Scientists have detected a new type of extremely reactive substance in the Earth’s atmosphere that could pose a threat to human health, as well as to the global climate.
Researchers from the University of Copenhagen have shown that trioxides – chemical compounds with three oxygen atoms attached to each other – form under atmospheric conditions.
Trioxides are even more reactive than peroxides – which have two oxygen atoms attached to each other, making them highly reactive and often flammable and explosive.
Peroxides are known to exist in the air around us, and it has been predicted that trioxides were probably also in the atmosphere, but so far this has never been unequivocally proven.
‘We have now achieved that,’ says Professor Henrik Grum Kjærgaard, from the Department of Chemistry at the University of Copenhagen.
“The types of compounds we discovered are unique in their structure. And, because they’re extremely oxidative, they most likely bring about a whole host of effects we haven’t discovered yet.
Scientists have detected a new type of highly reactive substance in Earth’s atmosphere that could pose a threat to human health, as well as the global climate
When chemical compounds are oxidized in the atmosphere, they often react with OH radicals, usually forming a new radical. When this radical reacts with oxygen, it forms a third radical called peroxide (ROO), which in turn can react with the OH radical, forming hydrotrioxides (ROOOH). Reaction: ROO + OH → ROOOH
How do hydrotrioxides form?
When chemical compounds are oxidized in the atmosphere, they often react with OH radicals, usually forming a new radical.
When this radical reacts with oxygen, it forms a third radical called peroxide (ROO), which in turn can react with the OH radical, forming hydrotrioxides (ROOOH).
Reaction: ROO + OH → ROOOH
The specific trioxides they detected – called hydrotrioxides (ROOOH) – are an entirely new class of chemical compounds.
Hydrotrioxides are formed during a reaction between two types of radicals (molecules containing at least one unpaired electron).
In laboratory experiments – using a free-jet flow tube at room temperature and 1 bar air pressure, combined with highly sensitive mass spectrometers – researchers demonstrated that hydrotrioxides are formed when the atmospheric breakdown of several known and widely emitted substances, including isoprene and dimethyl sulfide.
Isoprene is one of the most frequently emitted organic compounds into the atmosphere. It is produced by many plants and animals and its polymers are the main component of natural rubber.
The study shows that about one percent of all isoprene released turns into hydrotrioxides.
However, researchers expect almost all chemical compounds to form hydrotrioxides in the atmosphere and estimate their lifetimes to range from minutes to hours.
This makes them stable enough to react with many other atmospheric compounds.
Researchers estimate the concentrations of hydrotrioxides in the atmosphere to be around 10 million per cubic centimeter.
By comparison, OH radicals (one of the most important oxidants in the atmosphere) are found at concentrations of about one million per cubic centimeter.
“We can now show, by direct observation, that these compounds actually form in the atmosphere, that they are surprisingly stable, and that they are formed from almost all chemical compounds,” said Jing Chen, a doctoral student at the department of chemistry and second author of the study.
“All speculation must now be put to rest.”
Laboratory installation of the free-jet flow experiment, which provided the first direct evidence that the formation of hydrotrioxides (ROOOH) also takes place under atmospheric conditions.
The research team says hydrotrioxides are likely to enter tiny airborne particles, called aerosols, which pose a health risk and can lead to respiratory and cardiovascular disease.
“They will most likely enter aerosols, where they will form new compounds with new effects,” Prof Kjærgaard said.
“It’s easy to imagine new substances forming in the aerosols that are harmful if inhaled. But further investigation is needed to address these potential health effects.
There is also a high likelihood that hydrotrioxides will impact the number of aerosols produced, the researchers say, which in turn impacts climate.
“As sunlight is both reflected and absorbed by aerosols, this affects the Earth’s heat balance, that is, the ratio of sunlight that the Earth absorbs and reflects back into the space,” explained the co-author and PhD. student Eva R. Kjærgaard.
“When aerosols absorb substances, they expand and contribute to cloud formation, which also affects Earth’s climate.”
Researchers hope the discovery of hydrotrioxides will help scientists learn more about the effect of the chemicals we emit.
“Most human activities result in the emission of chemicals into the atmosphere,” said co-author and post-doctoral fellow Kristan H. Møller.
“Thus, knowledge of the reactions that determine atmospheric chemistry is important if we are to be able to predict how our actions will affect the atmosphere in the future.”
Professor Kjærgaard added: “These compounds have always existed – we just didn’t know about them.
“But the fact that we now have evidence that the compounds form and live for a period of time means that it is possible to study their effect in a more targeted way and to react if they turn out to be dangerous.”
The study was published in the journal Science.
The Moon may have been siphoning water from Earth’s atmosphere for billions of years
The moon may have siphoned water from Earth’s atmosphere for billions of years, storing it as ice at the bottom of craters, a new study has found.
Research from the University of Alaska Fairbanks suggests that the ions that make up water are attracted to the moon as it passes through part of Earth’s magnetosphere.
This is in addition to other suspected methods including the bombardment of asteroids 3.5 billion years ago and the solar wind delivering oxygen and hydrogen ions.
The team estimates that there are up to 840 cubic miles of surface permafrost or underground liquid water on the moon that have escaped from Earth’s atmosphere – enough to fill Lake Huron in North America – the eighth largest lake on the planet.
The work, by lead author Professor Gunther Kletetschka, adds to a growing body of research on water at the moon’s north and south poles, prime targets for a base.
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