Wildfire's are Destroying the Earth's Ozone Layer

 Figure 1: Australian wildfire results in towering clouds of smoke entering the stratosphere

Drought conditions result in low moisture in vegetation. The amount of moisture in vegetation determines how easily it ignites when exposed to heat. With low moisture, the vegetation becomes more flammable because the heat does not have to remove as much water to generate combustion, which is the series of chemical reactions that produce fire. More and more areas across the globe have an increased risk of wildfires as droughts intensify due to climate change. Wildfires naturally deplete the Earth’s ozone layer due to smoke entering the stratosphere. 

Figure 2: Air Composition in the atmosphere 

Clouds of smoke being sent into the Earth’s stratosphere by wildfires eat away at the ozone layer through a potent mix of smoke, atmospheric chemistry, and ultraviolet light. Following the 2020 wildfire in Australia, satellite data revealed that the smoke was reacting to the atmospheric molecules to eat away Earth’s ozone layer. The atmosphere is mainly comprised of nitrogen and oxygen along with a small percentage of other compounds. 

Once the smoker particles enter the stratosphere, they react with stratospheric gases along with emissions of ozone-destroying chemicals. This combined with solar radiation creates chlorine radicals, a type of chemical known for attacking the ozone layer called chlorofluorocarbons. 

 

Figure 2: Chlorofluorocarbon molecule 

This mass reaction in 2020 was responsible for depleting about 3-5% of the ozone layer in parts of the Southern Hemisphere. While this is a small percentage, it rivals the scale of the impact human emissions have on creating chlorofluorocarbons in the stratosphere. Chlorofluorocarbons were used in refrigerators and air conditioners, but their emissions to the atmosphere led to a large hole in the ozone layer over Antarctica which limits how much of the sun’s ultraviolet radiation reaches the planet’s surface. After the 2020 wildfire in Australia, satellites also caught hydrogen chloride gas, and chlorine nitrate, as well as others. There was a tremendous drop in hydrogen chloride, caused by the breakdown of chlorofluorocarbons which linger in the stratosphere for decades. At low temperatures, hydrogen chloride gas can dissolve into icy clouds, which is essential to starting the chain of reactions that form ozone-depleting chemicals.    

Organic particles in the smoke from wildfires can absorb hydrogen chloride gas even at warmer temperatures, starting that essential step. The smoke particles act as a catalyst, helping speed along other reactions in the atmosphere. The smoke particles speed up the transformation of other chlorine-containing gases, such as chlorine nitrate and hypochlorous acid into chlorine compounds that are highly reactive to sunlight. Mixing the sun’s ultraviolet radiation with new chlorine compounds produces chlorine radicals; molecules that are extremely chemically reactive, and attack ozone molecules. 

The discovery of this wildfire-related process for destroying the ozone is a very worrisome setback to the recovery of the ozone layer. Climate change is expected to increase the intensity and frequency of wildfires around the globe, sending more smoke clouds into the stratosphere. However, the discovery of the organic particles in the stratosphere can improve our understanding of what controls the production of an ozone hole and the necessary steps that need to be taken to prevent them. 

References 

Gramling, C. (2023, March 9). How wildfires deplete the Earth's ozone layer. Science News. Retrieved March 13, 2023, from https://www.sciencenews.org/article/wildfire-ozone-layer-chemical-reaction-smoke

Moore, A. (2022, August 29). Climate change is making wildfires worse - here's how. College of Natural Resources News. Retrieved March 13, 2023, from https://cnr.ncsu.edu/news/2022/08/climate-change-wildfires-explained/#:~:text=With%20low%20moisture%2C%20vegetation%20becomes,wildfire%20risk%20as%20droughts%20intensify. a