [material]”. The high sensitivity of building materials to SO2 stems from the fact that sulfuric acid reacts with lime compounds to form calcium sulfate that is deposited on material surfaces, leading to both destructive volume expansion (surface recession) and disintegration (mass loss) (Demirbas et al., 2001)
Figure 4. Map of average SO2 deposition in different localities of Slovak Republic from 2004 to 2012 (Ivaskova et al., 2015)
Figure 5. Map of annual average mass loss of carbon steel (unalloyed steel) after one year of exposure to SO2 (Ivaskova et al., 2015)
Figure 6. Map of annual average surface recession of limestone after one year of exposure to SO2 (Ivaskova et al., 2015)
Figure 7. Map of annual average surface recession of sandstone after one year of exposure to SO2 (Ivaskova et al., 2015)
Notwithstanding the above, Kumar and Imam (2013) suggest that the impact of SO2 itself should gradually decline in the coming decades given global commitments to curb the emission of pollutants. They shed light on an interesting perspective that is geared towards how climate change induced by air pollution will exert greater impact on building and infrastructure integrity in the years to come.
Of particular interest to me was their model (Figure 8) of the projected carbon steel thickness loss given various environmental/climatic scenarios. The base case Scenario 1 assumes that SO2 and PM10 concentrations will decrease, precipitation will increase slightly, and global temperatures will rise over the next few decades leading to 2090. Scenario 2 assumes that neither of these parameters will change, Scenario 3 assumes that only warming takes place, while Scenario 4 assumes a larger increase in precipitation. As observed, Scenario 4 represents a huge spike in thickness loss as compared to the base case. This implies that the effects of climate change will far outweigh those of air pollution on its own. While the exact relationship between precipitation and carbon steel deterioration was not made known, I am compelled to believe that higher precipitation will enhance the production of acids through mixing with atmospheric pollutants that have long residence times.
Figure 9. Graph showing the projected varying effects of different environmental/climatic scenarios on thickness loss of carbon steel (Kumar and Imam, 2013)
Although no building collapses have been directly linked to air pollution, it appears that air pollution does indeed have dire consequences on building and infrastructure integrity. That, combined with poor workmanship or design, could very well translate to disastrous loss of property and lives in the worst case scenario. Given the pressures of impending climate change, will reducing air pollution be sufficient? I guess only time will tell.
Until the next entry, breathe safe and be safe!
References
Demirbaş, A., Öztürk, T., & Karataş, F. Ö. (2001). Long-term wear on outside walls of buildings by sulfur dioxide corrosion. Cement and Concrete Research, 31(1), 3–6. https://doi.org/10.1016/s0008-8846(00)00447-6
Ivaskova, M., Kotes, P., & Brodnan, M. (2015). Air pollution as an important factor in construction materials deterioration in Slovak Republic. Procedia Engineering, 108, 131–138. https://doi.org/10.1016/j.proeng.2015.06.128
Kumar, P., & Imam, B. (2013). Footprints of air pollution and changing environment on the sustainability of built infrastructure. Science of The Total Environment, 444, 85–101. https://doi.org/10.1016/j.scitotenv.2012.11.056
The New Indian Express. (2019). Insects and rain: Charminar fights a losing battle with natural elements. The New Indian Express. Retrieved March 4, 2023, from https://www.newindianexpress.com/cities/hyderabad/2019/jul/10/insects-and-rain-charminar-fights-a-losing-battle-with-natural-elements-2001925.html
Rao, N. V., Rajasekhar, M., & Rao, G. C. (2016). Detrimental effect of Air pollution, Corrosion on Building Materials and Historical Structures. American Journal of Engineering Research, 3(3), 359–364. Retrieved March 4, 2023, from https://www.researchgate.net/publication/286347487_Detrimental_effect_of_Air_pollution_Corrosion_on_Building_Materials_and_Historical_Structures.
Roberts, S. M. (2005). Surface-recession weathering of marble tombstones: New field data and constraints. In Stone decay in the architectural environment (Vol. 390). essay, Geological Society of America. Retrieved March 4, 2023, from https://pubs.geoscienceworld.org/gsa/books/book/538/chapter-abstract/3801719/Surface-recession-weathering-of-marble-tombstones.