How smoke from Australia’s megafires ate away at the ozone

The smoke from the wildfires that raged in southeastern Australia in 2019 and 2020 was known to have destroyed the Earth’s ozone layer, but exactly how it was not clear. An analysis of the chemical reaction shows that the smoke may have caused the hydrochloric acid to dissolve at high temperatures, producing more reactive chlorine molecules that destroy the ozone.

Between November 2019 and January 2020, the Black Summer wildfires released nearly one million tons of smoke into the atmosphere.

Kane Stone of the Massachusetts Institute of Technology said, “Satellite observations showed a chemistry that had never been seen before. Of particular concern were the decrease in hydrochloric acid and the increase in chlorine nitrate, and the harmful UV rays. can deplete the thin layer of ozone molecules that block the

Stone and his colleagues suspected that the changes were caused by the way wildfire smoke affects the solubility of hydrochloric acid in the stratosphere.

Hydrochloric acid can normally only be dissolved at the very low temperatures that occur at the Earth’s poles. Upon dissolution, it creates chlorine molecules that are more likely to react with water and actively destroy ozone. However, based on laboratory studies, researchers have found that organic particles, like wildfire smoke, can cause hydrochloric acid to dissolve at higher temperatures.

To test this idea, the researchers modeled how changes in the solubility of hydrochloric acid affect stratospheric chemistry. They found that the model matched “very well” observations of the stratosphere during the fires in Australia, Stone says.

Their model suggests that smoke from fires caused a 3-5% depletion of the ozone layer above mid-latitudes, increasing the size of the seasonal ozone hole over Antarctica.

Albert Ansmann of Germany’s Leibniz Tropospheric Institute believes their model explains ozone depletion in mid-latitudes, but thinks smoke could have a more significant effect in Antarctica. Smoke from fires in the Northern Hemisphere can have similar effects on Arctic ozone.

Ansmann said his group has seen an increase in the amount of smoke reaching the stratosphere over the past decade, a problem that could be addressed as a warmer climate leads to larger and more intense wildfires. may persist.