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Earth’s Atmosphere’s Self-Purification Mechanism Unveiled by Scientists

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Human activities release many types of pollutants into the air, and without a molecule called hydroxide (OH), many of these pollutants would continue to accumulate in the atmosphere.

A recent study published in the Proceedings of the National Academy of Sciences shows that a unique combination of atmospheric conditions can generate hydroxide (OH) molecules that help clean the atmosphere by neutralizing pollutants even in the absence of sunlight.

The scientific team, which included Sergey Neskorodov, professor of chemistry at the University of California, Irvine (UCI), reported that the strong electric field present at the interface between water droplets in the air and the surrounding air can produce hydroxide through a previously unknown mechanism.

The discovery changes scientists’ understanding of how to clean the air of things like anthropogenic pollutants and greenhouse gases that hydroxide (OH) can react with and be removed.

“We need hydroxide to oxidize hydrocarbons, otherwise they will endlessly accumulate in the atmosphere,” said Nizhegorodov.

“Hydroxide plays a key role in the history of atmospheric chemistry, driving reactions that break down airborne pollutants and help remove harmful chemicals such as sulfur dioxide and nitric oxide,” explained Christian Georges, an atmospheric chemist at the University of Lyon in France and lead author new research. “which are toxic gases from the atmosphere. A complete understanding of sources and sinks of hydroxide (OH) is an important factor influencing atmospheric chemistry to understand and mitigate the effects of air pollution.”

Previously, researchers assumed that sunlight was the main factor in the formation of hydroxide.

Nizhegorodov noted that it is widely believed that the hydroxide is formed using photochemistry or redox chemistry, which requires sunlight or mineral catalysts to operate. However, the current study casts doubt on this assumption and says that in the purest water, hydroxide can spontaneously form due to special conditions on the surface of the droplets.

The team built on previous studies by Stanford University scientists led by Richard Zary that reported the spontaneous formation of hydrogen peroxide on the surface of water droplets.

The new data helps explain the unexpected results of Zari’s group.

The team measured the concentration of hydroxide in different flasks, some containing water and air on the surface, while others contained only water without air, and monitored the production of hydroxide in the dark by inserting a “probe” molecule into the flasks that glows when it interacts with the surface. hydroxide.

They saw that the rate of hydroxide production in the dark mirrored and even exceeded the rate of stimuli such as exposure to sunlight.

“Enough hydroxide will be created to compete with other known sources of hydroxide,” said Nizhegorodov. “At night, when there is no photochemistry, hydrogen is still produced at a faster rate than otherwise.”

Neskorodov said the results change understanding of hydroxide sources, which will change how other scientists build computer models that try to predict how air pollution will occur.

“This could drastically change air pollution patterns. Hydroxide is an important oxidizing agent inside water droplets, and the main assumption in the models is that the hydroxide comes from the air, rather than being formed directly in the droplet,” Nizhegorodov explained.

Nizhegorodov believes that the next step to determine whether the new mechanism of hydroxide formation plays a role is to conduct carefully designed experiments in real atmospheres in different parts of the world.

Source: phys.org.

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