According to NASA research, "Earth's atmosphere contains an unexpectedly large amount of an ozone-depleting compound from an unknown source decades after the compound was banned worldwide" (http://go.nasa.gov/1kVAWI0).
What can we discuss about ozone depletion? Is there any unknown major emission source of CCl4 from the nature? or What could be unknown physicochemical processes in case the major source of CCl4 is man-made emission?
http://go.nasa.gov/1kVAWI0
CCL4 = carbon tetrachloride
The following are the known natural sources of CCL4 emission
1. Volcanoes (but in extremely trace amounts - order 1 part per billion) - according to Schwander etal 2004 Journal of Geophysical Research - world wide emissions would be about 3 +/- 1 tonnes per year (insignificant)
2. Mine gas and mineral leakage (I don't believe anyone is detecting CCL4 emission associated with increases in fracking tho this might not be checked for)
3. The arctic ocean (and ocean bottom) - warming may accelerate release of these stored deposits.
4. Some forms of marine algae emit CCL4
5. There is an atmospheric chemistry process that involves Chlorine and Methane that can make CCL4 (at very low rates)
So its possilble that the now observed excess is due to a combination of these natural sources. Personally I doubt this.
I believe the most likely culprit are the following two "black market" sources:
a) insecticide production
b) solvents for various electronic components
Prior to the Montreal Protocol, the biggest source of CCL4 emission was the dry cleaning industry.
CCL4 = carbon tetrachloride
The following are the known natural sources of CCL4 emission
1. Volcanoes (but in extremely trace amounts - order 1 part per billion) - according to Schwander etal 2004 Journal of Geophysical Research - world wide emissions would be about 3 +/- 1 tonnes per year (insignificant)
2. Mine gas and mineral leakage (I don't believe anyone is detecting CCL4 emission associated with increases in fracking tho this might not be checked for)
3. The arctic ocean (and ocean bottom) - warming may accelerate release of these stored deposits.
4. Some forms of marine algae emit CCL4
5. There is an atmospheric chemistry process that involves Chlorine and Methane that can make CCL4 (at very low rates)
So its possilble that the now observed excess is due to a combination of these natural sources. Personally I doubt this.
I believe the most likely culprit are the following two "black market" sources:
a) insecticide production
b) solvents for various electronic components
Prior to the Montreal Protocol, the biggest source of CCL4 emission was the dry cleaning industry.
Besides, the research shows that N2O contributes substantially to ozone layer depletion. Accordingly to NOAA, N2O is now the largest man-made ODS and is expected to remain the largest throughout the 21st century. See more detail at (http://rstb.royalsocietypublishing.org/content/367/1593/1256.full.pdf.
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