#236      21 min 27 sec
Mercury rising: The impact of distant human activity on Antarctica

Atmospheric chemist Dr Robyn Schofield discusses how industrial pollution makes its way to the pristine Antarctic continent, and explains the chemistry behind the resulting annual mercury deposition events. Presented by Dr Shane Huntington.

"We have doubled the amount of mercury in the atmosphere and so that's significant and we've taken it out of deep deposits and put it into the atmosphere and it stays there - well, it cycles through the biosphere system and we've increased that cycling five times, through doubling it in the atmosphere." -- Dr Robyn Schofield




Dr Robyn Schofield
Dr Robyn Schofield

Dr Robyn Schofield is an atmospheric chemist in the Atmospheric and Oceanic Sciences Group at the University of Melbourne’s School of Earth Sciences. She completed her PhD  jointly at the School of Environmental Sciences at Auckland University and the National Institute of Water and Atmospheric Research at Lauder, Central Otago, New Zealand. Her project on the vertical distribution of Bromine monoxide (BrO) involved conducting and inverting spectroscopic measurements made at both Lauder and Arrival Heights, Antarctica. Robyn spent two years in Boulder, Colorado as a CIRES visiting fellow working at the NOAA Chemical Sciences Division looking at spectroscopy of clouds, aerosols, sulfur, nitrogen and ozone trends, followed by five years at the Alfred Wegener Institute in Potsdam, Germany, as a Humboldt visiting fellow looking at Polar ozone loss kinetics and then a Marie Curie International Incoming Fellow looking at tropical tropopause layer transport of chemical species to the stratosphere. Her current research interests include inverting spectroscopic observations of photochemically changing species; radiative transfer modelling; stratospheric ozone loss kinetics; tropical tropopause layer processes driving stratospheric composition; and microphysical modelling.

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Host: Dr Shane Huntington
Producers: Eric van Bemmel, Kelvin Param
Associate Producer: Dr Dyani Lewis
Audio Engineer: Gavin Nebauer
Voiceover: Nerissa Hannink
Series Creators: Kelvin Param & Eric van Bemmel

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VOICEOVER 
Welcome to Up Close, the research talkshow from the University of Melbourne, Australia. 

SHANE HUNTINGTON
I'm Shane Huntington.  Thanks for joining us.  We often think of Antarctica as a pristine environment that is unaffected by human activity.  However, research has shown us that this is far from true.  Although geographically isolated from our major cities and populations, the interconnected nature of the planet's weather systems links us to Antarctica in complex ways.  Of particular interest and alarm are the affects of human created pollution on this distant polar landscape.In this episode of Up Close we speak to an atmospheric chemist about how our activities closer to home have substantial impact on the Antarctic region.  Dr Robyn Schofield is a research fellow in the Atmospheric and Oceanic Sciences Group at the University of Melbourne's School of Earth Sciences.Welcome to Up Close Robyn.

ROBYN SCHOFIELD
Thank you.

SHANE HUNTINGTON
Robyn, you're an atmospheric chemist and you're looking at the atmosphere in Antarctica in particular.  What's unique about the atmosphere in that part of the world?

ROBYN SCHOFIELD
Well, in Antarctica you've got a much colder atmosphere on the whole.  But you've got all these other factors that come in.  You've got a polar winter and then a polar summer.  So you've got complete darkness.  For example, when I was down in Antarctica I flew in in the middle of August and there was one hour of sunlight and when I flew out at the end of October it was complete sunlight.  So that's pretty strange for all the chemistry.  You go from a regime where you've got no photochemistry going on and then complete photochemistry.  It's completely saturated.

SHANE HUNTINGTON
The biosphere down there must be set on those timeframes.  Is that right?

ROBYN SCHOFIELD
Yeah.  Well, there is not a lot of biology.  Whatever biology there is, is pretty interesting.

SHANE HUNTINGTON
Now, let's talk a bit about the atmosphere, because I guess most people have this image of it just being a whole lot of gases that are all mixed up.

ROBYN SCHOFIELD
Yeah.

SHANE HUNTINGTON
But these gases are in very specific layers.  Can you talk us through what those layers are and, I guess, what keeps them separated?

ROBYN SCHOFIELD
Right.  So we've got the troposphere.  So that's from the ground up to 10 kilometres and then above that we've got the stratosphere and that's 10 to 50 kilometres.  Within that troposphere we've got a boundary layer and that's from the ground up until about two kilometres.The troposphere we have the temperature decreasing, as you increase in altitude and that means that hot air at the surface will rise.  We get convection happening.  We get winds.  On shore breeze is a good example of how those convections can set up during the day, weeks.  So we get all our weather happening.  It's very wet there.  We get all of the plant chemistry happening, interaction with the biosphere.  That's all in the troposphere.  That's what's happening.When we get above that to the stratosphere, we've got the layered, strata and that's where stratosphere comes from and we've got the temperature increasing through that layer and that's happening because we've got ozone there.  We've got a thin layer of ozone.  If we brought that ozone down to the surface it would only be three millimetres thick.  But that protects us from those high UV levels.  That's why we need to protect the ozone layer.So the stratosphere is a stratified layer of very stable air enters there in the topics and descends at the poles.  That process takes six years and the chemistry there is much more settled and you can think of that as where the atmosphere is sort of sleeping and the troposphere has got 85 per cent of the mass of the atmosphere.  The stratosphere really doesn't have a lot of that mass, but extremely important and it's a boundary.  That's what keeps everything in.  It stops mixing.  You don't have the mixing across that layer because of the heating through that layer.  You don't get vertical transport.

SHANE HUNTINGTON
These two sections, so you are saying they sort of cohabitate throughout the entire globe.  But they are only connected at the poles and the equator.  Is that right?

ROBYN SCHOFIELD
Well, that's where the most amount of transport or flux occurs.  But if you've got a big storm, that will punch through into the stratosphere.

SHANE HUNTINGTON
How does the chemistry between these different regions of the atmosphere differ?  You mentioned, of course, that at the lower levels we have all the biosphere interacting.  But what else is going on there in terms of the chemistry?

ROBYN SCHOFIELD
Okay.  So we've got a lot more water in the troposphere.  We've got all the organics in the troposphere and that really - those are complicated systems.  The water will change things that causes deposition.  You've got aerosols, clouds.  You've got surfaces.  Things happen and you have some surfaces in the stratosphere.  I'll come to them in a minute.  But the troposphere is complicated and the chemistry, it can be quite complex.And in the stratosphere, what survives to make it into the stratosphere is generally something that's fairly long lived.  You've got, so methane will make it there, nitrogen dioxide, carbon dioxide.  Oxygen and nitrogen, of course are the biggest constituents within our atmosphere. They're all up there and then you get long lived gases like your chlorofluorocarbons and the halons, these things.  They all make it up into the stratosphere and sulphur, which will form an aerosol layer up there as well.So when we have a massive volcanic eruption, you can get sulphur directly injected into the stratosphere, beautiful sunsets because you've got light coming in and hitting this aerosol and making everything beautiful.  The chemistry up in the stratosphere is generally driven by these chemical families and so we've got the HOx, the NOx, the ClOx and the BrOx.  So these are the bromine chlorine hydrogen and oxygen and nitrogen driven chemical families.In the troposphere you have that as well and then you have a wealth of other chemicals going on, all of the nasties as well.

SHANE HUNTINGTON
I'm Shane Huntington and you're listening to Up Close.  In this episode we're talking about how Antarctica is held hostage to distant human activities, with atmospheric chemist Robyn Schofield.Now, you studied some very specific atmospheric processes.  What part of the atmosphere are you interested in with your work?

ROBYN SCHOFIELD
Well, I am really interested in all of these halogen driven chemical cycles and they occur in the stratosphere.  My background is in stratospheric chemistry.  But, as I said, these processes also happen in the troposphere and these are really reactive species.  Halogen means a salt maker and so they come from sea salt, brine and so they have oceanic sources.  They have volcanic sources and so I'm really interested in these chemicals, because they are really extremely reactive.They form the ozone hole, which is where my initial interest was and they do all sorts of interesting things wherever they are and they row over the sea-ice and that's where they were a real problem.

SHANE HUNTINGTON
So Robyn, amongst all these chemicals that you find in the atmosphere, which ones in particular are you focussing on?

ROBYN SCHOFIELD
So within all these chemical families, what I'm interested in is bromine and how it interacts with the biogeochemical cycle of mercury and where it does this is in the boundary layer, so that lower most part of the atmosphere.  And mercury enters into our atmosphere from fossil fuel burning from volcanoes and so understanding how this bromine cycle is influencing, controlling and deposition events of mercury, is where my interest lies.  Because it's really important to understand the implications of what this means for our food chain, for higher forms of life, the oceans.

SHANE HUNTINGTON
Most of our listeners would be aware of - they've seen mercury, whether it's in a thermometer or other sort of household objects and so forth and they've interacted with that and know it's a liquid.  But…

ROBYN SCHOFIELD
But they shouldn't have…

SHANE HUNTINGTON
Yeah, they hopefully didn't touch it.  But bromine, do we see that in our normal casual lifestyles, or is that something that is one of those periodic elements that we just don't encounter?

ROBYN SCHOFIELD
It is in all sea salt. So there is trace amounts.  Generally, this table salt that you get on the table is sodium chloride.  But you've got traces of bromine, traces of iodine and so these are all of those salt makers.

SHANE HUNTINGTON
So, you have bromine that's allowing the mercury that's sitting up there quite happily in the atmosphere and not affecting anything, to be removed from the atmosphere and interact with the biosphere?  I mean that presumably is a big problem, as you said.  We have our thermometers.  They are sealed.  We don't touch the mercury.  What happens when this mercury gets out of the atmosphere and interacts with the rest of the biosphere?

ROBYN SCHOFIELD
Well, microbes become pretty important, because mercury, through this oxidation process, deposits as a reactive form and then microbes can pick that up and use it and they can methylate it, which means they put on a CH3 group and then we can take it up into our systems.  That crosses the blood brain barrier and that's why it's called a toxin.

SHANE HUNTINGTON
So, given that bromine can so effectively remove mercury from our atmosphere, have we added to the amount of bromine that naturally sits in the atmosphere or the amount of mercury and in either case has that increased our risk, increased our exposure to these toxins?

ROBYN SCHOFIELD
I'll deal with mercury first.  We have doubled the amount of mercury in the atmosphere and so that's significant and we've taken it out of deep deposits and put it into the atmosphere and it stays there - well, it cycles through the biosphere system and we've increased that cycling five times, through doubling it in the atmosphere.

SHANE HUNTINGTON
And presumably, we're continuing to replenish that supply in the atmosphere as well.

ROBYN SCHOFIELD
We are, yes.  So that lifetime of one year that I spoke about, that's how long it will stay in the atmosphere and then it will start going through cycles and it bioaccumulates.  So top of the food chain has high levels of mercury.  Albatross and petrels in the Southern Ocean have the highest levels of mercury in the world.

SHANE HUNTINGTON
And the bromine?

ROBYN SCHOFIELD
Bromine, as I mentioned, is in oceans.  So it's a sea salt and the processes that we were looking at down in Antarctica are really that sea salt bromine.  So through halons, fire extinguishers and using a methyl bromide, it's a really effective fumigant.  It gets potatoes, strawberries, biosecurity, as you are coming in through the airports.  It's really effective.  So we've really increased the amount of bromine containing gases in our atmosphere and these are ozone depleting substances and so the Montreal protocol and it's following amendments have been put in place to stop the production and emission of these species, because they are so effective at destroying ozone.

SHANE HUNTINGTON
How are we going with that?  Are we actually having an impact on reducing those…?

ROBYN SCHOFIELD
Yes.  In the stratosphere, the amount of these bromine containing gases has ceased to increase and chlorine containing substances is decreasing.  So we've done well.

SHANE HUNTINGTON
I'm Shane Huntington and my guest today is Dr Robyn Schofield.  We're talking about measuring mercury and bromine in the Antarctic, here on Up Close.Now, let's move to Antarctica, because that's where your great interest lies.  Now, there is no coal burning in Antarctica.  A lot of the contaminants we're talking about are not produced in Antarctica.  So why are we looking at the atmosphere in Antarctica?

ROBYN SCHOFIELD
It's a pristine environment and it's a check on the health of our atmosphere, down there.

SHANE HUNTINGTON
What sort of things do you measure?  Presumably, your measuring some of these toxins that we're producing in our great cities, in this pristine environment, as you say.

ROBYN SCHOFIELD
During this sea ice physics experiment, we were really targeting this mercury deposition that's been caused by these massive amounts of bromine explosion events.  They're really particular just to the polar spring.  We get sea salt building up on the first year sea ice.  When the sun returns in the polar spring, the suddenly you get massive amounts of highly reactive bromine in the boundary layer.  Now that's the layer between the surface and up to two kilometres and can be as shallow as 200 metres and probably the best example.  Everyone would have seen the boundary layer at some point.You've noticed it's all smoggy in the city and then if you climb up a hill and you are out of it, you are out of the boundary layer.  That's your boundary layer and that is like a little cooking pot of chemistry there.  So you get these massive amounts of really reactive bromine there.  So effective, it destroys all the surface ozone and mercury is in it's elemental form and that's how it stays in the atmosphere for up to a year.  You get that coming, meeting this massive amount of highly reactive bromine and deposits as that reactive form on the surface and then the microbes do their work.  The ocean takes it up.

SHANE HUNTINGTON
And enters our food chain in some way.

ROBYN SCHOFIELD
It enters the food chain.  Some of it returns to the atmosphere and we're trying to work out what actually is going on there.  How much is going into our food chains.  What are the microbes doing?  How are they doing it?  These microbes get exposed to a large amount of this mercury and they have genes to deal with that.  So that's interesting.

SHANE HUNTINGTON
When you have the mercury deposited on the surface in this boundary layer, what is happening at that point?  The bacteria starts taking over and the microbes are involved, what's actually going on in terms of the local biosphere?

ROBYN SCHOFIELD
So, the biosphere at that time.  It's polar spring.  It's starting to ramp up.  You are getting algae forming at the bottom of the sea-ice.  Krill start eating that.  So it's a really active time for the Antarctica biosphere and so you're getting this large amount of mercury being deposited, being bio available and it is being taken up into the food chain. And as I mentioned, petrels and albatrosses and sea birds in the Southern Ocean have really high, highest in the world, mercury levels.

SHANE HUNTINGTON
Do we have an idea of how much we're changing those levels? Did they always have these high levels or are we seeing the impact of our activities in some of these species?

ROBYN SCHOFIELD
This is a really poorly studied problem and I think we can't answer that question right now.  We need to do the biology and really sampling mercury in these higher forms of life down in the Antarctic region.

SHANE HUNTINGTON
It sort of makes sense though, doesn't it, I suppose if we're doubling some of these values, that we would see it throughout the food chain.  It's got to go somewhere.

ROBYN SCHOFIELD
Yes.  The five times more cycling we are seeing will have an impact.

SHANE HUNTINGTON
When we think about the body of work that you are doing, I mean there is some great answers coming out here about what's going on with the atmosphere and how far the impact of our options is having an effect.  Most people wouldn't think the Antarctic region is being damaged by what our local power production is doing.  What does that mean in terms of changing people's behaviour?  I mean, what's the message that we have to get out there, in terms of getting people to change their local behaviour of electricity use, energy use and so forth?

ROBYN SCHOFIELD
If you make a choice for renewable energies, you are moving away from using resources that are not capturing this mercury.  It is a financial cost.  In Europe and in the US, if you capture sulphur you will capture the mercury as well.  You get that for free.  So if there is a large enough public voicing of this and putting sulphur traps on power plants, then we will remove the mercury from the atmosphere and have less of an impact.  Most of the mercury, of course, when you have a power plant, will be deposited locally.  It's reactive first and then it's the elemental mercury which will make it into the atmosphere.

SHANE HUNTINGTON
One of the good things here, of course, too is that it's a relatively short cycling period, so if we have a change occurring now, we are talking five to 10 years and we'll see the effect, won't we?  It's not like some of the problems we have with Co2.  This is something we can have an impact on pretty radically.

ROBYN SCHOFIELD
That's right and it's the same if you eat tuna, for example and you have the high mercury levels in your body.  If you stop eating mercury, you can reduce those mercury levels relatively quickly.  So it's the same in the atmosphere.  You stop putting it into the atmosphere.  Volcanoes we can't do much about.  They're still going to put mercury in. And what we can do something about, if we do something in that realm we'll be able to change things.

SHANE HUNTINGTON
Robyn, the expedition down to Antarctica that your research Group has been involved with.  Let's talk a bit about that.  It's quite a long journey down to Antarctica by boat.  Does your team sample the atmosphere all the way down?  I can imagine you'd get quite a profile of the changing atmosphere, as you head towards that pristine space.

ROBYN SCHOFIELD
Yes.  You leave Hobart and then it takes about five to 10 days, depending on the ocean, to get down to the marginal: sea-ice and we're sampling the whole way down there.  We're getting that whole trend set.  With our bromine measurement, it's an optical measurement, so we are only measuring during the day.  If they are making very good time, then we miss chunks of that.  But the mercury and methylated halides ozone, we measured the whole way.  So that's really an interesting dataset.

SHANE HUNTINGTON
Do you see that sort of increase in, I guess, pristine nature of the atmosphere, as you head down and the pollution levels dropping off?  Are there any surprises when you are looking at that dataset?

ROBYN SCHOFIELD
Once you are on the Southern Ocean it's fairly pristine already.  But what you do see, is you see biological activity dropping of a little bit.  You really enter into the background conditions.  But we haven't seen huge changes.  You don't see much influence, certainly not in the mercury and then you reach background levels fairly quickly.

SHANE HUNTINGTON
Now, Antarctica  is often referred to as the last sort of vestige that we haven't destroyed as a continent.  How important is it that we keep it that way?  There has been a lot of controversy over the last three decades, with drilling into Lake Vostok and other similar areas.  How important is it for our understanding of climate and the impact that we have on it and the contaminants in the atmosphere that we keep this area pristine?

ROBYN SCHOFIELD
That is extremely important.  All we've got are climate records.  The best and longest are really found in this environment, because no-one has been there.  You can guarantee that it is pristine and there is not many places in our earth that we can say that about.

SHANE HUNTINGTON
Dr Robyn Schofield, Research Fellow in the Atmospheric and Oceanic Sciences Group at the University of Melbourne's School of Earth Sciences.  Thank you for being our guest today on Up Close and talking with us about the importance of atmospheric research in Antarctica.

ROBYN SCHOFIELD
It's been a pleasure.  Thank you.

SHANE HUNTINGTON
Relevant links, a full transcript and more info on this episode can be found on our website at upclose.unimelb.edu.au.  Up Close is a production of the University of Melbourne Australia.  This episode was recorded on the 18th of December 2012.  Our producers for this episode were Kelvin Param and Eric van Bemmel, Associate producer Dyani Lewis.  Audio engineer Gavin Nebauer.Up Close is created by Eric van Bemmel and Kelvin Param.  I'm Shane Huntington.  Until next time, goodbye.

VOICEOVER
You've been listening to UpClose.  We're also on Twitter and Facebook.  For more info, visit, www. http://upclose.unimelb.edu.au.  Copyright 2013 The University of Melbourne.


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