A new study that looked into South Coast Air Basin in California reveals that asphalt roads and roof coverings can put out secondary organic aerosol (SOA) when exposed to hot sunshine.
The research implies that although cars still produce more air pollution, SOAs emitted by the asphalt road also contribute a significant amount of pollutants that go unrecorded.
Secondary Organic Aerosol (SOA)
Secondary organic aerosols are not always mentioned when the subject of air pollution comes up because it mostly talks about the pollutants caused by motor vehicles or factories. SOA from hot asphalt often goes unreported as a contributor to urban air pollution.
But if ever emissions from motor vehicles continue to go down, it is now more important to discuss about SOAs. Governments should have plans to track down and remove these secondary pollutants that have a significant adverse effect on public health and the environment, although lesser than car pollutants.
Chemical and environmental engineer, Peeyush Khare from Yale University, said that the main finding of their research reveals that asphalt-related air pollutants emit a substantial and diverse mixture of organic air pollutants activated by the hot weather or environmental conditions.
In their experiment, the researchers heated up the asphalt in temperatures that range from 104 to 392 degrees Fahrenheit (40 to 200 degrees Celsius) monitored inside a tube furnace. That method allows them to determine the levels of SOA in hot temperatures like California is experiencing.
They found that SOA emissions doubled as temperatures rose to 140 degrees Fahrenheit and continued to rise as the temperature increases. In the end, they recorded a 70% increase per 68 degrees Fahrenheit from 140 degrees Fahrenheit to 284 degrees Fahrenheit.
Furthermore, the asphalt emissions stuck around, especially under the influence of sunlight, even if asphalt emissions slowed over a week. That means solar radiation causes an increase of up to 300% in road asphalt emissions.
This finding is not good news for a climate that is continuously getting hotter each year.
Drew Gentner, a chemical and environmental engineer, said that when they calculated the expected rate of steady emissions, it showed that the time for compounds to diffuse through the highly viscous asphalt mixture determines that rate of continued emissions.
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Asphalt-Related Emissions Not To Be Ignored
The study, published in Science Advances, suggests more tests to be done to exactly understand the asphalt-related emissions and chemical processes that contribute to air pollution. More research is needed to know how these emissions will change over time as roof coverings and asphalt are worn down.
With paved roads and roofs in the cities in the United States, this issue should not be ignored, especially in places such as California that usually experience good weather and sunshine.
Recently, another study revealed that the binder mix that holds asphalt together can react with sun and rain that releases a toxic and carcinogenic polycyclic aromatic hydrocarbons, another kind of pollution in which scientists are still investigating.
Read More: Air Pollution, Smoking, and a Person's Built Environment May Lead to Childhood Obesity, Study
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