10 Apr. (EUROPE PRESS) –
a strong electric field on the surface between the water droplets in the air and the surrounding air can create hydroxyl radicals (OH) by a previously unknown mechanism.
Human activities emit many types of pollutants into the air, and without hydroxyl (OH) radicals, many of these pollutants would continue to accumulate in the atmosphere.
How OH forms in the atmosphere was considered a whole story, but the finding by a team that includes Sergey Nizkorodov, a professor of chemistry at the University of California, Irvine, will change the way scientists understand how OH forms. Air is cleaned of things like man-made pollutants and greenhouse gases, which OH can react with and remove. “OH is needed to oxidize hydrocarbons, otherwise they would accumulate in the atmosphere indefinitely,” Nizkorodov said. it’s a statement.
“OH is a key player in the history of atmospheric chemistry. It initiates the reactions that break down air pollutants and helps remove harmful chemicals such as sulfur dioxide and nitric oxide, which are poisonous gases, from the atmosphere,” he said. Christian George, an atmospheric chemist at the University of Lyon in France and lead author of the new study. “Therefore, having a full understanding of its sources and sinks is key to understanding and mitigating air pollution.”
Previously, researchers assumed that sunlight was the main driver of OH formation.
“The conventional wisdom is that you have to make OH by photochemistry or redox chemistry. You have to have sunlight or metals acting as catalysts,” Nizkorodov said. “What this document essentially says is that you don’t need any of this. In pure water, OH can be created spontaneously by special conditions on the surface of the droplets.”
The team built on research by Stanford University scientists led by Richard Zare that reported the spontaneous formation of hydrogen peroxide on the surface of water droplets. The new findings help interpret the unexpected results from the Zare group.
The team measured OH concentrations in different vials, some containing a surface of air and water and others containing just water without air, and tracked the production of OH in the dark by including a “probe” molecule in the vials that fluoresces when reacted with OH.
What they saw is that the rates of OH production in the dark mirror those and even exceed the rates of conductors such as exposure to sunlight. “Enough OH will be created to compete with other known sources of OH,” Nizkorodov said. “At night, when there’s no photochemistry, OH is still being produced, and it’s being produced at a higher rate than it would otherwise.”
The findings, Nizkorodov reported, alter the understanding of the sources of OH, something that will change the way other researchers they build computer models that try to forecast how air pollution occurs.
“It could change air pollution patterns quite significantly,” Nizkorodov said. “OH is a major oxidant within water droplets and the main assumption in the models is that OH comes from the air, not produced directly in the droplet.”
To determine if this new OH production mechanism plays a role, Nizkorodov believes the next step is to perform experiments. carefully designed in the real atmosphere in different parts of the world.
