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Threat to ozone layer as four new ozone-eating gases found

Tue, 03/11/2014 - 10:08am
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Four new harmful fluorinated gases, of the type that destroys Earth’s protective ozone layer, have been found in the atmosphere. Three of the gases are CFCs — chlorofluorocarbons — whose use has been progressively banned since the 1990s under the United Nations Montreal Protocol which aims to protect the ozone layer.

According to new research from the University of East Anglia (UEA) in the UK, more than 74,000 tonnes of three new CFCs and one new hydrochlorofluorocarbon (HCFC) have been released into the atmosphere. HCFCs, too, are now the subject of regulatory controls with many countries, including the United States, committed to a phasing down of HCFC use.

CFCs and HCFCs pose a danger to life on Earth as they cause holes to form in the ozone layer in the atmosphere above Earth’s north and south poles. The ozone layer is present at an altitude of between 20 and 50 kilometers (about 12 and 30 miles) and absorbs ultraviolet radiation emitted by the sun, known to cause skin cancer and eye cataracts.

The research team analysed unpolluted air collected in Tasmania between 1978 and 2012 as well as core samples of polar firn snow taken from Greenland. Firn snow, sometimes known as névé, is old snow lying on top of glaciers, granular and compacted, but which hasn’t yet been converted into ice. It provides a century-old natural archive of what has happened in Earth’s atmosphere.

The UEA analysis showed that all four new gases had been released into the atmosphere recently. The researchers found significant accumulations of two of the new gases on a scale not seen for any other CFCs since international controls on their use were introduced late last century. Although the accumulations discovered were significant, they fall well short of peak CFC emissions during the 1980s when about a million tonnes of these harmful gases were being pumped into the atmosphere each year.

Lead researcher Dr Johannes Laube from UEA’s School of Environmental Sciences commented, “Our research has shown four gases that were not around in the atmosphere at all until the 1960s which suggests they are man-made.”

Explaining the background, Laube said, “CFCs are the main cause of the hole in the ozone layer over Antarctica. Laws to reduce and phase out CFCs came into force in 1989, followed by a total ban in 2010. This has resulted in successfully reducing the production of many of these compounds on a global scale. However, legislation loopholes still allow some usage for exempted purposes.”

The four new gases found are CFC-112, CFC112a, CFC-113a and HCFC-133a. Stressing how these continuing emissions will contribute to the destruction of the ozone layer, Laube called for further investigations to trace the source of the new gases discovered, adding, “We don’t know where the new gases are being emitted from and this should be investigated. Possible sources include feedstock chemicals for insecticide production and solvents for cleaning electronic components.”

According to BBC News, CFC-113a has been listed as an "agrochemical intermediate for the manufacture of pyrethroids", a type of insecticide once widely used in agriculture. CFC-113a, along with HCFC-133a, is also used in the production of refrigerants. Both CFC-112 and 112a may have featured in the production of solvents used to clean electrical components.

CFCs can take years to break down in the atmosphere so even if all emissions were to stop immediately, as Laube pointed out, “They will still be around for many decades to come.”

The UEA research, entitled, ‘Newly detected ozone depleting substances in the atmosphere’ was published in the journal Nature Geoscience on Sunday, March 9, 2014.

Sources:

University of East Anglia

US Environmental Protection Agency

BBC News

Montreal Protocol

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