Nav: Home

Iodine may slow ozone layer recovery

January 13, 2020

A new paper quantifying small levels of iodine in Earth's stratosphere could help explain why some of the planet's protective ozone layer isn't healing as fast as expected.

The paper posits a set of connections that link air pollution near Earth's surface to ozone destruction much higher in the atmosphere. That higher-level ozone protects the planet's surface from radiation that can cause skin cancer and damage crops.

"The impact is maybe 1.5 to 2 percent less ozone," said lead author Theodore Koenig, a postdoctoral researcher at CIRES and the University of Colorado Boulder, referring to ozone in the lower part of the ozone layer, around Earth's tropics and temperate zones. "That may sound small, but it's important," he said.

A slightly thinner ozone layer means more UVB radiation can get through to Earth's surface.

Koenig's paper, the first "quantitative detection" of iodine in the stratosphere, is published this week in the Proceedings of the National Academy of Sciences, with co-authors from CIRES, CU Boulder and other institutions.

Chemicals once used widely in refrigeration, spray cans and solvents can eat away at Earth's ozone layer. After scientists discovered the stratospheric "ozone hole" in the 1980s, nations around the world signed the international Montreal Protocol agreement to protect the ozone layer, limiting the emission of ozone-depleting chemicals.

"The ozone layer is starting to show early signs of recovery in the upper stratosphere, but ozone in the lower stratosphere continues to decline for unclear reasons," said Rainer Volkamer, a CIRES Fellow, CU Boulder professor of chemistry and corresponding author of the new assessment.

"Before now, the decline was thought to be due to changes in how air mixes between the troposphere and stratosphere. Our measurements show there is also a chemical explanation, due to iodine from oceans. What I find exciting is that iodine changes ozone by just enough to provide a plausible explanation for why ozone in the lower stratosphere continues to decline."

For the new work, Volkamer and his colleagues pored through data from several recent atmospheric research campaigns involving U.S. National Science Foundation (NSF) and NASA research aircraft, and which included instruments that could pick up tiny amounts of iodine and other so-called halogens in the lower stratosphere during the daytime. Halogens, which also include chlorine and bromine, are key to ozone destruction.

It's been tricky to get data from this part of the atmosphere, Koenig said. "We knew there was some iodine there, but we couldn't pin numbers on it until now... This is a result of technological advancement: Our instruments just kept getting a little bit better and eventually, it was enough to make measurements."

The amount of iodine they picked up in the lower stratosphere is tiny, similar to adding a few bottles of water to the Great Salt Lake. But iodine is extremely effective at destroying ozone, and, generally speaking, the amount the scientists measured is enough to explain the level of ozone destruction in the lower stratosphere.

So where did the iodine come from? Strangely it seems to be a result of air pollution down here at the surface of the planet, the new assessment reports.

Ozone at Earth's surface is a pollutant, one that is regulated in the United States and elsewhere because it can harm people's lungs. And when ozone pollution interacts chemically with the surface of oceans, it can "pull" naturally occurring iodine up into the atmosphere. Other studies have shown that in the lower atmosphere, iodine levels have roughly tripled in concentration since 1950.

Some of that iodine is apparently making it up into the stratosphere, where it can trigger ozone depletion, Koenig said. "This should not diminish the success story of the Montreal Protocol, but still, it is important. The lower stratosphere should have improved already, not gotten worse."

"There's something going on resulting in deterioration. Our hypothesis is that ozone at the surface is destroying ozone in the stratosphere," Koenig added.

It will be important to study the hypothesis in greater detail, Koenig and his coauthors said. If ozone pollution at Earth's surface increases, for example, could it trigger even more lower-stratosphere ozone layer destruction?

Coauthor Pedro Campuzano-Jost, a CIRES research associate, said the success of the research project is partly due to the unique scope of NASA's ATom (Atmospheric Tomography) mission, which flew a research aircraft across the globe; and NSF's CONTRAST (Convective Transport of Active Species in the Tropics) mission, which detected iodine oxide radicals in the stratosphere.

"Half of the places we went had never been sampled before for aerosols," Campuzano-Jost said, and that is the kind of opportunity that leads to new discoveries.

Volkamer and his colleagues hope to successfully pitch a new mission to study iodine chemistry in greater detail, to better understand the future of Earth's protective ozone layer.
-end-


University of Colorado at Boulder

Related Air Pollution Articles:

Air pollution linked to dementia and cardiovascular disease
People continuously exposed to air pollution are at increased risk of dementia, especially if they also suffer from cardiovascular diseases, according to a study at Karolinska Institutet in Sweden published in the journal JAMA Neurology.
New framework will help decide which trees are best in the fight against air pollution
A study from the University of Surrey has provided a comprehensive guide on which tree species are best for combating air pollution that originates from our roads -- along with suggestions for how to plant these green barriers to get the best results.
Air pollution is one of the world's most dangerous health risks
Researchers calculate that the effects of air pollution shorten the lives of people around the world by an average of almost three years.
The world faces an air pollution 'pandemic'
Air pollution is responsible for shortening people's lives worldwide on a scale far greater than wars and other forms of violence, parasitic and insect-born diseases such as malaria, HIV/AIDS and smoking, according to a study published in Cardiovascular Research.
New study examines mortality costs of air pollution in US
Scholars from the Gies College of Business at Illinois studied the effects of acute fine particulate matter exposure on mortality, health care use and medical costs among older Americans through Medicare data and changes in local wind direction.
Air pollution in childhood linked to schizophrenia
Children who grow up in areas with heavy air pollution have a higher risk of developing schizophrenia.
Air pollution can worsen bone health
A new study by the CHAI Project with over 3,700 people in India associates air pollution with a higher risk to develop osteoporosis.
Depression and suicide risk linked to air pollution
People exposed to higher levels of air pollution are more likely to experience depression or die by suicide, finds a new analysis led by UCL, published in Environmental Health Perspectives.
Air pollution linked with new causes of hospital admissions
Several diseases have been linked for the first time with exposure to short-term air pollution.
Air pollution linked to several new causes of hospital admissions
Short term exposure to fine particulate matter in the air (known as PM2.5) is associated with several newly identified causes of hospital admissions, even at levels below international air quality guidelines, finds a US study published by The BMJ today.
More Air Pollution News and Air Pollution Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Teaching For Better Humans 2.0
More than test scores or good grades–what do kids need for the future? This hour, TED speakers explore how to help children grow into better humans, both during and after this time of crisis. Guests include educators Richard Culatta and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Space
One of the most consistent questions we get at the show is from parents who want to know which episodes are kid-friendly and which aren't. So today, we're releasing a separate feed, Radiolab for Kids. To kick it off, we're rerunning an all-time favorite episode: Space. In the 60's, space exploration was an American obsession. This hour, we chart the path from romance to increasing cynicism. We begin with Ann Druyan, widow of Carl Sagan, with a story about the Voyager expedition, true love, and a golden record that travels through space. And astrophysicist Neil de Grasse Tyson explains the Coepernican Principle, and just how insignificant we are. Support Radiolab today at Radiolab.org/donate.