The location of the large mystery source of restricted ozone depleting substance revealed

Researchers from the University of Bristol have found significant ongoing emissions of a potent ozone-depleting substance from eastern China.

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.
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.

Carbon tetrachloride (CCl4) was historically used as a solvent, cleaning agent, and as a feedstock in the production of other compounds such as the chlorofluorocarbons. Though CCl4 production and consumption for dispersive applications have been banned under the Montreal Protocol since 2010, it continues to be produced for certain permitted exemptions and for nondispersive feedstock applications.

In a new study, collaborators from South Korea, Switzerland, Australia, and the USA, researchers at the University of Bristol have quantified a site in East Asia to identify the magnitude and location of emissions from this region. For 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.

Scientists discovered that there are significant ongoing emissions from eastern China and that these account for a large part of the missing emissions from global estimates.

Truth be told, emanations from specific regions may have expanded marginally since 2010. The outcomes from the investigation demonstrate the development of another source of emissions from the Shandong province of China after 2012.

While the aftereffects of this and prior investigations in Europe and the USA currently clarify a vast piece of the worldwide appropriation of carbon tetrachloride emissions, there are still expansive holes in our knowledge. Besides, late reports have recommended that a lot of this gas might be discharged accidentally amid the generation of different chemicals, for example, chlorine.

Lead author, Dr. Mark Lunt, from the University of Bristol’s School of Chemistry, said: “Our results show that emissions of carbon tetrachloride from the eastern Asia region account for a large proportion of global emissions and are significantly larger than some previous studies have suggested.

“Not only that but despite the phase-out of carbon tetrachloride production for emissive use in 2010, we found no evidence for a subsequent decrease in emissions.”

Dr Matt Rigby, Reader in Atmospheric Chemistry at the University of Bristol and co-author, said: “Our work shows the location of carbon tetrachloride emissions. However, we don’t yet know the processes or industries that are responsible. This is important because we don’t know if it is being produced intentionally or inadvertently.

“There are areas of the world such as India, South America and other parts of Asia, where emissions of ozone-depleting gases may be ongoing, but detailed atmospheric measurements are lacking.”

Lead author, Dr. Mark Lunt, from the University of Bristol’s School of Chemistry, said: “Our results show that emissions of carbon tetrachloride from the eastern Asia region account for a large proportion of global emissions and are significantly larger than some previous studies have suggested.

“Not only that but despite the phase-out of carbon tetrachloride production for emissive use in 2010, we found no evidence for a subsequent decrease in emissions.”

“Studies such as this show the importance of continued monitoring of ozone-depleting gases. There is a temptation to see ozone depletion as a problem that has been solved. But the monitoring of man-made ozone-depleting gases in the atmosphere is essential to ensure the continued success of the phase-out of these compounds.”

The study is published in the journal Geophysical Research Letters.