Millions of tonnes of a class of extremely reactive chemicals called hydrotrioxides can linger in the atmosphere for several hours, a new study has found, which could have implications for human health and the global climate.
Chemicals interact extremely quickly with other compounds, and their presence means chemists will have to rethink how processes occur in the atmosphere.
Hydrotrioxides – chemical compounds containing one hydrogen atom and three oxygen atoms – have long been thought to be too unstable to last long in atmospheric conditions.
But the new research instead shows that hydrotrioxides are a regular product of many common chemical reactions and can remain stable enough to react with other compounds in the atmosphere.
“We showed that the lifetime of one of them was at least 20 minutes,” Henrik Grum Kjærgaard, a chemist at the University of Copenhagen, told Live Science. “So it’s long enough for them to do stuff in the atmosphere.”
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Kjærgaard is one of the authors of a new study on the formation of hydrotrioxide in the atmosphere published online May 26 in the Science magazine (opens in a new tab).
Discovery does not mean that something new is happening in the atmosphere; rather, it seems that hydrotrioxides have always formed there. But the new study is the first time the existence of these ultra-reactive chemicals in the atmosphere has been verified.
“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 any chemical compound,” said Jing Chen, a doctoral student at the University of Copenhagen, second author of the study. , said in a press release (opens in a new tab). “All speculation must now be put to rest.”
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Powerful oxidants
Hydrotrioxides are a type of hydrogen polyoxide. Water is the simplest and most common hydrogen polyoxide, with two hydrogen atoms and one oxygen atom, or H2O.
Another hydrogen polyoxide is hydrogen peroxide, which has two oxygen atoms – H2O2 – and is commonly used as a bleach or disinfectant. The extra oxygen atom also makes many peroxides extremely flammable, and they are sometimes used as a component of rocket fuels.
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Hydrotrioxides are a step further, as they have three oxygen atoms attached to each other, which makes them even more reactive than peroxides. They are written chemically as ROOOH, where R is any bonded group, such as a carbon band.
But while it is known that peroxides can form from chemical reactions in the atmosphere, it was not previously known that hydrotrioxides can also form there, albeit for a relatively short time before breaking down into less reactive chemicals.
In the new study, the researchers estimate that approximately 11 million tonnes (10 million metric tons) of hydrotrioxides are formed in the atmosphere each year as a product of one of the most common reactions: oxidation. isoprene, a substance produced by many plants and animals and which is the main component of natural rubber.
Researchers estimate that about 1% of isoprene released into the atmosphere forms hydrotrioxides, and that they are produced from these reactions at very low concentrations – about 10 million hydrotrioxide molecules in one cubic centimeter. of the atmosphere, which is only a very faint trace.
“We are very happy to have been able to show that [hydrotrioxides] are there and that they live long enough to be – very likely – important in the atmosphere,” said study lead author Torsten Berndt, an atmospheric chemist at the Leibniz Institute for Tropospheric Research (TROPOS) at Leipzig, Germany to Live Science in an email.
Atmospheric experiments
Berndt led the research laboratory experiments at TROPOS to find out if hydrotrioxides were in fact produced by chemical reactions in the atmosphere, while the University of Copenhagen team studied the theoretical aspects of hydrotrioxide formation .
Berndt and his colleagues used highly sensitive mass spectrometry to detect ultra-reactive hydrotrioxides – a technique that can determine the molecular weight of chemicals to find out what atoms they are made of.
The reactions to make the hydrotrioxides took place in the TROPOS free-jet flow system (opens in a new tab)which creates an airflow unobstructed by solid walls.
And the study also used results from experiments in an atmospheric chamber at the California Institute of Technology in Pasadena.
Now that their research has confirmed that hydrotrioxides are formed by common chemical reactions in the atmosphere, the scientists will next investigate how the compounds could affect human health and the environment during the minutes or hours of activity before the compounds don’t break down, Berndt said.
“From the knowledge of organic chemistry, one may expect that [hydrotrioxides] will act as an oxidant in the atmosphere,” he said. It’s also possible that hydrotrioxides have an effect when our lungs breathe air that contains them at very low concentrations, “but all of that is very speculative at the moment”.
Berndt said hydrotrioxides can also enter atmospheric aerosols — very fine solid particles or liquid droplets suspended in the atmosphere, such as ash from volcanic eruptions or soot from large fires — and could trigger chemical reactions. But “experimental investigations of this are very difficult,” he said. “It’s a lot to do.”
Originally published on Live Science.
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