New research has found that the atmosphere can clean itself by a molecule called hydroxide (OH) and through a previously unknown mechanism. Hydroxide oxidizes many gases released into the air from natural processes and human activity and breaks them down into water-soluble substances, which can be cleaned and removed from the atmosphere.
Until now, scientists believed that hydroxide was formed mainly by sunlight, but the new study published in the Proceedings of the National Academy of Sciences revealed that the electric field that exists in the area between the air and water droplets carried in the air can also create the molecules. The professor of chemistry from the University of California, a member of the research team, Sergey Nizkorodov, noted that “Until now, we thought that in order to create OH, photochemistry or oxidation was needed. However, this study found that both are not needed. In pure water, OH can be created spontaneously under special conditions that form on the surface of the droplets.”
The team of researchers built on previous research by a team of scientists from Stanford University who found hydrogen peroxide (H2O2) to form spontaneously on the surface of water droplets. The team conducted the study by measuring OH concentrations in different vials, some containing an air-water interface and others containing only water without air.
Then monitor OH production in the dark by including a “probe” molecule that lights up when it reacts with OH. The scientists found that OH production rates in the dark were the same or even higher than in situations such as exposure to sunlight. “At night, when there is no photochemistry, OH is still produced and at a higher rate,” Nizkorodov said.
Chemist and author of the study, Christian George explained that “OH is a key player in atmospheric chemistry. It initiates the reactions that break down airborne pollutants and helps remove harmful chemicals such as sulfur dioxide and nitrogen oxide, which are toxic gases, from the atmosphere. Therefore, a full understanding of Its sources and sinks is the key to reducing air pollution.”
The team noted that the new findings change the understanding of the sources of OH and will affect how researchers build computer models to predict air pollution. “This could change air pollution models quite significantly,” Nizkorodov said. “OH is an important oxidant within water droplets and the main assumption in the models is that OH comes from the air and is not produced in the droplets.” Nizkorodov added that the next step should be to carry out carefully planned experiments in the open air in different parts of the world.
Researchers from the Weizmann Institute, Claude Bernard University in France and Guangdong University of Technology in China also participated in the study, which was funded by the European Research Council.