Einstein Science Reporting for Kids
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The pollution that grows at night

The tower used for studying aerosol chemistry during the CALNEX-SJV experiment.
[Photo by Sally Pusede]

Nitrogen oxides—you can call them "Nox"—are one kind of pollution that comes from burning gasoline and other fuels. They're produced when we drive cars, when we heat our homes, and in many other ways. Scientists have shown that they are involved in chemical reactions in the Earth's atmosphere that are warming up our planet.

Nox is also involved in building another kind of air pollutant called organic aerosols, according to a study in the 7 September issue of Science. Organic aerosols are tiny particles in the air. They're really tiny—about 50 of them could line up across the width of one of your hairs. Even though they're small, they can also affect the Earth's climate when a lot of them build up in the air. Some people, like those with asthma, can get sick from breathing in air with too many aerosols.

Andrew Rollins, a chemist at the University of California, Berkeley, and his fellow scientists wanted to find out more about where organic aerosols come from. Using a tall tower, they collected samples of air from the skies around Bakersfield, California. Their experiments showed some interesting things.

First of all, they found out that Nox is important for the chemical reactions in the air that create organic aerosols—when there's more Nox, there's also more aerosols. They also found out that most of this chemistry happens at night. When people drive cars and burn fuel in other ways all day long, it creates a lot of Nox that goes to work at night. If we could find ways to burn less fuel or burn it in cleaner ways, the scientists say, we might have less aerosol pollution to deal with.