From the Georgia Institute of Technology
Scientists studying the atmosphere above Barrow, Alaska, have discovered unprecedented levels of molecular chlorine in the air, a new study reports.
Molecular chlorine, from sea salt released by melting sea ice, reacts with sunlight to produce chlorine atoms. These chlorine atoms are highly reactive and can oxidize many constituents of the atmosphere including methane and elemental mercury, as well activate bromine chemistry, which is an even stronger oxidant of elemental mercury. Oxidized mercury is more reactive and can be deposited to the Arctic ecosystem.
The study is the first time that molecular chlorine has been measured in the Arctic, and the first time that scientists have documented such high levels of molecular chlorine in the atmosphere.
“No one expected there to be this level of chlorine in Barrow or in polar regions,” said Greg Huey, a professor in the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology in Atlanta.
The study was published January 12 in the journal Nature Geoscience and was supported by the National Science Foundation (NSF), part of the international multidisciplinary OASIS program.
The researchers directly measured molecular chlorine levels in the Arctic in the spring of 2009 over a six-week period using chemical ionization mass spectrometry. At first the scientists were skeptical of their data, so they spent several years running other experiments to ensure their findings were accurate.
The level of molecular chlorine above Barrow was measured as high as 400 parts per trillion, which is a high concentration considering that chlorine atoms are short –lived in the atmosphere because they are strong oxidants and are highly reactive with other atmospheric chemicals.
Molecular chlorine concentrations peaked in the early morning and late afternoon, and fell to near-zero levels at night. Average daytime molecular chlorine levels were correlated with ozone concentrations, suggesting that sunlight and ozone may be required for molecular chlorine formation.
Previous Arctic studies have documented high levels of oxidized mercury in Barrow and other polar regions. The major source of elemental mercury in the Arctic regions is coal-burning plants around the world. In the spring in Barrow, ozone and elemental mercury are often depleted from the atmosphere when halogens — chlorine and bromine — are released into the air from melting sea ice.
“Molecular chlorine is so reactive that it’s going to have a very strong influence on atmospheric chemistry,” Huey said.
Chlorine atoms are the dominant oxidant in Barrow, the study found. The area is part of a region with otherwise low levels of oxidants in the atmosphere, due to the lack of water vapor and ozone, which are the major precursors to making oxidants in many urban areas.
In Barrow, snow-covered ice pack extends in every directly except inland. The ultimate source of the molecular chlorine is the sodium chloride in sea salt, Huey said, most likely from the snow-covered ice pack. How the sea salt is transformed into molecular chlorine is unknown.
“We don’t really know the mechanism. It’s a mystery to us right now,” Huey said. “But the sea ice is changing dramatically, so we’re in a time where we have absolutely no predictive power over what’s going to happen to this chemistry. We’re really in the dark about the chlorine.”
Scientists do know that sea ice is rapidly changing, Huey said. The sea ice that lasts from one winter to the next winter is decreasing. This has created a larger area of melted ice, and more ice that comes and goes with the seasons. This seasonal variation in ice could release more molecular chlorine into the atmosphere.
“There is definite climate change happening in the Arctic,” Huey said. “That’s changing the nature of the ice, changing the volume of the ice, changing the surface
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High levels of molecular chlorine in the Arctic atmosphere
Liao et al, Nature Geoscience (2014) doi:10.1038/ngeo2046
Abstract
Chlorine radicals can function as a strong atmospheric oxidant1, 2, 3, particularly in polar regions, where levels of hydroxyl radicals are low. In the atmosphere, chlorine radicals expedite the degradation of methane4, 5, 6 and tropospheric ozone4, 7, and the oxidation of mercury to more toxic forms3. Here we present direct measurements of molecular chlorine levels in the Arctic marine boundary layer in Barrow, Alaska, collected in the spring of 2009 over a six-week period using chemical ionization mass spectrometry. We report high levels of molecular chlorine, of up to 400 pptv. Concentrations peaked in the early morning and late afternoon, and fell to near-zero levels at night. Average daytime molecular chlorine levels were correlated with ozone concentrations, suggesting that sunlight and ozone are required for molecular chlorine formation. Using a time-dependent box model, we estimate that the chlorine radicals produced from the photolysis of molecular chlorine oxidized more methane than hydroxyl radicals, on average, and enhanced the abundance of short-lived peroxy radicals. Elevated hydroperoxyl radical levels, in turn, promoted the formation of hypobromous acid, which catalyses mercury oxidation and the breakdown of tropospheric ozone. We therefore suggest that molecular chlorine exerts a significant effect on the atmospheric chemistry of the Arctic.
Kent Jeffreys says:
January 15, 2014 at 7:19 am
I see from the photo at the press release that at least one of the instruments used by these researchers was attached directly to plywood. Any chance that part of their chlorine measurement resulted from emissions from the plywood?
>>>>>>>>>>>>>
Possibly. Polychlorinated dibenzo-p-dioxins and dibenzofurans in plywood combustion gas
When you are talking a half part per million it does not take much to get contamination.
Chlorine in breath condensate–a measure of airway affection in pollinosis?
I wonder if anyone handling the equipment had asthma or allergies….
Mike Ozanne:
At January 15, 2014 at 7:39 am you ask
The answer to your first question is, probably.
Ferdinand Engelbeen gave an excellent answer to your second question(s) in his first post so I again link to it to save you needing to find it.
http://wattsupwiththat.com/2014/01/15/high-levels-of-molecular-chlorine-found-in-arctic-atmosphere/#comment-1536483
Richard
PS You may not know that Ferdinand and I have been strong protagonists for many years so my evaluation of the high quality of his post is not biased.
Ferdinand Engelbeen says:
January 15, 2014 at 2:10 am
==
Thank you sir.
Back in the early days of handwringing about the ozone hole, there was an article in Science News about meythl chloride release from sea water as a potential source of stratosperic chlorine. I can’t find the article, but here are a few more complete references.
http://www.inchem.org/documents/cicads/cicads/cicad28.htm#_28ci4000
Natural sources of methyl chloride dominate over anthropogenic sources…
Over the Pacific Ocean, the concentration of methyl chloride is higher in the lower troposphere than in the higher layers. However, over the continents, the concentration is independent of the altitude. Thus, the ocean seems to be a source of methyl chloride (Geckeler & Eberhardt, 1995). In the oceans, algae, especially planktonic algae, are considered to be responsible for most of the methyl chloride production. However, this has not been fully proven.
http://www.ccpo.odu.edu/~lizsmith/SEES/ozone/class/Chap_10/10_4.htm
4.2 Ocean Production of Methyl Chloride and Methyl Bromide
Biological activity in the ocean processes some of the dissolved chlorine, bromine, and iodine salts. Seaweed produces methyl iodide (CH3I). Reactions in seawater replace the iodine with bromine to produce methyl bromide (CH3Br). Further reactions replace bromine with chlorine to produce methyl chloride (CH3Cl). A portion of each of these substances escapes to the atmosphere. CH3Br from the atmosphere may also dissolve in the ocean and be converted to CH3Cl. Methyl chloride has an atmospheric residence time of 1.5 years and is the most important natural source of chlorine for the stratosphere.
http://www.ess.uci.edu/pub/714
Title: Methyl chloride in a deep ice core from Siple Dome, Antarctica
Abstract: Methyl chloride (CH3Cl) is a naturally occurring ozone-depleting substance and a significant component of the atmospheric chlorine burden. In this study CH3Cl was analyzed in air bubbles from the West Antarctic Siple Dome deep ice core with gas ages ranging from about 65 kyr BP to the Late Holocene. CH3Cl levels were below the modern Antarctic atmospheric level of 530 ppt in glacial ice ( 456 +/- 46 ppt, 33-65 kyr BP) and above it during the early Holocene (650-700 ppt, 10-11 kyr BP). For most of the Holocene, CH3Cl levels were 500-550 ppt, with good agreement between CH3Cl levels in this core and in the Dome Fuji ice core (Saito et al., 2007). Several late Holocene ice core samples (< 2 kyr BP), show evidence of enrichment in CH3Cl relative to South Pole ice core samples of overlapping gas age. The Siple Dome record suggests that CH3Cl levels in the glacial Southern Hemisphere atmosphere were about 16% lower than those during the mid-late Holocene. Citation: Saltzman, E. S., M. Aydin, M. B. Williams, K. R. Verhulst, and B. Gun ( 2009), Methyl chloride in a deep ice core from Siple Dome, Antarctica, Geophys. Res. Lett., 36, L03822, doi: 10.1029/2008GL036266.
So, don't blame me for the chlorine in the atmosphere!
Ferdinand Engelbeen says:
January 15, 2014 at 2:10 am
Also, from one of my refs in the post I just made (three URLs an into the moderation queue) is this confirmation:
http://www.ccpo.odu.edu/~lizsmith/SEES/ozone/class/Chap_10/10_4.htm
4.1 Sea Salt Production of Sodium Chloride (NaCl) and Hydrochoric Acid (HCl)
The most common source of chlorine to the atmosphere is sea salt spray. Breaking waves and wind-blown foam spray millions of tiny particles and gases into the atmosphere. The tiny particles contain dissolved sodium chloride (NaCl or ordinary table salt). As the particles evaporate, both NaCl and hydrogen chloride (HCl) are released as a gas. Both of these molecules are highly soluble, and are removed by redissolving in the ocean or by dissolving in rainwater and being redeposited in the ocean or on land. Their atmospheric residence time is of the order of one week and they contribute negligible amounts of chlorine to the stratosphere.
4.2 Ocean Production of Methyl Chloride and Methyl Bromide [I quoted this before]
Biological activity in the ocean processes some of the dissolved chlorine, bromine, and iodine salts. Seaweed produces methyl iodide (CH3I). Reactions in seawater replace the iodine with bromine to produce methyl bromide (CH3Br). Further reactions replace bromine with chlorine to produce methyl chloride (CH3Cl). A portion of each of these substances escapes to the atmosphere. CH3Br from the atmosphere may also dissolve in the ocean and be converted to CH3Cl. Methyl chloride has an atmospheric residence time of 1.5 years and is the most important natural source of chlorine for the stratosphere.
Izen,
Since many readers here are unwilling to pay 35.95 to read Munthie et al, perhaps you can explain their basis for knowing the percentage of human contribution?
Ferdinand Engelbeen,
My guess is that the molecular chlorine comes from oxidation of NaCl to sodium peroxide plus molecular chlorine. This is energetically favorable because ozone is a much stronger oxidizing agent than is chlorine. Sodium peroxide formed this way would be expected to react quickly with water vapor in the air to yield NaOH. NaOH reacts quickly with CO2 to yield sodium carbonate, and then further with water and more CO2 to yield sodium bicarbonate. Of course, the detailed mechanism of the formation of chlorine might involve catalysis with some other species.
The relative oxidation potentials are shown here http://www.ozoneapplications.com/info/oxidizing_potential_of_ozone.htm
An old preparation method for sodium peroxide was reaction of solid sodium iodide with ozone, yielding molecular iodine (a palladium tube was used to speed the reaction via catalysis, mechanism unknown). Iodine is easier to reduce than chlorine, of course, but ozone is still a much stronger oxidizing agent than chlorine.
The observation that the chlorine level correlates strongly with ozone and drops to near zero at night, combined with the requirement of a very strong oxidizing agent (sufficient to reduce Cl ion to Cl2) indicate a direct reaction of ozone with NaCl as most likely.
Ferdinand Engelbeen: UV is not the only “light” that will disassociate NaCl in solution. Gamma and Xray also – All are omnipresent to a degree. GK
Interesting that there is a diurnal cycle from 0-400 ppt. Does this not imply that Cl- ions can be released into the atmosphere from salt spray (from melting sea ice, wtf?) in sufficient quantities each day to reach the stratosphere in our polar deserts where there isn’t enough precipitation to wash it out of the air?
Anthony Watts says:
January 15, 2014 at 5:20 am
Ferdinand, an excellent synopsis. May I suggest that you write a letter of rebuttal to Nature Geoscience on this? See: http://www.nature.com/ngeo/authors/index.html
Thanks Anthony and others. I think we were -again- put on the wrong leg by some PR guy who wrote the press release. I haven’t baught the article (did give up that as what they ask for money is a shame, especially if one want to read a lot of related articles at once), and have no time to go to the university’s library in the next 1.5 week (visit to Valencia, Spain), But I may ask it Judith Curry, working in the same institute… Or if someone has access to Nature Geosciences articles…
On the other hand, their supplementary information is free and excellent:
http://www.nature.com/ngeo/journal/vaop/ncurrent/extref/ngeo2046-s1.pdf
From chapter 4 in the SI:
In summary, we found no clear relation between the age of the sea ice and chlorine levels. We also found no clear directional preference. High chlorine levels were found to correspond to long residence times in the boundary layer within 500 km of Barrow independent of wind direction.
Thus independent of the origin of the air coming in over ice/open ocean/land (snow/vegetation)? There is no direct link I see with ice/snow melting and/or a larger open sea surface…
Both HCl and Cl2 have short life times in the atmosphere (4 hours and 10 minutes resp.), thus are produced in situ from a precursor (which thus isn’t HCl itself), absorb on the snow surface and/or react with other species (organics, O3,…) in the atmosphere, aerosols and on the snow surface. The latter, solid surface reactions, are very complicated and hardly known in detail…
They measured a lot of species, but I haven’t seen a direct link to CH3Cl (methylchloride) which can be the source of the continuous supply of chlorine/HCl precursors in the Arctic…
citizenkla says:
January 15, 2014 at 7:04 am
Did you mean Chlorine – VCM – PVC? with a butadiene inhibitor for bulk shipment of the VCM?
Indeed: at that time 325,000 tonnes per annum chlorine and 500,000 tonnes VCM, mostly used locally to produce PVC. Since my retirement they expanded the (membrane) chlorine factory to 500,000 tpa feeding a lot of other production units in the neighbourhood: MDI (for polyurethane), epoxy resin precursors, titanium dioxide (white dye for paints, inks,…)…
MDI manufacturing sends HCl back that then is used again in the VCM oxychlorination process…
Gail Combs says:
January 15, 2014 at 8:05 am
When you are talking a half part per million it does not take much to get contamination.
Chlorine in breath condensate–a measure of airway affection in pollinosis?
I was aware that the white blood cells attack invaders by surrounding them with NaOCl (bleach) and NOx, but I wasn’t aware that the sensitivity of the measurements was already so good that they could measure the increase of chlorine in the exhaled air… Very interesting information!
But I suppose that the researchers were aware of that and stayed away from the direct intake…
Steve Fitzpatrick says:
January 15, 2014 at 8:28 am
My guess is that the molecular chlorine comes from oxidation of NaCl to sodium peroxide plus molecular chlorine.
It is one of the probable mechanisms (I suppose that you mean by O3 for the last part), but as the chlorine levels seems independent of the wind direction and the catch area is about 500 km according to their SI, there should be a drop if the wind direction is from the land side.
Looks more like a continuous supply from another precursor…
Izen says:
“Pre-industrial samples do not show anything like the present day levels of mercury contaminattion of the seas or the food chain.”
Mercury is being dumped in the oceans from leakge by the millions upon millions of consumer flourescent lights that were pushed by your enviro-cronies, Izen. Have you demanded that they must immediately stop producing those curly bulbs?
Or, is it only bad when you can blame it on industry — the same industry that makes your life so much longer, healthier, and more wonderful than it would be without industry?
…Huey said… The sea ice that lasts from one winter to the next winter is decreasing.
Sea ice is decreasing? That’s news to me, and to a lot of readers here.
‘The level of molecular chlorine above Barrow was measured as high as 400 parts per trillion, which is a high concentration considering…’
I now know the way to deal with the U.S. deficit. In April I will make a voluntary contribution; not of four hundred billion dollars, nor of a measly four hundred million, nor even four hundred thousand dollars; no; I will graciously give up a whole two months worth of breakfasts at McDonald’s and contribute a grand total of four hundred dollars – yep, four hundred dollars – for a massive pay down of one trillion dollars of the deficit. And, if just a handful of additional benefactors, each contribute $400.00, the U.S. deficit problem will be solved. And, if that $400.00 cuts into any of their car payments, heck, just give the bank 4 cents that month: they’ll be happy with it.
Trygve Eklund says:
January 15, 2014 at 1:48 am
At that time, we were taught that free chlorine was generated by the action of UV light on sea water.
As we know, sea water has a lot of NaCl in it. And due to the different attractions of Na and Cl for electrons, we have Na+ and Cl-. And it is certainly possible for UV light to knock the extra electron loose from Cl- to form a neutral Cl atom. Then two Cl atoms would combine to form a diatomic Cl2 molecule.
The more sea water that is exposed to sunlight, the more Cl atoms could form. So in this way, if more polar ice melts, more sea water is exposed to the sun and more Cl2 could form. But this is an extremely convoluted way to combine melting polar sea ice with extra Cl2. It makes as much sense as trying to find the weight of a captain by weighing the ship with the captain on it and then weighing it again with the captain off it. The extra area of total ocean water exposed to UV light is an extremely small fraction.
G. Karst says:
January 15, 2014 at 8:30 am
Ferdinand Engelbeen: UV is not the only “light” that will disassociate NaCl in solution. Gamma and Xray also – All are omnipresent to a degree. GK
Agreed, but I suppose that most of the energy reaching the surface in the high energy band is UV…
So chlorine radicals in the polar regions with unknown consequences again. Perhaps this old news is not as dead as we thought as it relates to the ozone hole theory eh?
http://www.nature.com/news/2007/070924/full/449382a.html
“unprecedented”…”The study is the first time that molecular chlorine has been measured in the Arctic”
Funny stuff. “It’s worse than we thought”!
This was measured in 2009, sea ice was lower, including multi year ice.
This is now 2014, sea ice is greater, especially including multi year ice.
They are acting as if the sea ice was still diminishing, as before, when it is actually increasing/back to normal.
They are essentially saying 2009 measurements are 2014 measurements and should be treated as such.
They seem to not know or care what sea ice has been doing lately.
They may not know because they know nothing outside their specialty, and/or they may not care because supporting “the cause” makes them feel good, not supporting it will get them fired, and supporting it supports the governments drive for total control and thus gets them grant money.
Until I see present day measurements, this study is irrelevant.
@Katherine
Well said Katerine. At least you are thinking.
>>The major source of elemental mercury in the Arctic regions is coal-burning plants around the world.
>Yeah? How can they be so sure of that? What’s their basis for this claim? How about all the naturally burning coal seams?
izen and his ilk are really wrong on this one. OMG this has to be repeated so many times….
The main source of mercury in the atmosphere is the OCEANS because it is there where the stuff is available in huge quantities that utterly dwarf AG emissions. Upwelling waters bring masses of it and it emerges from the ocean and can be measured in the air just like anything else.
There is an atmospheric monitoring station at Cape Point (y’all know where that is?) in South Africa which monitors the wind blowing from Antarctica. It has lots of mercury in it because the oceans between RSA and Antarctica pump it out just like everywhere else. If it was ‘down there’ in the deeps for 1500 years it may have an isotope different from some other, but I seriously doubt the claim that the isotope ratio has anything to do with coal burning. There is simply no easy way to nail that down. The whole environment has mercury in it and it forms part of the soil everywhere.
What was VERY interesting about my visit to the Cape Point station is that is that the scientists there found, when they switched from daily to hourly measurements, that the mercury level in the atmosphere occasionally dropped to ZERO for several hours at a time. There has been no explanation of this phenomenon that contradicts all atmospheric circulation models that say mercury is well mixed and constant all over. But it clearly is not.
The emergence of Cl from the ocean can easily explain this vanishing act and it is worth investigating it further.
If there is an air monitoring station at Point Barrow, it should also be measuring airborne mercury and it should show, on an hourly basis, significant changes, maybe dropping if Cl goes up. It may be that the detection method does not differentiate between an Hg+Cl molecule of some sort and gaseous Hg on its own. Or maybe it does. Whatever the case, this is the first solid idea that I have seen since my visit that points in the general direction of a viable answer to the question, “What natural process is capable of stripping all the mercury out of the atmosphere as it passes over the ocean?” We know the process is natural because there is no ‘unnatural’ process going on between Cape Point and Antarctica, so the head honcho said. The monitoring station is a fine piece of work manned by volunteers from around the world.
“How the sea salt is transformed into molecular chlorine is unknown.”
S’obvious, innit. Global warming, any fool can see that.
Nothing an extra few million dollars’ worth of research won’t get to the bottom of.
Twenty four authors. Science by committee?
Excellent review, Ferdinand Englebeen.
I was surprised by the conclusion that molecular chlorine could be produced from brine (sea water) or sodium chloride (sea salt, anhydrous) and UV light. If so, someone would have long ago developed a solar chlor-alkalai process that is much more energy efficient than using electricity and probably much more profitable than simply evaporating sea water for sea salt. Also, having spent a couple decades in the frozen north and having used NaCl as an ice melter, I never noticed chlorine above the sidewalk and drive. Perhaps if these researchers had lived somewhere other than Atlanta, they wouldn’t have suggested this improbable mechanism for chlorine.
And, if it is truly the first Arctic measurement of atmospheric molecular chlorine, I suppose it qualifies as “unprecedented.”