Wildfires send smoke into the stratosphere where particles can remain adrift for a year or more, ultimately damaging the ozone layer.
A new study from the Massachusetts Institute of Technology (MIT) in the United States shows that while these particles are floating, they can cause chemical reactions in the layers of gas that protect the Earth from harmful ultraviolet rays from the sun. rice field.
The study, published in the journal Nature, focuses on the smoke from the Black Summer megafire in eastern Australia between December 2019 and January 2020. Over one million tons of smoke were released into the atmosphere.
A team at MIT has identified a new chemical reaction in Australian wildfire smoke particles that exacerbates the depletion of the ozone layer. By triggering this reaction, fires may have contributed to the depletion of 3–5% of total ozone in the mid-latitudes of the Southern Hemisphere, Australia, New Zealand, and parts of Africa and South America.
The researchers’ modeling also shows that the fires affected the polar region and eroded the edge of the ozone hole over Antarctica. At the end of 2020, smoke particles from the Australian wildfires expanded the Antarctic ozone hole by 2.5 million square kilometers of her. This is 10% of its area compared to the previous year.
It is unclear what long-term effects wildfires will have on ozone recovery.
The United Nations recently reported that the ozone hole and global ozone depletion are improving thanks to sustained international efforts to phase out ozone-depleting chemicals.
But the MIT study suggests that as long as these chemicals remain in the atmosphere, large fires can trigger reactions that temporarily deplete ozone.
“The 2020 Australian wildfires were just a wake-up call to the scientific community,” said Lee and Geraldine Martin, a professor of environmental studies at the Massachusetts Institute of Technology who is responsible for the crater. Susan Solomon, the leading climatologist who first identified the chemical, said…
“The impact of wildfires has not previously been considered in projections of ozone recovery,” he admits, adding that “the impact could depend on whether fires become more frequent and intense as the planet warms.” I think it has potential.”
Conducted by Solomon and MIT graduate student Peidong Wang, the new study, along with collaborators from the Guangzhou Environmental and Climate Research Institute, the National Oceanic and Atmospheric Administration, the National Center for Atmospheric Research, and Colorado State University, will be announced by Solomon and colleagues in 2022. discovered and identified for the first time a chemical link between wildfires and ozone depletion.
They found that chlorine-containing compounds, originally released from factories in the form of chlorofluorocarbons (CFCs), can react with surfaces in fire aerosols. This interaction triggered a chemical cascade that produced chlorine monoxide, the molecule most depleting the ozone layer. Their results indicated that the Australian wildfires likely depleted ozone through this newly identified chemical reaction.
“But it didn’t explain all the changes we observed in the stratosphere. There were a lot of chlorine-related chemistries that were completely off the mark,” Solomon admits.
In a new study, the team delved into the molecular composition of the stratosphere after wildfires in Australia. They looked at his three independent satellite data and found that in the months after the fire, there was a sharp decline in hydrochloric acid concentrations and an increase in chlorine monoxide concentrations in the mid-latitudes.
Hydrochloric acid (HCl) exists in the stratosphere and CFCs naturally degrade over time. Chlorine has no potential to destroy ozone as long as he is bound in the form of HCl. However, when HCl decomposes, chlorine reacts with oxygen to form chlorine monoxide, which destroys the ozone layer.
In the polar regions, HCl can decompose by interacting with the surface of cloud particles at frigid temperatures of about 155 Kelvin. However, this reaction was not expected to occur in mid-latitudes, where temperatures are much higher.
So Solomon wondered if HCl interacted with smoke particles at high temperatures, releasing chlorine and destroying ozone. If such a reaction were possible, it would explain much of the molecular imbalance and ozone depletion observed after the Australian wildfires.
The team searched the chemical literature to see what kinds of organic molecules could react with HCl and decompose at higher temperatures. “We found that HCl is very soluble in a wide range of organic species. It likes to stick to many compounds,” he recalls.
The question was whether the Australian wildfires released compounds that may have caused the decomposition of HCl and consequent ozone depletion.
When the team analyzed the composition of smoke particles in the first days after the fire, the picture was far from clear.
“I looked at these things and put my hand to my head and thought, ‘There are so many things out there and how can I find them,'” recalls Solomon. Now that we’ve seen a decrease in HCl, we really need to see the old particle data from wildfires. “
Expanding their investigation, the team found that the smoke particles persisted for months and circulated in the same region of the mid-latitude stratosphere during periods of low HCl concentration.
“It’s the old smoke particles that actually absorb most of the HCl. Then, surprisingly, you get the same response as the ozone hole, but at much higher temperatures in the mid-latitudes.”
When the team incorporated this new chemistry into an atmospheric chemistry model to simulate wildfire conditions in Australia, they found a 5% reduction in ozone across the mid-latitude stratosphere and a 10% increase in the ozone hole above Antartida. Observed.
Reaction with HCl is probably the main pathway by which forest fires deplete the ozone layer. But Solomon speculates that there may be other chlorine-containing compounds drifting into the stratosphere, which wildfires could unleash.
“Right now we are in a kind of race against time. I hope that the chlorine-containing compounds are destroyed before climate change increases the frequency of fires. All the more reason to pay attention to warming containing compounds.
Source: Diario.Elmundo
