Friday, March 14, 2014

Mysterious new man-made gases pose threat to ozone layer

  • Scientists have identified four new man-made gases that are contributing to the depletion of the ozone layer.
  • Two of the gases are accumulating at a rate that is causing concern among researchers.
  • Worries over the growing ozone hole have seen the production of chlorofluorocarbon (CFC) gases restricted since the mid 1980s.
  • Lying in the atmosphere, between 15 and 30km above the surface of the Earth, the ozone layer plays a critical role in blocking harmful UV rays, which cause cancers in humans and reproductive problems in animals.
  • Scientists from the British Antarctic Survey were the first to discover a huge "hole" in the ozone over Antarctica in 1985.
  • The evidence quickly pointed to CFC gases, which were invented in the 1920s, and were widely used in refrigeration and as aerosol propellants in products like hairsprays and deodorants.
  • Remarkably, global action was rapidly agreed to tackle CFCs and the Montreal Protocol to limit these substances came into being in 1987.
  • A total global ban on production came into force in 2010.
  • Researchers from the University of East Anglia have discovered evidence of four new gases that can destroy ozone and are getting into the atmosphere from as yet unidentified sources.
  • Three of the gases are CFCs and one is a hydrochlorofluorocarbon (HCFC), which can also damage ozone.
  • Research has shown four gases that were not around in the atmosphere at all until the 1960s which suggests they are man-made.
  • The scientists discovered the gases by analysing polar firn, perennial snow pack. 
  • Air extracted from this snow is a natural archive of what was in the atmosphere up to 100 years ago.

Grim discovery
  • The researchers also looked at modern air samples, collected at remote Cape Grim in Tasmania.
  • They estimate that about 74,000 tonnes of these gases have been released into the atmosphere. Two of the gases are accumulating at significant rates.
  • The identification of these four new gases is very worrying as they will contribute to the destruction of the ozone layer.
  • Possible sources include feedstock chemicals for insecticide production and solvents for cleaning electronic components.
  • As per research, the three CFCs are being destroyed very slowly in the atmosphere - so even if emissions were to stop immediately, they will still be around for many decades to come.
  • Other scientists acknowledged that while the current concentrations of these gases are small and they don't present an immediate concern, work would have to be done to identify their origin.
  • As per research,of the four species identified, CFC-113a seems the most worrying as there is a very small but growing emission source somewhere, maybe from agricultural insecticides.

Mysterious gases

  • The four new gases have been identified as CFC-112, CFC112a, CFC-113a, HCFC-133a.
  • 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 and HCFC-133a are intermediaries in the production of widely used refrigerantscu
  • CFC-112 and 112a may have been used in the production of solvents used to clean electrical components

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