Scientists say buildings aggravate air pollution by releasing nitrogen gases into the urban air.
A new study on the matter of urban air pollution was presented at the American Chemical Society meeting in Boston.
According to this study, the sunlight has an effect on the grime found on city buildings and other surfaces in urban outdoor areas. The grime releases nitrogen oxide compounds into the air, aggravating urban pollution.
Dr. James Donaldson, researcher at the University of Toronto, believes that what comes out of this recycling process is a combination of two gases: nitrous acid and nitrogen dioxide. Nitrogen dioxide (NO2) is toxic, while nitrous acid (HNO2) promotes photochemical smog in urban areas.
The results of the study made researchers understand that nitrates do not become inactive in the urban grime formed on buildings and other urban surfaces, as a result of the high levels of pollution caused by factories and cars.
Up until now, nitrogen oxide and other compounds were not seen as a reason for pollution in urban areas, but this study has proven that recycling of compounds might play an important part and actually aggravate pollution.
Researchers couldn’t determine to what extent this is happening, but it is considered to be a significant contributor to pollution, according to Dr. James Donaldson.
Donaldson and his fellow researchers believe that there is a significant amount of recycled nitrogen oxide in the atmosphere that could generate a great amount of ozone.
Previous research has also indicated that grime releases more nitrates when exposed to a solar simulator. This did not happen when the grime was in the dark. Scientists have concluded that sunlight, be it artificial or natural, can make the nitrogen compounds active, by chemically converting them. This makes the compounds go back into the atmosphere.
Specialists from Germany have also studied the same phenomenon. Their study suggested that grime from shaded areas contained 10% more nitrates than the grime that has been exposed to natural sunlight. They came to the same conclusion: nitrates were being released back into the air when the grime was exposed to sunlight.
There will be even more studies on this matter, as the researchers hope to understand more about the recycling of compounds, taking into account the effects of other factors such as the humidity, the amount of illumination and the grime levels needed for the recycling process to take place.
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