China The Suspected Source of Greenhouse Perfluoroalkanes
China is the suspected source of greenhouse gases tetrafluoromethane and hexafluoroethane that have been building up in the atmosphere recently.
The source of the atmospheric buildup of these powerful greenhouse gases, tetrafluoromethane and hexafluoroethane, has been a huge mystery. Now, scientific modelling of data from collected air samples suggest that China’s aluminium industry is a major culprit.
In an effort to pinpoint the sources of those emissions, Jooil Kim at the University of California, San Diego, and his colleagues analysed air samples collected roughly every 2 hours between November 2007 and December 2019 on South Korea’s Jeju Island. Armed with the data, the scientists modelled the weather patterns that transported air across the island during that period, to extrapolate the gases’ origins. The results of the extrapolation suggested that aluminium smelters in China account for a large proportion of the release of these chemicals into the atmosphere. Other producers were likely the semiconductor factories in South Korea and Japan.
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Environmental problems caused by the build up of tetrafluoromethane and hexafluoroethane
Tetrafluoromethane (CF4) and hexafluoroethane (C2F6) are thousands of times more effective than carbon dioxide at warming the atmosphere. They are listed under the United Nations Framework Convention on Climate Change (UNFCCC). With atmospheric lifetimes on the order of thousands to tens of thousands of years, PFC emissions represent a permanent alteration to the global atmosphere on human timescales.
They are emitted mainly from the aluminum and semiconductor industries and are among some of the longest-lived greenhouse gases known.
Though the industry has come a long way in understanding and reducing their emissions over the last few decades, the global emissions of CF4 and C2F6 modeled using atmospheric measurements continue to rise by a significantly larger values than those currently reported by industry and government.
Tetrafluoromethane is a powerful greenhouse gas that contributes to global warming through the greenhouse effect. It is a very stable gas with an atmospheric lifetime of roughly 50,000 years. Its greenhouse warming potential is about 6,500 times that of carbon dioxide.
Although structurally similar to banned chlorofluorocarbons (CFCs), tetrafluoromethane does not deplete the ozone layer because the carbon–fluorine bond is much more stable than the carbon-chlorine bond in CFCs.
Just like with tetrafluoromethane, the high stability of C-F bonds in hexafluorethane causes it to be nearly inert. This makes it an extremely stable greenhouse gas, with an atmospheric lifetime of up to 10,000 years. Its global warming potential is 9200 and its ozone depletion potential is 0.
Reference: Journal of Geophysical Research: Atmospheres Volume 126, Issue 16 Research Article on Emissions of Tetrafluoromethane and Hexafluoroethane From East Asia.