For their study, the researchers utilized two specific techniques to measure the amount of sulfur dioxide adsorbed by different cement and cement-based building materials. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) is an infrared sampling technique that can verify the chemical and physical structure of solid, liquid, and gaseous materials; on the other hand, X-ray absorption near edge structure (XANES) is a kind of X-ray Absorption Spectroscopy that can provide information on the oxidation state, coordination environment, and bonding characteristics of particular elements.
Using these techniques, they found that sulfur dioxide clung to the porous surfaces of the aggregates, and even oxidated into sulfite and less-dangerous sulfates species after reacting with specific concrete constituents, like calcium hydroxide.
As one of the most common air pollutants in the world, sulfur dioxide emissions come from a variety of sources. The biggest sources of these harmful gases are power plants and other industrial facilities; other sources of sulfur dioxide include ships, vehicles, and heavy equipment that make use of fuel with high amounts of sulfur. Cement kilns themselves are one of the most prominent industrial sources of sulfur dioxide, and produce at least 20 percent of emissions. (Related: UK warned to clean up its air as deadly pollution continues to increase)
Moreover, the environmental impact of concrete has been extensively researched about and documented. Simply making concrete results in elevated outputs of carbon dioxide, and concrete production has been ranked as the third biggest producer of man-made carbon dioxide, right after transportation and energy generation. Approximately four to five percent of the worldwide total of carbon dioxide emissions can be attributed to concrete production.
The irony has been noted by Orlov, who commented: “Even though producing concrete causes air pollution, concrete buildings in urban areas can serve as a kind of sponge adsorbing sulfur dioxide to a high level. Our findings open up the possibility that waste concrete coming from building demolitions can be used to adsorb these pollutants.”
Indeed, Orlov has noted that concrete continues to be the most widely used, and inexpensive, building material in the world. As such, Orlov noted that “the strategy of using pollution-causing material and turning it into an environmental solution could lead to new thinking in urban design and waste management.”
Although the efficacy of concrete in adsorbing air pollutants greatly diminishes over the passage of time, this could easily be remedied by crushing the concrete to expose new surfaces. Doing so, according to Orlov, would restore the air pollutant-adsorbing capabilities of the concrete.
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Fast facts on sulfur dioxide
- Sulfur dioxide is an invisible, colorless gas with a sharp smell likened to that of burnt matches.
- Although there are natural sources of sulfur dioxide, such as volcanoes, the majority of sulfur dioxide in the air originated from human sources.
- Sulfur dioxide negatively impacts both humans and the environment. Short-term exposure to sulfur dioxide can make breathing difficult, making it especially dangerous to children, the elderly, and people who are suffering from asthma. High concentrations of sulfur dioxide can worsen asthma attacks and aggravate existing heart conditions.
- Sulfur dioxide, along with other sulfur oxides, contributes to acid rain formation.
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