It has been known, since the 70s, that CFCs (Chlorofluorocarbons) gases are the main responsible for the destruction of the ozone layer. The reactions that occur and how ozone is degraded by these substances are well explained in the text Ozone layer. Therefore, since 2010, the emission of these substances is strictly prohibited.
However, a recent news, published in the magazine Nature Geoscience, of March 9, 2014, brought a very bad alert: four new gases that deplete the ozone layer have been discovered. Three of them are CFCs, which are: CFC-112, CFC-112a, CFC-113a, and the fourth gas discovered is an HCFC (hydrochlorofluorocarbons), which is the HCFC-133a. The structure of these compounds is shown below:
CFC-112CFC-112a
(1,1,2,2-tetrachloro-1,2-difluorethane) (1,1,2,2-tetrachloro-2,2-difluorethane)
Cℓ F F Cℓ
| | | |
Cℓ ─ C C Cℓ Cℓ ─ C ─ C ─ Cℓ
| | | |
F Cℓ F Cℓ
CFC-113aHCFC-133a
(1,1,1-trichloro-2,2,2-trifluoroethane) (1,1,1-Trifluoro-2-chloroethane)
F Cℓ F H
| | | |
F C ─ C C F ─ C ─ C ─ H
| | | |
F Cℓ F Cℓ
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These substances are considered new because, although we already know that CFCs degrade the ozone layer, these discovered gases were not among the CFCs indicated as being present in the atmosphere. Until now, it was already known that seven other types of CFCs and six types of HCFCs contributed to the depletion of stratospheric ozone. They are among those prohibited by the Montreal Protocol — an agreement signed in 1987 by 150 countries to eliminate the production of these gases harmful to the ozone layer. But analyzes made by scientists at the University of East Anglia, London, UK, have shown the presence of these four new gases in the atmosphere since the mid-1960s.
Which means they weren't present there before, meaning they come from some human activity. Two of them are accumulating very fast in the atmosphere, mainly CFC-113a gas.
But how did they manage to make that determination?
Well, simply put, the team led by atmospheric scientist Johannes Laube collected air samples that were trapped in blocks of snow. These samples are sort of “natural archives”, as they can remain there for up to a decade. The analyzed air portions were extracted from the snow of Greenland in 2008 and the unpolluted air of the Cape Grim, an island region of Tasmania, Australia, between 1978 and 2012. Among the analysis, detection and quantification techniques that were used were the gas chromatography with mass spectrometry detector.
The results showed estimates that since before 2012 the emissions of all four of these new gases that deplete the ozone layer combined reached more than 74 thousand tons.
Scientists recognize that this is a much lower figure than what was released in the 1980s of the other CFC gases. But this concentration is increasing and gradually destroying the layer of ozone. Each chlorine atom released by CFCs can, on average, destroy about a million molecules of ozone. The worst thing is that these gases are not quickly eliminated from the atmosphere, but remain for decades and even centuries. So even if they stop being issued, its effect will contribute to raising the hole in the ozone layer for many decades.
Some possible sources are chemical inputs for the production of insecticides and solvents such as cleaning materials for electronic components. But more detailed investigations and research will provide more data on these sources.
This shows how important it is to continue studying and monitoring our Earth's atmosphere.
By Jennifer Fogaça
Graduated in Chemistry
Would you like to reference this text in a school or academic work? Look:
FOGAÇA, Jennifer Rocha Vargas. "Four New Gases That Deplete the Ozone Layer"; Brazil School. Available in: https://brasilescola.uol.com.br/quimica/quatro-novos-gases-que-destroem-camada-ozonio.htm. Accessed on July 27, 2021.
