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.
Fascinating, Jim!
Persistent Organic Pollutants (POPs) including chlorinated substances have long been measured the Arctic. This research may point to a new, natural mechanism for the formation of chlorinated substances. Of course, the Industrialized West has been blamed for this pollution and its health effects upon indigenous Arctic peoples:
http://www.panap.net/issues/pesticides-health-and-environment/persistent-organic-pollutants-pops-and-indigenous-people-arctic
Folks snickered when Pres. Reagan said that trees caused pollution, but years later, this was also proven. https://earthdata.nasa.gov/featured-stories/featured-research/volatile-trees
Excellent synopsis Ferdinand!
Even with your answer back to Anthony, I agree with Anthony’s request. Only I don’t think you need to file an official rebuttal, just the chemical synopsis and link to the 1998 paper.
Darn good comments Lewis and Steve!
I was chewing over how O₂; (ozone) managed to act like a battery in causing electrolysis of seawater to release free chlorine atoms. Bit Ferdinand’s synopsis is far more likely. Since ozone quickly reacts away, without UV to drive the ozone production the reaction would cease at night, all six months of it.
Electrolysis of sea salt solution disassociates the salt. This is one way to produce sodium hypochlorite (bleach) as an end result (NaCl => Na+ ClO- +H₂O). A process used by backcountry people (hikers, campers, military) to sterilize their drinking water.
I was also curious why the ‘researchers’ ,(cough cough) didn’t look for the normal ‘suspects’ when free chlorine is found, like all of the metals it is so delightfully reactive with; for that matter ozone is also quite happy to react with metals too.
Add to that the idea that the ‘researchers’ also claim hypobromous acid is formed because of free chlorine and O2₂ floating around. Imagine that!
I was under the impression that chlorine was more reactive than bromine and O₂ topped them both. Why blame chlorine?
I also wondered why iodine wasn’t mentioned as it is certainly common in the sea.
As for mercury, as Gail Combs mentioned, mercury and mercury compounds are common in many areas of Earth’s crust. Some areas even have elemental mercury pooling freely until it gets exposed to air. An odd note is that many of the ‘recent’ papers claiming to prove oceanic mercury levels (methylmercury) are human caused, are mostly based on ‘models’… Sound familiar?
Izen is spreading p’izen knowledge huh? Well, weeds and trolls hate to keep their waste of space and filth all to themselves.
Don’t forget that earth’s magnetosphere causes high energy particles to enter at the magnet pole; some of these are seen as the aurora borealis.
I wonder if the chlorine molecules go away in the Arctic spring night (average low in March in barrow -28.4°C) because chlorine is a liquid below -34°C? Did the researchers measure the temperature whilst sampling?
Whilst we’re fretting about mercury in the food chain; spare a thought for those ignorant Californians who are terrified of radiation (from Japan) who are totally unaware of the polonium-210 constantly in the food chain:
http://www.acsa2000.net/HealthAlert/RadioFood.html
Well, with the help of Judith Curry, I received the full article directly from Dr. Huey…
In the article there is not the slightest hint of melting ice or local/global warming in the Arctic. So far for the discrepancy with the press release…
There is more than enough seasalt in the snowpack over the Arctic ocean and land (as measured during the campaign) that may be the source of chlorine detected. The main cause in this case being the oxydation of chloride to chlorine by ozone and light: there is no detectable free chlorine if the ozone concentration is too low and the chlorine levels drop to zero at night. Chlorine levels also drop somewhat around midday, as the more intense sunlight dissociates Cl2 into Cl radicals which are very reactive and react near immediately with organics and other halogen inorganics (bromides, iodides and derivatives). This was measured as an increased level of organic and inorganic peroxy radicals.
Further, the high chlorine levels were detected near ground up to a few meters, which points to a ground source, which may be salt spray on snow or ice, seems like more solid surface chemistry.
Similar releases of bromine and iodine were detected in the past, but this is the first time for chlorine.
Last but not least, the authors warn:
“high levels of Cl2 observed at Barrow do not imply high levels of Cl2 in the entire Arctic.”
My impression is that the research was set up profesionally and well done, but no conclusion can be derived from a single measurement series on a single place over a short period of time…
Anyway the hints on melting ice in the press release and the interview with Dr. Huey have not the slightest base in the research itself, but may have helped its publication… And if the salt spray at the snow/ice surface is the main source, less ice would give less chlorine, not more?
Billy Liar says:
January 15, 2014 at 1:58 pm
I wonder if the chlorine molecules go away in the Arctic spring night (average low in March in barrow -28.4°C) because chlorine is a liquid below -34°C? Did the researchers measure the temperature whilst sampling?
Not a chance: water is a liquid below 100°C, but that doesn’t say that all water drops out of the atmosphere below that temeperature. It is a matter of vapour pressure for water, CO2 and chlorine alike. Because of the very low concentrations no liquid chlorine will form, but around -80°C, some strange chemicals (chlorine nitrate) are formed on the surface of the ice crystals of stratospheric clouds. That reacts with HCl to form chlorine, which reduces ozone in spring…
richardscourtney says: @ur momisugly January 15, 2014 at 8:10 am
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.
>>>>>>>>>
I will second that. Ferdinand’s comment was very well done.
RichardsCourtney … what makes you feel you can verbally abuse people at will on this site? I guess your Christian name was given for good reason!
So there is salt trapped in the ice, and the salt evaporates and dissociates into chlorine, which kills the ozone over the arctic. Izzere an arctic ozone hole ?? I always thought the ice was fresh water. I believe the segregation coefficient says the salt prefers the liquid phase (of water) to the solid phase, so it gets expelled back into the ocean, as the seawater freezes. The CO2 in the arctic ocean also gets expelled from the ice, when the water freezes (same reason), and that results in the ocean water adjacent to the ice being super-saturated with CO2, so the ocean water then expels the excess to the atmosphere; which is why the atmospheric CO2 over the arctic has a p-p cycle of 18-20 ppm over the seasons, compared to 6 ppm at Mauna Loa.
Yeah I know there are brine pockets in the ice; but that has to be peanuts of salt, compared to what is expelled to the water on freezing; and it would be hard to convince me, that on melting of that ice, that brine gets exposed to the atmosphere preferentially, rather than just slipping into the warm ocean that is causing the ice melt anyway.
izen says:
January 15, 2014 at 3:25 am
“Given that at least half of the background mercury levels we measure are human made, that is that anthropogenic sources have doubled the natural background level, {Munthe et al 2001} at least half the mercury measured anywhere must be from human activity releasing it from natural sequestration.”
Yeah, especially these Chinese curly light bulbs for saving the environment. I think we will be seeing a big spike in Hg over the next decade or so.
Re molecular chlorine in the arctic, getting the source of the chlorine wrong, it would be another level of abstraction for these guys to expect the solar wind’s ionized particles that give rise to the aurora as good candidates for splitting off Cl from NaCl which is abundantly in the air or, more likely, Ferdinand’s HCl.
Interestingly, a way to recover spent HCl (conversion to salts) in industrial processes is to react the resulting salts with sulphuric acid:
e.g.
2NaCl + H2SO4 => 2HCl + Na2SO4.
Sulphates are abundant in the atmosphere and the sea, too! Hey, how about protons from the solar wind (which are H^+) + sulphates in the atmosphere from volcanism and blown/evaporated seawater chlorides giving us HCl. The sun may have more than one way to effect climate!
Wherever this chlorine comes from, it’s still a WW1 poison gas.
So I’m pleased to be able to say we’re still doomed.
This recently published article may be relevant:
Production of gas phase NO2 and halogens from the photolysis of thin water films containing nitrate, chloride and bromide ions at room temperature
Nicole K. Richards-Henderson,a Karen M. Callahan,a Paul Nissenson,b Noriko Nishino,a Douglas J. Tobias*a and Barbara J. Finlayson-Pitts*a
Phys. Chem. Chem. Phys., 2013,15, 17636-17646
UV light generating molecular chlorine and NO2. Pay-walled, so I can’t read the details; I don’t know for sure if the reaction was done in the presence of air or not… but I assume it was..
This Russian group shows that the reaction is ozone with sodium chloride to form hypochlorite ion:
Kinetics and Catalysis
August 2010, Volume 51, Issue 4, pp 492-496
Mechanism and kinetics of the reaction of ozone with sodium chloride in aqueous solutions
S. D. Razumovskii, M. L. Konstantinova, T. V. Grinevich, G. V. Korovina, V. Ya. Zaitsev
Sodium hypochlorite could react with H+ (probably from CO2 + H2O –> H+ + HCO3- ) to form Cl2 plus sodium bicarbonate. So the reaction may take place in the relatively concentrated saline solution that forms when sea ice forms, and the initial product is hypochlorite from ozone reacting with HCl. Makes sense: only during daytime (ozone), only near the surface, and only where ice forms from seawater, generating a residual salt solution of relatively high concentration on the ice surface.
All those studies over the last couple decades on fluorine from Freon, and they never once checked for chlorine?
We have a pretty obvious problem with our research data gathering agenda.
“On Lonely Mission, Robot Starts Descent Into Volcano”. This article appeared in the NYT on 16th Jan 1993 and referred to NASA’s Dante robot mission into Mount Erebus in the Antarctic. The purpose was to examine gaseous emissions from the volcano, expected to contain significant volumes of Chlorine. The robot failed after a short run due to a break in the optical fibre link. It was withdrawn and never heard from again?
There was some UK TV programme based on this Expedition, but I am unable to locate it so far.
How about volcanic emissions as the source of whatever form of Chlorine has been detected?
Caleb says:
January 15, 2014 at 3:05 am
Can chlorine oxidize? Or does oxidization have to involve oxygen?
Yes, chlorine is an oxidising agent, where oxidation is defined in terms of gaining or losing electrons. Here, the reactant which gains electrons is the oxidizing agent, while the reactant which has lost electrons has been oxidized. Molecular chlorine gains two electrons to end up as two chloride ions.
stevefitzpatrick says:
January 15, 2014 at 6:06 pm
This Russian group shows that the reaction is ozone with sodium chloride to form hypochlorite ion:
That may nail it down: it may be a reaction of ozone with salt spray on ice and snow (thin film reaction) and/or at the surface of brine ponds leftover from the freezing ice.
But it doesn’t explain that the chlorine levels are independent of wind direction: Salt spray is limited in level and extent farther away from the oceans, although most of the chlorine seems to be formed in the direct neighbourhood.
At the other side, methyl chloride (chloromethane) is relative abundant in the lower troposphere, and especially over the oceans, where a lot is formed by algue:
http://www.inchem.org/documents/cicads/cicads/cicad28.htm#_28ci4000
The concentration reaches 1.2 µg/m3 (0.6 ppb) in ambient air, compared to an average surface snow chloride of 6.6 ppmv, but methyl chloride is continuously replenished from the oceans (and land sources), locally or from other places on earth.
From the above reference:
The tropospheric reactive chlorine burden of approximately 8.3 × 106 tonnes chlorine is dominated by methyl chloride (~45%) and trichloroethane (~25%).
The reaction mechanism is not given, but probably also by ozone/high energy light. The original referenced abstract is here:
http://onlinelibrary.wiley.com/doi/10.1029/94GB03103/abstract
According to the research at Barrow, there is no correlation with (salt) aerosols, which can be a fast source. Thus the real origin of the local high chlorine levels still is unknown. It is a pity that the researchers didn’t measure local methyl chloride levels…
I’m pressed for time, and could only scan about 50% of the discussion thread to this point, but it seems there is no WUWT consensus on the source of the chlorine (jape intended).
I propose the following:
Seawater gets carried up into the atmosphere as liquid aerosols, and the water evaporates into vapor, leaving microscopic crystals of NaCl as a solid aerosol, which can migrate into the upper levels of the atmosphere. There, full strength UV will split atomic chlorine from the sodium. The chlorine will then recombine into molecular chlorine and, upon further interaction with UV, split again, recombine again, etc.
Nice hypothesis. Any reason to believe it? There is an atmospheric layer of ionized sodium at high altitude. This is used for “guidestar” laser probes, which sample the optical properties of the atmosphere in order to adjust modern telescopes equipped with adaptive optics. They project a laser beam on a line parallel to the optical axis of the telescope and measure the optical distortion of the light scattered or re-radiated by the sodium layer.
I simply ask: Whence came the sodium layer?
It makes the perfect counterpart to: Whence came the chlorine?
izen says:
January 15, 2014 at 7:59 am
No, historical data on mercury levels preserved in human and animal hard tissues shows clearly that the natural background level was far below present levels until around the 1850s. Then industrial extraction massively increased the environmental levels with the elemental mercury we emit spreading worldwide, its conversion to soluble divalent mercury causes it to end up in the oceans where it is concentrated into the food chain. Pre-industrial samples do not show anything like the present day levels of mercury contaminattion of the seas or the food chain.
—————–
I’d like to see a citation on this claim. Here’s one citation that gives a counter argument:
http://www.ncbi.nlm.nih.gov/pubmed/5060046
Science. 1972 Mar 10;175(4026):1121-2.
Mercury concentrations in museum specimens of tuna and swordfish.
Miller GE, Grant PM, Kishore R, Steinkruger FJ, Rowland FS, Guinn VP.
Abstract
The mercury levels of museum specimens of seven tuna caught 62 to 93 years ago and a swordfish caught 25 years ago have been determined by instrumental neutron activation analysis. These levels are in the same range as those found in specimens caught recently.
————
The mercury in tuna scare began in the late 1960s due to Japanese industrial pollutants in tuna and other locally caught fish causing massive health problems in some Japanese locations. This study (of which one author was Frank Rowland, of Rowland and Molina fame – i.e. the guys who linked ozone depletion with Freon) found no difference in mercury levels between recently caught fish and museum samples dating back to a century earlier. The samples were all from the high seas. Obviously, mercury concentrations in farmed fish in Japanese inshore waters would be much higher. Japan has an intensive fish farming culture that dates back to the 1930s, by the way.
In my time of military duty in the 70’s and 80’s we learned that to survive in the arctic you should look for old sea ice because it would have less salt in it and i am not a chemist but that tells me that salt can be coming out of the ice by other means.