An international team has detected the presence in the Earth’s atmosphere of a new class of extremely oxidizing chemical compound, ‘trioxides’, which is suspected of influencing the climate and air quality.
Researchers from the University of Copenhagen (UCPH), together with scientists from the Leibniz Institute for Tropospheric Research (TROPOS) and the California Institute of Technology (Caltech), have detected the presence in the atmosphere of a new class of extremely oxidizing chemical compound , the ‘trioxides’.
A commonly known chemical compound is hydrogen peroxide. All peroxides have two oxygen atoms bonded to each other, making them highly reactive and often flammable and explosive.
They are used for everything from whitening teeth and hair, to cleaning wounds, and even as rocket fuel. But peroxides are also found in the air around us.
In recent years, there has been speculation about whether trioxideschemical compounds with three oxygen atoms bonded together and thus even more reactive than peroxides, are also found in the atmosphere. But until now, it had never been unequivocally confirmed and this is what the new investigation, led by Henrik Grum Kjaergaardfrom the Department of Chemistry at the University of Copenhagen.
New chemical compounds
The hydrotrioxides (ROOOH), as trioxides are more technically known, are an entirely new class of chemical compounds. New research has shown that they form under atmospheric conditions.
The researchers estimate that concentrations of ROOOH in the atmosphere are about 10 million per cubic centimeter. By comparison, OH radicals, one of the most important oxidants in the atmosphere, are found at about 1 million radicals per cubic centimeter.
Researchers have also shown that hydrotrioxides form during the atmospheric decomposition of several known and widely emitted substances, including isoprene and dimethyl sulfide.
Hydrotrioxides are formed in a reaction between two types of radicals. Researchers believe that almost all chemical compounds form hydrotrioxides in the atmosphere and estimate their lifetime to range from minutes to hours. This makes them stable enough to react with many other atmospheric compounds.
Absorbed in aerosols
The research team also strongly suspects that trioxides can get into tiny airborne particles, known as aerosol sprayswhich represent a health hazard and can cause respiratory and cardiovascular diseases.
While aerosols also have an impact on climate, they are one of the hardest things to describe in climate models. And according to the researchers, there is a high probability that hydrotrioxides affect the amount of aerosols that are produced.
And because aerosols reflect and absorb sunlight, they affect Earth’s heat budget, that is, the proportion of sunlight that Earth absorbs and returns to space, the researchers say.
And when aerosols absorb substances, they grow and contribute to the formation of clouds, which also affects the temperature of the Earth and the climate in general, they add.
The researchers hope that the discovery of hydrotrioxides will help us learn more about the effect of the chemicals we emit, although they are not worried about the finding.
They believe this discovery suggests that there could be many other things in the air that we don’t yet know about. In fact, the air around us is a huge tangle of complex chemical reactions.
Xavier QuerolResearch Professor at the CSIC at the Institute for Environmental Diagnosis and Water Studies (IDAEA0), who did not participate in this study, points out that trioxides and other oxidizing radicals are types of compound that, precisely because they are so reactive, last very little time in the atmosphere, in some cases only fractions of a second.
That is why the formation of trioxides had not been demonstrated until now, although it was suggested that it could occur. Having detected them will help to understand aspects of the formation of tropospheric ozone and secondary aerosols that we do not understand well. But we still don’t know the quantitative implications for climate or air quality. It will be important to clarify it, concludes Querol.
Hydrotrioxide (ROOOH) formation in the atmosphere. Torsten Berndt et al. SCIENCE, 26 May 2022, Vol 376, Issue 6596; pp. 979-982. DOI: 10.1126/science.abn6012