Mysterious Source of Banned Ozone Depleting Substance Uncovered

Substances such as carbon tetrachloride are responsible for destroying ozone high up in the atmosphere. The ozone layer prevents harmful ultraviolet radiation from reaching the Earth’s surface.  (Image: via University of Bristol)
Substances such as carbon tetrachloride are responsible for destroying ozone high up in the atmosphere. The ozone layer prevents harmful ultraviolet radiation from reaching the Earth’s surface. (Image: via University of Bristol)

Researchers from the University of Bristol have found significant ongoing emissions of a potent ozone-depleting substance from eastern China. The compound, carbon tetrachloride, contributes to the destruction of the Earth’s ozone layer, which protects us from harmful ultraviolet radiation.

As a result, the production of carbon tetrachloride has been banned throughout the world since 2010 for uses that will result in its release to the atmosphere. However, recent studies have shown that global emissions have not declined as expected, with about 40,000 tonnes still being emitted each year.

The origin of these emissions has puzzled researchers for many years. Alongside collaborators from South Korea, Switzerland, Australia, and the U.S., researchers at the University of Bristol aimed to quantify emissions from eastern Asia.

To do this, they used ground-based and airborne atmospheric concentration data from near the Korean peninsula and two models that simulate the transport of gases through the atmosphere.

Their results, published in the journal Geophysical Research Letters, show that around half of the “missing” global emissions of carbon tetrachloride originated from eastern China between 2009 and 2016. Lead author, Dr. Mark Lunt, from the University of Bristol’s School of Chemistry, said:

In fact, emissions from certain regions may have increased slightly since 2010. The results from the study show the emergence of a new source of emissions from China’s Shandong Province after 2012. While the results of this and earlier studies in Europe and the U.S. now explain a large part of the global distribution of carbon tetrachloride emissions, there are still large gaps in our knowledge.

Furthermore, recent reports have suggested that very large amounts of this gas may be emitted inadvertently during the production of other chemicals, such as chlorine. Dr. Matt Rigby, Reader in Atmospheric Chemistry at the University of Bristol and co-author, said:

It is hoped that this work can now be used by scientists and regulators to identify the cause of these emissions from eastern Asia. Ultimately, if these emissions can be avoided, it would hasten the recovery of the stratospheric ozone layer. Dr. Lunt said:

 Provided by: University of Bristol [Note: Materials may be edited for content and length.]

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