Sunny days were all fun and games until this study came along and proved that they could be exceptionally bad for our health. Apparently, the urban grime that creeps on buildings reacts when sunlight hits, causing air pollution.
A phenomenon never studied before, the release of nitrogen oxide compounds that reside in the building-coating grime is something that Dr. James Donaldson of Toronto University in Canada has been concerned about. The research shows that sunlight is a natural trigger for the soot covering statues and other urban outdoor surfaces to be released in the air we breathe.
More than that, this study reverts the long-standing concept that the nitrates contained in urban grime are static, locked in place. As it goes, the current understanding of air pollution excludes the fact that nitrogen oxides can be recycled and transferred from building surfaces.
After analyzing the situation in a real-world environment through field studies, researchers concluded that this phenomenon is very much happening. Its extent is yet unknown, but further investigation might conclude it is quite a significant factor to urban air pollution.
According to Dr. Donaldson, urban grime can be defined as a compound of thousands of chemical elements that are scattered in the air by factories, traffic and other sources. The most dangerous are nitrogen oxides, because they have the ability to combine with other air pollutants, resulting in ozone, the chief cause of smog.
The long-standing theory regarding nitrogen oxides trapped in grime is that once they settle on a surface, they become inactive. Data collected by Dr. Donaldson’s team, however, proves that notion wrong.
Lab work showed that nitrate disappeared from grime at a rate that couldn’t be simply explained by wash-off due to rainfall. When exposed to artificial sunlight, the disappearance rate of nitrate was 10,000 times higher the rate of a water-based solution.
In further experiments, researchers observed how grime reacted when exposed to artificial sunlight versus keeping it in the dark. Results showed that more nitrates escaped from the exposed grime, suggesting that light has the chemical ability of reactivating nitrogen compounds, which then return in the air.
Lab conclusions were tested in Leipzig, Germany, and Toronto, proving that we still have a lot to understand about urban air pollution. Dr. Donaldson is scheduled to present the team’s findings at the 250th National Meeting and Exposition of the American Chemical Society.
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