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Location of source of banned ozone-depleting chemical located

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More evidence from the University of Bristol identifies Eastern China as the source of increased levels of the ozone-depleting emissions of carbon tetrachloride, a compound banned in 2010, reported Digital Journal (Canada).

In May 2018, a group of scientists raised a red flag, warning that an unexpected and persistent increase in ozone-destroying chemicals, called chlorofluorocarbons (CFCs) had been documented.
In the May 2018 study, led by researchers with the U.S. National Oceanic and Atmospheric Administration with help from scientists in the Netherlands and the United Kingdom, it was determined the likely rise in CFCs was due to unreported production, something that was banned under the 1987 Montreal Protocol.

As a result of the Montreal Protocol, the world agreed to end the production of CFC-11 compounds, commonly used as refrigerants, aerosol sprays, and in old Styrofoam altogether by 2010.

University of Bristol study
However, according to a new study that further compliments the May 2018 study, researchers have found that global emissions have not decreased as was expected.

It was expected that production of CFCs should by now be close to 0. However, the slower than expected rate of decline of carbon tetrachloride in the atmosphere shows this is not the case, with about 40,000 tons still being emitted each year.

The exact source of the emissions was believed to be coming from Eastern Asia. With collaboration from South Korea, Switzerland, Australia, and the USA, researchers at the University of Bristol aimed to quantify emissions from eastern Asia. Their results were published in the journal Geophysical Research Letters in September 2018.

The results of the study show around half of the "missing" global emissions of carbon tetrachloride originated from eastern China between 2009 and 2016, according to researchers.

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," he added, "but despite the phase-out of carbon tetrachloride production for emissive use in 2010, we found no evidence for a subsequent decrease in emissions." And there is evidence of a new source of emissions coming from China's Shandong province after 2012. There is also the possibility that Carbon tetrachloride is being inadvertently released in the production of other chemicals, like chlorine gas.

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."

He also added: "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."

It may be that we have become complacent, thinking the problem with ozone-depleting gases has been solved, but this study tells us we need to continually monitor our atmosphere to ensure the phase-out of these chemicals, says Dr. Lunt.

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