Havard professor says aerosols in space could cool planet
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Peroxides are a class of chemical compounds which feature two oxygen atoms linked together by a single covalent bond, a setup which makes them highly reactive and, in many cases, flammable and explosive as well. They are used for assorted applications, from bleaching hair and whitening teeth to cleaning wounds and even for fuelling rockets. Compounds with three oxygen atoms, meanwhile, are called trioxides — and they are even more reactive than their peroxide cousins.
Scientists have long known that peroxides can be found in the air around us, leading to speculation that perhaps trioxides might also exist in the atmosphere as well — but experts had never been able to prove this unequivocally.
Paper author and atmospheric chemist Professor Henrik Grum Kjærgaard, of the University of Copenhagen, said: “This is what we have now accomplished.
“The type of compounds we discovered are unique in their structure. And, because they are extremely oxidising, they most likely bring a host of effects that we have yet to uncover.”
The specific compounds the team detected are so-called hydrotrioxides, which can form under atmospheric conditions.
The researchers were able to show that hydrotrioxides are formed in the atmosphere during the decomposition of several widely emitted substances.
These include isoprene, which is produced by many plants and animals, and dimethyl sulfide, which is released by certain types of marine plankton.
In fact, the researchers said, around one percent of all isoprene released turns into hydrotrioxides.
The team have calculated that the atmospheric concentration of hydrotrioxides is likely around 10 million for every cubic centimetre.
Paper author and chemist Jing Chen, also of the University of Copenhagen, said: “It’s quite significant that we can now show, through direct observation, that these compounds actually form in the atmosphere.”
Hydrotrioxides, she added, are “surprisingly stable and that they are formed from almost all chemical compounds. All speculation must now be put to rest.”
According to the team, hydrotrioxides have lifespans that range from minutes to hours — meaning that they are stable enough to react with many other atmospheric compounds.
The researchers also believe that trioxides are likely able to penetrate into aerosols — tiny airborne particles that can lead to cardiovascular and respiratory diseases.
Prof. Kjærgaard said: “They will most likely enter aerosols, where they will form new compounds with new effects.
“It is easy to imagine that new substances are formed in the aerosols that are harmful if inhaled. But further investigation is required to address these potential health effects.”
Aerosols are known to also have an impact on the climate — but are among the most difficult things to describe in climate models.
Paper co-author and atmospheric chemist Eva Kjærgaard said: “As sunlight is both reflected and absorbed by aerosols, this affects the Earth’s heat balance — that is, the ratio of sunlight that Earth absorbs and sends back into space.
“When aerosols absorb substances, they grow and contribute to cloud formation, which affects Earth’s climate as well.”
According to the team, there is a high probability that hydrotrioxides have an impact on how many aerosols are produced.
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The researchers also believe that trioxides are likely able to penetrate into aerosols — tiny airborne particles that can lead to cardiovascular and respiratory diseases.
Prof. Kjærgaard said: “They will most likely enter aerosols, where they will form new compounds with new effects.
“It is easy to imagine that new substances are formed in the aerosols that are harmful if inhaled. But further investigation is required to address these potential health effects.”
Aerosols are known to also have an impact on the climate — but are among the most difficult things to describe in climate models.
Paper co-author and atmospheric chemist Eva Kjærgaard said: “As sunlight is both reflected and absorbed by aerosols, this affects the Earth’s heat balance — that is, the ratio of sunlight that Earth absorbs and sends back into space.
“When aerosols absorb substances, they grow and contribute to cloud formation, which affects Earth’s climate as well.”
According to the team, there is a high probability that hydrotrioxides have an impact on how many aerosols are produced.
The researchers have stressed that they are not concerned about their discoveries.
Prof. Kjærgaard explained: “These compounds have always been around — we just didn’t know about them.
“But the fact that we now have evidence that the compounds are formed and live for a certain amount of time means that it is possible to study their effect more targeted and respond if they turn out to be dangerous.”
Ms Chen added: “The discovery suggests that there could be plenty of other things in the air that we don’t yet know about.
“Indeed, the air surrounding us is a huge tangle of complex chemical reactions.
“As researchers, we need to keep an open mind if we want to get better at finding solutions.”
The full findings of the study were published in the journal Science.
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