Volcanic Halocarbons: Chlorofluorocarbons (CFCs) in Volcanic Emissions
One of Ian Plimer's misquotes happens to be heavily underpinned by numerous scientific measurements and practical experimentation. Although commonly regarded as not naturally occuring, halocarbons and chlorofluorocarbons (CFCs) do occur naturally and are emitted from volcanoes. This applies to both the environment and the atmosphere. As a consequence, we can expect that volcanic activity has a much higher impact on ozone depletion than previously thought.
How Controversial are Volcanic CFCs?
In his book, a short history of planet earth, Plimer (2001, p. 200) reports that in 1991, Mt Pinatubo released massive quantities of CFCs. Interestingly, nobody disagreed and the book won Plimer the Reed New Holland 2002 Eureka Science Book Prize. However, when Plimer (2009) went on to make a similar statement, this time in Heaven and Earth: Global Warming, the Missing Science, this statement was given quite a different reception.
Plimer (2009, p. 217) underpins his Pinatubo CFC claim with Brasseaur & Granier (1992). As it turns out, Brasseur & Granier (1992) go to some lengths to point out that they are only taking anthropogenic CFCs into account and make neither measurement nor estimate of volcanic CFCs. Although misquotes are quite common in the literature (eg. Whitaker, 2007, p. 137; misattributes the graph by Michael Mann to the "Bureau of Meteorology"), the typical reaction of Plimer's opposition is to revel in Plimer's apparent ignorance of the "fact" that CFCs are strictly anthropogenic. The attitude that only anthropogenic CFCs affect climate is not new. Roscoe (2001) states:
Ozone depletion at mid-latitudes is caused by reactive halogens from man-made halocarbons. The stratospheric sulphate aerosol which follows large volcanic eruptions enhances (multiplies) this ozone depletion (it has no effect on ozone without halocarbons).
This statement assumes that stratospheric sulphate aerosols (produced by volcanic eruption) are not accompanied by volcanic CFCs. However, it is a foregone conclusion that CFCs are not naturally occurring substances, as demonstrated by Flannery (2005, p.31):
The rarest of all the greenhouse gases are members of the HFC & CFC families of chemicals. These children of human ingenuity did not exist before industrial chemists began to manufacture them.
Albuterol MDIs were initially formulated with CFC propellants. CFCs are not naturally occurring compounds.
Colice (2007, p. 15):
CFCs and the Environment
CFCs are not naturally occurring chemicals. Frederic Swarts pioneered fluorocarbon chemistry in the late 1890s. In 1928, two scientists in the Frigidaire Division of General Motors selected CFC-12 as an ideal refrigerant for home refrigerators.
And Hendeles et al. (2007):
[...] with CFC albuterol inhalers. Political and Regulatory Mandates. CFCs are not naturally occurring substances. When developed in the [...]
This idea that CFCs do not occur naturally is further stated by Warrick & Farmer (1990), Grimston (1992), and Mazur & Lee (1993). Thus it comes as no surprise that methodology is influenced by what apears to be a widely acepted idea (Green & Stewart, 2008, p. 18):
The age dating estimates of groundwater samples were achieved using carbon-14 and CFC-11 and CFC-12 dating techniques. These techniques are effective in different age ranges: carbon-14 dating being useful for samples of ages greater than 100-200 years; while CFC dating is effective only for groundwaters that have recharge since 1965. As CFCs are not natural in the environment and did not exist in the atmosphere until approximately 1965, groundwater recharged prior to that year should have CFC concentrations that are zero or below detection levels.
It appears that even accepted methods such as CFC dating are based on the widely accepted idea that CFCs are not natural.
Water Solubility & Weight Precluded Volcanic Emissions
When the patents on conventional refrigerants were due to expire, the thinning of the ozone layer was deftly correlated with CFC usage and the correlation cross-referenced with chemistry indicating the breakdown of ozone in the presence of CFCs. When it was regularly pointed out that volcanoes erupt large quantities of chlorine and fluorine, proponents of the ozone disaster glibly stated that all volcanogenic emissions that could effect the ozone layer were either water soluble or otherwise too heavy to remain in the stratosphere for significant periods of time.
Plume Chemistry that Overcomes Water Solubility & Weight Issues
The focus of the movement to save the ozone layer is CFCs and not halocarbons in general. Interestingly, this fuss over CFCs excludes other, more potent halocarbons such as bromomethane. Although bromine is 40 times as potent as chlorine in the breakdown of the ozone layer it is ignored by in favour of halocarbons in common use, namely CFCs. Those who may be inclined to point out that bromocarbons and bromohalocarbons are heavy and are not carried up into the stratosphere omit the fact that significant quantities of such gases are produced by magmatic (Bureau, 2000) and volcanic processes (Schwandner et al., 2002, 2004). As such, these gases along with significant quantities of far heavier dust, regularly rise on volcanic plumes into the stratosphere. Noteworthy eruptions of this magnitude include Pinatubo (Philippines, 1991), Gunung Agung (Bali, 1963), Katmai (Alaska, 1912), Santa Maria (Guatemala, 1902), Krakatoa (Indonesia, 1883), Tambora (Indonesia, 1815), and Laki (Iceland, 1783-1784). These are all still relatively minor eruptions except for Laki, which released enough sulphur to generate 250 megatons of sulphuric acid aerosol, in addition to 7 megatons of HF (hydrofluoric acid aerosol) and 15 megatons of HCl (hydrochloric acid aerosol).
"CFCs are not Volcanic" - Oh Really?
This statement is one that I keep seeing on websites and blogs, and ties in with the assertions repeated by Warrick & Farmer (1990), Grimston (1992), Hendeles et al. (2007), Colice (2007), Colice (2008), and Green & Stewart (2008, p. 18) to the effect that CFCs are not natural in the environment. If one chooses to measure the gases emerging from volcanic vents instead of taking a politician's word for it, one discovers that volcanoes produce a variety of halocarbons, including CFCs. This fact, along with other natural sources of CFCs including sponges, other marine animals, bacteria (both marine & terrestrial), fungi (both marine & terrestrial), plants (both marine & terrestrial), lichen, insects, is so well documented that it is the subject of ongoing textbook publication (Gribble, 2003; Jordan, 2003). Stoiber et al. (1971) first measured and documented CFCs venting from Santiaguito in Guatamala. Since, there have been many studies corroborating the volcanic emission of CFCs (Isidorov et al, 1990; Isidorov et al., 1993; Jordon et al., 2000; Schwandner et al., 2000; Schwandner et al., 2002; Schwandner et al., 2004; Frische et al., 2006). Although some authors attempt to correlate volcanogenic CFCs to atmospheric variations, the confirmation of soil diffusion decay with distance from the vent (Schwandner et al., 2004) still stands in stark contradiction of Frische's hypothesis.
Omitted Reaction Series
Elements of the typical volcanic plume chemistry such as HCl & HF in the presence of other halocarbons (such as bromomethane) and hydrocarbons, will substitute chlorine and fluorine for bromine, favouring a halocarbon light enough to remain long term in the stratosphere, while the heaviest (eg. bromine) ion returns to earth in water soluble form without the rest of the halocarbon. The hypothesis that volcanic chlorine & fluorine is removed from the atmosphere by precipitation omits the fact that lighter halogens are favoured by halocarbons while heavier halogens are favoured by water soluble acid formation. This ensures that once the bromine has done its damage, lighter halogens are then combined with non-polar chemicals that are too light to settle out, and neither sufficiently water soluble nor hydrophylic to be removed from the stratosphere by precipitation. Furthermore, the surface of the volcanic aerosol not only provides an increased surface area on which ozone can be broken down, but additionally increases the fraction of stratospheric halogen that occurs in ozone destroying forms - as observed in the substantial increase in the ozone destroying forms of chlorine by Wilson et al., (1993).
The Awful Truth about Plimer, Volcanoes, and CFCs
As it turns out, Plimer was dead right about the production of CFCs by volcanic processes. He may have misattributed this to the wrong source, but he was still dead right. What about Mt Pinatubo you may ask? Bureau et al. (2000) determined that the eruption of Mt Pinatubo released between 15 and 25 kilotons of Bromine, which in the form of bromocarbons as observed in other locations (eg. Schwandner et al. 2004), and in the presence of large quantities of HCL and HF, would undergo a substitution reaction to produce sufficient CFCs to have a prolonged effect. The impact of this was observed in the wake of the Pinatubo Eruption with substantial increases in ClO and in particular the substantial increase in the ozone destroying forms of chlorine as a product of Pinatubo's emissions (Wilson et al., 1993). Aiuppa et al. (2005) determined that ongoing passive emissions from Mount Pinatubo alone include 700 tons of bromine and 10 tons of iodine annually. As halocarbons, it is inevitable that these recombine with more reactive halogens found in abundant volcanogenic acids such as HCl and HF to form CFCs, HI, and HBr.
In spite of numerous erroneous academic assertions, CFCs are naturally occurring chemicals and are a significant component of active volcanism. Volcanic CFCs are emitted in the presence of compounds that raise the residence time of volcanic halogens in addition to intensifying their ozone damaging effect. This would suggest that volcanoes have had a significant impact on the ozone layer. Furthermore, when someone like Plimer appears to misquote one source, it is likely that it is the source that is misattributed and that underpinning can be found elsewhere for the assertion. It is just a matter of looking.
Aiuppa, A., Federico, C., Franco, A. Giudice, G., Gurrieri, S., Inguaggiato, S., Liuzzo, M. McGonigle, A. J. S., & Valenza, M., 2005, "Emission of bromine & iodine from Mount Etna volcano", Geochemistry Geophysics Geosystems, Vol. 6, American Geophysical Union, DOI: 10.1029/2005GC000965
Brasseur, G. & Granier, C., 1992, "Mount Pinatubo aerosols, chlorofluorocarbons, and ozone depletion.", Science, Vol. 257, p. 1239-1242
Bureau, H., Keppler, H., & Metrich, N., 2000, "Volcanic degassing of bromine and iodine: experimental fluid/melt partitioning data and applications to stratospheric chemistry", Earth & Planetary Science Letters, Vol. 183, pp. 51-60
Butler, J. H., 2000, "Atmospheric chemistry: Better budgets for methyl halides?", Nature, Vol. 403, p. 260-261
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