Massive Australian Wildfires Damaged Ozone Layer: Study

Researchers say the massive pillars of smoke above the huge wildfires in Australia in late 2019 and early 2020 – what’s called the Black Summer – injected over 1 million tons of smoke particles as high as 35 km into the atmosphere and caused chemical reactions that set back the recovery of stratospheric ozone by about 10 years, Tom Metcalfe reported for Chemistry World.

Photo Insert: The Orroral Valley Fire as seen from Tuggeranong

“This event essentially canceled out a decade’s worth of recovery,” says atmospheric chemist Susan Solomon of the Massachusetts Institute of Technology (MIT) and the lead author of the study. “It only lasted six to eight months, but what if they happen more often?”

The Australian wildfires in the southern summer of 2019 and 2020 were some of the worst on record. It’s estimated that they burned more than 240,000 sq km of bush over six months and resulted in more than 400 deaths, while their towering clouds of smoke – called pyrocumulonimbus – measured more than 1,000 km across and stayed intact for several months.

Solomon and her colleagues observed the chemical effects of the smoke clouds on the stratosphere in mid-latitudes in data from three orbiting scientific instruments.

Each showed the smoke particles caused a sharp drop in the amount of nitrogen dioxide in the stratosphere – a cold and very dry layer of the upper atmosphere, typically between 10 km and 50 km above the Earth’s surface – which is the first step of a chemical cascade that results in ozone depletion.

Solomon likens the effect of smoke particles to the ash particles in volcanic plumes, which gather moisture on their surfaces that then react with other chemicals circulating in the stratosphere, including dinitrogen pentoxide, to form nitric acid.

Under normal conditions, dinitrogen pentoxide in the stratosphere helps keep chlorine-based chemicals in check, with photochemical reactions resulting in other nitrogen compounds, including nitrogen dioxide, that bind to them.

But when the particles from volcanic plumes – or the particles from wildfire smoke – convert dinitrogen pentoxide into nitric acid, a reduction in nitrogen dioxide is observed and any excess chlorine compounds morph into ozone-destroying chlorine monoxide.

WEEKLY FEATURE : MVP Group Keeps Lights On During Pandemic