(ORDO NEWS) — Organic matter raised high into the stratosphere by fires allows aggressive chloride ions to appear even at moderate temperatures.
This leads to the formation of “ozone holes” far beyond the Antarctic, where they form most often.
Large-scale fires that occurred in Australia in the summer of 2019-2020 led to damage to the Earth‘s ozone layer.
This is the conditional name for the region of the stratosphere at an altitude of several tens of kilometers, where molecules consisting of three oxygen atoms accumulate – ozone.
It serves as a natural shield for the planet’s surface from the harsh solar ultraviolet.
During the Australian fires in 2019-2020, about a million tons of smoke and soot fell into the stratosphere. Chemical transformations began in it, which scientists had not encountered before.
They led to an increase in the content of chlorine nitrate in the atmosphere and a weakening of the ozone layer. Scientists from the Massachusetts Institute of Technology (MIT) figured out exactly how this happened.
The main danger to the ozone layer is chloride ions, which destroy ozone molecules. In the atmosphere, such ions appear from hydrochloric acid, which, in turn, can be formed from chlorofluorocarbons.
Volatile chlorofluorocarbons (including freon and freon) were widely used as refrigerants – solvents – in aerosols.
To protect the ozone layer, their production has been discontinued, but some of these persistent substances remain in the atmosphere.
To find out exactly what happened to all these compounds under the influence of the smoke from the Australian fires, Kane Stone (Kane Stone) and his colleagues used satellite observations.
Previously, such work has shown that soot reduces the number of active nitrogen molecules that protect the ozone layer. Now it turned out that it also accelerates the appearance of aggressive chlorine ions.
In the stratosphere, hydrochloric acid and other chlorine-containing compounds must interact with water in order for destructive ions to appear.
Such interaction requires very low temperatures, which is why “ozone holes” most often appear over Antarctica and the Arctic.
However, in the presence of organic substances, the acid can interact with them, and at much higher temperatures.
This is what happened in 2019-2020, when ozone depletion was observed not only over Antarctica, but also at lower latitudes, in Australia itself.
Hydrochloric acid and other chlorine compounds absorbed on organic particles under the action of ultraviolet light release aggressive ions, which destroy ozone.
As a result, after the fires of 2019-2020 over Australia, the ozone layer has weakened by 3-5%.
This is not such a small indicator: for comparison, let’s say that after the adoption of the Montreal Protocol and the ban on the production of chlorofluorocarbons, the ozone layer is restored at an average rate of one percent per decade.
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