Oceans Absorb and Remove 15 Percent of Nitrogen Oxide from Air, Study


A recent University of California San Diego study has found that besides regulating temperatures and weather patterns, oceans help cleanse the air as well.

Researchers said that the surface of the sea has the ability to eliminate about 15 percent of the smog-forming nitrogen oxides (accumulated in polluted air) along the coast overnight.

Vehicle tailpipes, factories, trains and ships release nitrogen oxides. The gases that are produced by burning fossil fuels react with sunlight to form ozone, or photochemical smog. Although the nitrogen oxide emissions continue at night, the chemical reactions are different, according to the lead researcher Tim Bertram, an assistant professor of chemistry.

"One often neglected path is reaction at the surface of the sea," Bertram said in a press release. "The sea has a salty, rich, organic surface with the potential for a variety of chemical reactions."

The study is based on measurements on the coast of southern California. The researchers deployed scientific instruments at the Scripps Institution of Oceanography pier last year to measure the flow of the nitrogen oxide molecules.

During one night in February, when winds transported a polluted air mass from the Los Angeles Basin along the coast, the researchers tracked nitrogen oxide gases as they swept across the surface of the sea, Los Angeles Times reports.

Bertram expected the pollutants to react at the ocean surface to form other compounds. Much to his surprise, no reactions occurred. "As soon as it's lost to the ocean surface it's gone," Bertram said.

The observation showed that ocean water is a 'terminal sink' for nitrogen oxides, permanently removing gases from the air.

"We knew from previous work that nitrogen oxides are lost to various surfaces - sea spray and other aerosols, even snowpack," Michelle Kim, a graduate student at UC San Diego's Scripps Institution of Oceanography, said. "This study shows - for the first time - that the ocean is a terminal sink for nocturnal nitrogen oxides, and not a source for nitryl chloride under these sampling conditions."

This is a significant finding because most of the world's nitrogen oxide pollution is released near salt water bodies.

The finding is published in the Proceedings of the National Academy of Sciences.

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