. Copper released into the environment by fungicides brake pads, antifouling sprays on boats, and other sources, may contribute significantly to stratospheric levels of ozone depletion.
In a paper appearing this week in the journal Nature Communications, UC Berkeley geochemists show that copper in soil and seawater acts as a catalyst to turn organic matter into both methyl bromide and methyl chloride, two potent halocarbon compounds that destroy ozone. Sunlight worsens the situation, boosting production of these methyl halides by a factor of 10.
The findings provide some answers to a long-standing mystery regarding the origins of a lot of the methyl bromide or methyl chloride found in the stratosphere. These methyl halides are now the dominant source of ozone-depleting chlorine and bromine in the stratosphere, following the global ban on chlorofluorocarbon refrigerants (CFCs) and brominated halons for fire extinguishers that start in 1989,. The role of methyl halidides is increasing as the long-lasting CFCs and halons gradually disappear from the atmosphere.
” If we don’t know the origin of methyl bromide or methyl chloride, how can we ensure that they are reduced with CFCs? Robert Rhew (UC Berkeley professor of geography, environmental science policy, and management), was the paper’s senior writer. “By 2050,, we should be back at relatively normal levels of ozone. However, things such as the continuing emissions of methyl bromide or methyl chloride can cause delays in our road to recovery. The environment’s copper usage is expected to rise rapidly over the next few years. This should be taken into account when forecasting future halogen loads and ozone recovery. “
Earth’s ozone layer protects us from sun-induced cancer. However, chemicals containing bromine and chlorine — such as CFCs or halons — were discovered in the 1980s. They destroyed the ozone and created thinner layers in the stratosphere, which allowed in more radiation. The ozone layer, despite a ban on the production of CFCs or halons, which are the main sources of halogens in the atmosphere, has not been repaired. Rhew stated that last year’s hole in the ozone layer over Antarctica was as severe as ever.
The persistence of the ozone gap is due, in large part, to the persistence and dissipation of banned ozone depleting compounds that take decades to evaporate in the stratosphere. However, some ozone-depleting chemical are still being released. Some replacements for banned refrigerants come under scrutiny.
The two main contributors to the current crisis are methyl chloride (MHC) and methyl bromide (MBR). one atom of bromine is more destructive than one atom of chlorine.
Melody bromide has been banned from being used in agricultural soil fumigants, but it can still be used to control pests and prevent the shipping of agricultural products. Even though most of the methyl chloride’s emissions are from natural or biomass burning, methyl chloride is still used as a chemical feedstock. But the total amount of these methyl halides produced each year still do not add up to the observed yearly addition of these chemicals to the atmosphere, a fact that has puzzled scientists for more than 20 years.
Rhew stated that about one-third of the atmospheric methyl bromide or methyl chloride comes from unknown sources. Rhew stated that copper may be an important source for the missing methyl bromide or methyl chloride.
” We have banned methyl bromide. But are there other environmental changes that can cause large amounts of this compound to enter the atmosphere? Rhew stated that copper-catalyzed copper production has been increasing in popularity.
First author and former UC Berkeley doctoral student Yi Jiao, now a postdoctoral fellow at the University of Copenhagen in Denmark, noted that copper compounds are allowed on organic crops, a legacy of its use in farming since the 1700s, including as a major antifungal agent in the Bourdeax mixture used since the 1880s in France to prevent downy mildew on grapes. Because of its history, copper contamination of soils is a significant problem in Europe today. According to the authors, another reason for concern is the ozone-depleting potential of copper.
” Please note that organic agriculture does not contribute to ozone depletion. Jiao tweeted this week that copper-based fungicides may have adverse effects on the atmosphere, which might be worth considering in terms of their overall environmental impact. “With widespread use of copper in the environment, this potentiall