A new scientific finding may help better understand how to tackle greenhouse gas pollution. The key is in a compound called the hydroxyl radical (OH), which acts as a “detergent” from the air, removing harmful gases.
Human activities emit many types of pollutants into the air, and if it were not for the hydroxyl (OH) radicals, which are composed of a hydrogen and an oxygen atom, they would continue to accumulate in the atmosphere in larger quantities than they do now.
This compound acts by cleaning the air, ‘breaking’ other gases. Especially, OH is the main control of methane concentration, It is a powerful greenhouse gas that ranks second after carbon dioxide in terms of its contribution to global warming.
How OH forms in the atmosphere was long thought to be known, but new research by a group of scientists, including Sergey Nizkorodov, a professor of chemistry at the University of California at Irvine, found that: A strong electric field that exists between the water droplets and the surrounding air can create OH by a hitherto unknown mechanism.. Results published Proceedings of the National Academy of Sciences.
This finding gives us a better understanding of how the air is cleaned of pollutants that OH can react and remove, such as those emitted by humans and greenhouse gases.. “OH is required to oxidize hydrocarbons, otherwise they will accumulate in the atmosphere indefinitely.” Nikorodov remembered.
“OH is a key player in the history of atmospheric chemistry. It initiates reactions that break down air pollutants and helps remove harmful chemicals from the atmosphere, such as toxic gases sulfur dioxide and nitric oxide,” said Christian George. 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 reducing air pollution,” he added.
Produced directly in water droplets
Previously, researchers hypothesized that sunlight was the main driver of OH formation.“Conventional wisdom was that you get the OH by photochemistry or redox chemistry. You have to have sunlight or metals that act as catalysts,” Nizkorodov said. “But what this study basically says is that you don’t need any of that. OH can occur spontaneously in pure water. by the special conditions on the surface of the drops”.
The team relied on research by Stanford University scientists led by Richard Zare. revealed spontaneous generation of hydrogen peroxide on the surface of water droplets. The new findings help interpret unexpected results from the Zare group.
The team measured OH concentrations in different bottles, some containing air and water surface, and others containing only airless water, and added a “probe” molecule to the bottles that fluoresces when reacted with OH, measuring OH production in the dark.
What they see is that rates of OH production in the dark even exceed rates of conductors like exposure to sunlight. “At night, in the absence of photochemistry, OH is still produced. and it happens at a higher rate than it would otherwise,” Nizkorodov added.
According to him, this discovery changes the knowledge about the sources of OH, which in turn will change the way other researchers build computer models to predict how air pollution occurs.
“It can change air pollution patterns quite significantly,” Nizkorodov said. Said. “OH is an important oxidant in water droplets. And the main assumption in the models is that the OH comes from the air, not produced directly in the droplet.”
To determine whether this new OH production mechanism plays a relevant role, Nizkorodov believes: The next step should be to conduct carefully designed experiments in real atmosphere. in different parts of the world.
But first, the team hopes the results will be accepted by atmospheric scientists. “A lot of people will read this, but initially they won’t believe it and will try to reproduce it or do experiments to prove it wrong,” Nizkorodov said. Said.
Reference work: https://www.pnas.org/doi/10.1073/pnas.2220228120
……..
Contact address of the environment department: [email protected]