Iodine in desert dust destroys ozone layer: Study


New Delhi: According to one study, when winds lift fine desert dust up into the atmosphere, the iodine in that dust can trigger chemical reactions that destroy some air pollution, but allow greenhouse gases to remain for longer. .

This research is published in the ‘Science Advances Journal’. “Iodine, the same chemical that’s added as a nutrient to table salt, is eating up the ozone in the dusty air in the atmosphere,” said Rainer Volkmar, a CIRES Fellow and professor of chemistry at CU Boulder.

Volkamer led the team that several years ago made precise atmospheric measurements by aircraft over the eastern Pacific Ocean. The new discovery, he said, has implications not only on air quality, but also on the climate – iodine chemistry can make greenhouse gases long-lasting and should give us pause to rethink geoengineering plans involving dust.
“Our understanding of the iodine cycle is incomplete,” Volkmar said.

“There are land-based sources and chemistry that we didn’t know about that we should consider now,” Volkmar said.
Atmospheric researchers have long been interested in the observation that dusty layers of air are often very low in the air pollutant ozone, which, when concentrated, can damage people’s lungs and even crops. . It seemed that some sort of dust-surface chemical was devouring the ozone, but no one was able to show this in laboratory experiments.
Others have speculated about this, but there is much doubt, Volkmar said. In contrast, laboratory experiments have long shown that a gaseous form of iodine can swallow ozone – but there were only indications of a connection between dust and iodine.

There were other tantalizing clues about the process in a dataset from 2012, from a series of aircraft flights offshore Chile and Costa Rica. The level of gaseous iodine was remarkable in the dust flying offshore from South America. Volkemer handed over the data to the study’s lead author, then-CU Boulder graduate student Theodor Koenig.

Koenig described those data as a set of blurry pictures shared by atmospheric chemists around the world. In one image, for example, “iodine seemed to be correlated with dust … but not quite as clearly,” he said.
Everywhere, dust seemed to destroy ozone, but why?

“Iodine and ozone clearly associate, but there was no ‘photo’ of the two with dust,” said Koenig, who is now an air pollution researcher at Peking University in China.

Data from TORERO (“Tropical Ocean Troposphere Exchange of Reactive Halogen and Oxygenated Hydrocarbons,” a field expedition funded by the National Science Foundation) held those three characters together, ultimately, in one image, he said, and it was clear. that where desert dust contains significant levels of iodine – such as dust from the Atacama and Sechura deserts in Chile and Peru – iodine quickly converted to a gaseous form and ozone depleted to very low levels. But how did that dust-based iodine turn up?

“The mechanism still remains elusive,” Volkmar said.

“This is the work of the future,” Volkmar said.

So the picture is a more blurry one, Koenig said, but even so, science is faster than it used to be.

“I have more questions at the end of the project than at the beginning. But those are better, more specific questions,” he said.
They are also very important, for anyone interested in the future of the atmosphere, Volkmar said. Reactions of iodine in the atmosphere are known to play a role in reducing OH levels, for example, which can increase the lifetime of methane and other greenhouse gases. Perhaps more importantly, various geoengineering ideas included injecting dust particles high enough into the Earth’s atmosphere to reflect incoming solar radiation. There, in the stratosphere, ozone is not a pollutant; Rather, it forms an important “ozone layer” that helps shield the planet from incoming radiation.

If the iodine from the dust was chemically converted to an ozone-depleting form in the stratosphere, Volkemer said, “Well, that wouldn’t be good, because that might delay the recovery of the ozone layer. Let’s look at anthropogenic iodine.” Avoid adding to the stratosphere!” (ANI)

First published:December 26, 2021, 11:24 am

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