Mysterious source of ozone-depleting chemical baffles NASA

Aug 20, 2014
Satellites observed the largest ozone hole over Antarctica in 2006. Purple and blue represent areas of low ozone concentrations in the atmosphere; yellow and red are areas of higher concentrations. Credit: NASA

A chemical used in dry cleaning and fire extinguishers may have been phased out in recent years but NASA said Wednesday that carbon tetrachloride (CCl4) is still being spewed into the atmosphere from an unknown source.

The world agreed to stop using CC14 as part of the Vienna Convention on Protection of the Ozone Layer and its Montreal Protocol, which attained universal ratification in 2009.

"Parties to the Montreal Protocol reported zero new CCl4 between 2007-2012," the US space agency said in a statement.

"However, the new research shows worldwide emissions of CCl4 average 39 kilotons per year, approximately 30 percent of peak emissions prior to the international treaty going into effect."

CC14 levels are not enough to reverse the decreasing trend of ozone-depletion, but experts are still mystified as to where it is coming from.

With no new reported emissions, atmospheric concentrations of the compound should have declined at an expected rate of four percent per year since 2007.

However, observations from the ground showed were only declining one percent per year.

"We are not supposed to be seeing this at all," said Qing Liang, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

"It is now apparent there are either unidentified industrial leakages, large emissions from contaminated sites, or unknown CCl4 sources."

This video is not supported by your browser at this time.
This NASA video discusses new research that shows Earth's atmosphere contains an unexpectedly large amount of an ozone-depleting compound from an unknown source decades after the compound was banned worldwide. Credit: NASA

Researchers used NASA's 3-D GEOS Chemistry Climate Model and data from global networks of ground-based observations to establish the first estimate of average global CC14 emissions from 2000 to 2012.

In going through the data, researchers also learned that the chemical stays in the atmosphere were 40 percent longer than previously thought.

"People believe the emissions of ozone-depleting substances have stopped because of the Montreal Protocol," said Paul Newman, chief scientist for atmospheres at NASA.

"Unfortunately, there is still a major source of CCl4 out in the world."

The study was published in the journal Geophysical Research Letters.

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User comments : 17

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supamark23
4.6 / 5 (12) Aug 20, 2014
Almost certainly one or more developing countries are still using the stuff and not reporting it. Their gov't may not even know about it - regulations and oversight tend to be nonexistant in much of the developing world.
SHREEKANT
1.2 / 5 (9) Aug 20, 2014
"NASA said Wednesday that carbon tetrachloride (CCl4) is still being spewed into the atmosphere from an unknown source."

MY VIEW: CCl4 is one of the cold loving compound so its source is COLD PLACES like poles. It is also interesting that it will not cross about 100 km height [just above mesosphere].
geaux_bleu
4.8 / 5 (8) Aug 20, 2014
Cold loving compound? I'm not familiar with that scientific term. Carbon tet is a non-polar substance, which means it's soluble in non-polar substances like heptane or xylene. In that sense, it is 'non-polar' loving.
DJ311
2 / 5 (3) Aug 20, 2014
It might be possible for chlorine released from water purification to react with methane in the atmosphere in the present of UV to create carbon tetrachloride. A chemist would need verify if this type of process could occur.
Gaby_64
4 / 5 (4) Aug 21, 2014
why dont they point their spectroscope satellites they intend to use to determine planet atmosphere composition of far away planets at our planet to determine the source area?

using a few together should allow for accurate measurement of volumes of space
im surprised we dont already do that to map air composition for better weather prediction.
and also calculating our actual air sustainability, although i suspect it would be so shocking they would try and hide it.
axemaster
5 / 5 (3) Aug 21, 2014
The reason these compounds appear to be concentrated in destroying ozone near the poles is that a special type of high-altitude cloud forms at the poles (I forget the name). Basically, ice crystals in these clouds collect the destructive catalytic molecules and then serve as reaction sites, greatly enhancing the rate of ozone destruction. These clouds tend to form during the polar winters, which is why the depletion is most intense at those times.

It is most likely that these molecules are not actually concentrated at the poles - they are probably distributed pretty evenly around the globe. But the clouds at the poles are where the damage occurs.
daggaz
5 / 5 (1) Aug 21, 2014
DJ311: Chlorine in water purification dissolves into acids, which do their reactivity, quickly pass the chlorine ion further down the reaction chain into increasingly stable molecules. This drives the equilibrium far away from spontaneous volatisation of chlorine gas back out of the water. The extremely low atmospheric chlorine concentration then combines with the fact that each methane molecule needs to undergo the UV-assisted chlorination reaction a total of four times, with each step becoming increasingly unlikely. This means that the chlorination of atmospheric methane by UV is very unlikely to be the source of such a significant amount of gas. Developing countries are indeed the most likely culprits, though a UV assisted regenerative process in the upper atmosphere might be responsible for the greater observed stability of the molecule.
TheGhostofOtto1923
4.2 / 5 (5) Aug 21, 2014
Well obviously it's the Chinese.

"In the United States and Canada in the late 19th and early 20th century, the occupation of laundry worker was heavily identified with Chinese Americans. Discrimination, lack of English-language skills, and lack of capital kept Chinese Americans out of most desirable careers. Around 1900, one in four ethnic Chinese men in the U.S. worked in a laundry, typically working 10 to 16 hours a day."

-They know from experience what the best dry cleaning solvents are. And they are very tradition-bound. And they don't mind the heat. And they think endangered animal parts confer special powers. These all add up.
antigoracle
1 / 5 (3) Aug 21, 2014
adam_russell_9615
not rated yet Aug 21, 2014
Couldnt the source be detected by satellite?
socean
not rated yet Aug 23, 2014
Another job, perhaps, for Google's Loon Balloon network? Monitoring the atmosphere.
Whydening Gyre
not rated yet Aug 23, 2014
Couldnt the source be detected by satellite?

ya mean, like this one?
http://phys.org/n...tml#nRlv
baudrunner
not rated yet Aug 24, 2014
Carbon Tetrachloride is still used in industrial applications, such as in defatting animal glands for processing in the pharmaceutical industry. Carbon tetrachloride has been identified in a third of US hazardous waste sites. And I am wondering - admitting ignorance here - if it is possible that CCl4 is a byproduct of the manufacture of nitrate fertilizers using the original method, which is about 250 years old. That would explain the quantities measured. Anybody know?
Raygunner
5 / 5 (2) Aug 24, 2014
The reason these compounds appear to be concentrated in destroying ozone near the poles is that a special type of high-altitude cloud forms at the poles (I forget the name). Basically, ice crystals in these clouds collect the destructive catalytic molecules and then serve as reaction sites, greatly enhancing the rate of ozone destruction. These clouds tend to form during the polar winters, which is why the depletion is most intense at those times.

It is most likely that these molecules are not actually concentrated at the poles - they are probably distributed pretty evenly around the globe. But the clouds at the poles are where the damage occurs.


The clouds you mention are polar stratospheric clouds, also known as nacreous clouds.
Whydening Gyre
3 / 5 (2) Aug 24, 2014
Carbon Tetrachloride is still used in industrial applications, such as in defatting animal glands for processing in the pharmaceutical industry. Carbon tetrachloride has been identified in a third of US hazardous waste sites. And I am wondering - admitting ignorance here - if it is possible that CCl4 is a byproduct of the manufacture of nitrate fertilizers using the original method, which is about 250 years old. That would explain the quantities measured. Anybody know?

I don't. But I think it's a pretty good question - that would predicate a little research. Try googling some of your terms...
baudrunner
not rated yet Aug 25, 2014
summary: Chemists have now found an interesting new approach that may lead to effective recycling of CCl4, an unwanted byproduct of chlorinated hydrocarbon production.

http://www.scienc...4935.htm

Couldn't find any direct data related to chemical fertilizers, but I do recall seeing Cl involved in a Fessenden & Fessenden text of organic chemistry years ago in which the content was related.

SHREEKANT
not rated yet Aug 27, 2014
please refer my comment dated 20th Aug.'2014 in which i had given a short hint "CCl4 is one of the cold loving compound so its source is COLD PLACES like poles"

please refer to [24th, Aug'2014]

http://www.nature...20140826