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Throwing out the garbage, Antarctica-style
Technology
Throwing out the garbage, Antarctica-style How do you get rid of pollution and waste when it is frozen solid for most of the year? EMMA YOUNG, SYDNEY
BATTERIES, diesel, oil drums and dead dogs. These are just a few of the items that have been dumped in makeshift rubbish tips in Antarctica. Decades of exploration and research have left more than 70 waste sites spread along the coast of the continent on ice-free rocky outcrops, which also happen to be home to most of Antarctica’s wildlife. Under the 1991 Madrid protocol, the countries responsible for these waste sites must clean them up, yet progress has been painfully slow. This is largely down to the high cost of working in the inaccessible Antarctic, where removing just 1 tonne of contaminated ground costs $4000, compared with $400 in Alaska. There are also serious technical difficulties. The waste is locked up in ice for much of the year, making it almost impossible to dig out. When the thaw does arrive, meltwater can carry pollution into lakes and the ocean just when animals in the region are beginning to reproduce. This makes digging up sites during the thaw risky, as disturbing the ground can cause even more pollution to be flushed into the ocean (New Scientist, 6 October 2001, p 16). What’s 28 | NewScientist | 25 November 2006
061125_N_Tech DPS 28
more, traditional technologies used to prevent this run-off while the rubbish is removed – or render pollutants harmless so that they can be left in the ground – are rendered useless by the freezing conditions. Cleaning up the continent could be about to get much easier, however, with the help of new techniques currently being tested in Antarctica and in laboratories elsewhere. For some sites with large amounts of solid waste such as fuel drums and batteries, removal is the only real option. Other sites, such as those contaminated with fuel or heavy metals, might be contained and treated on site at a fraction of the cost. At Australia’s Casey research station on the east coast of Antarctica, for example, there has been a series of diesel spills, including an incident in 1999 when 5000 litres was discharged. That diesel is now seeping into a lake that empties into the ocean, so containing it is Australia’s highest remediation priority. A team led by Ian Snape of the Australian Government Antarctic Division in Kingston, Tasmania, is working on a new technique they hope could solve the problem. If successful, the team, which is collaborating with Geoff Stevens at the University of Melbourne and Damian Gore, a
physical geographer at Macquarie University in Sydney, believe it will give a much needed boost to international clean-up efforts. “If we can develop cheap, effective in situ techniques, it might encourage other countries to do more,” Snape says. In temperate climates, the most effective way to remove pollutants from groundwater is to use a permeable reactive membrane. These barriers contain materials that adsorb the pollutants or transform them into harmless substances. However, their absorbency means they generally hold a lot of water, and in Antarctic conditions that means they are likely to freeze solid. They then take longer than the surrounding soil to thaw in spring, rendering them useless just as the polluted meltwater begins to flow. “They effectively become a big plug, as water just flows around or over them,” says Snape. To add to the problem, the fact that water expands as it forms ice crystals means the material is often left full of holes, Stevens says. “It’s like someone comes along and drills a hole through your barrier.” To get around these problems, the team has been experimenting with barriers containing reactive granules of different sizes. One
problem with conventional barriers is that granules less than 200 micrometres across can become clogged with “biofilm” created when bacteria form communities on the surface. This hinders water flow through the barrier, helping it to become waterlogged and freeze. The goal is to find a granule size small enough to retain a high surface area for adsorbing pollutants, but large enough to allow water to flow freely. The team is currently experimenting with granules ranging from 0.4 to 2 millimetres across. Last December, the researchers installed a prototype barrier in the ground at Casey by digging a trench 5.5 metres long, 2 metres wide and 1 metre deep across the path of the polluted meltwater. They built wings on either side to funnel the water towards the trench, which was then filled with a barrier consisting of three layers of permeable, reactive materials. The first layer uses zeolites to release nitrogen into the water. Zeolites are aluminosilicate compounds with a porous, honeycomb structure. Before installation, the zeolite is washed in a concentrated ammonium chloride solution to loosely bind positively charged ammonium ions to its porous surface. As the
SLAMMED IN THE COOLER What do you do with a former gold mine packed with 237,000 tonnes of arsenic-contaminated dust? Deep freeze it, say the team responsible for Canada’s Giant Mine near the city of Yellowknife in the Northwest Territories. In 1999, the government department Indian and Northern Affairs Canada took responsibility for the toxic arsenic trioxide created as a by-product of gold extraction at the mine, stored in 15 underground chambers. After considering more than 50 options, deep-freezing the dust and the surrounding rock to isolate it from the surrounding environment emerged as the best solution, says Bill Mitchell, head of the project. A plan is about to
be submitted for regulatory approval, and the process could begin in the next two years. The chambers will be slowly frozen using a supercooled liquid passed through underground pipes connected to a freezer on the surface. Thermosyphons, which require no electricity to run, will then be used to keep the site frozen. These consist of a sealed tube, the base of which is buried in the frozen rock. Heat from the surroundings vaporises pressurised liquid carbon dioxide at the bottom of the tube, causing it to rise to the top where it releases the heat through radiator fins. The cooled carbon dioxide then condenses into a liquid and dribbles back down. www.newscientist.com
20/11/06 11:40:33 am
AUSTRALIAN GOVERNMENT ANTARCTIC DIVISION
–Easy to make a mess, harder to clean it up–
immobilises metal in the soil and prevents it being leached out. The soil can then be safely buried in landfill. “We want to know: would that work if we tried it in Antarctica?” Snape says. team arrived at the site to begin “Would the freeze-thaw process analysing hydrocarbon levels in water that has passed through destabilise the binding? And could we find a way just to inject the barrier. The initial results that orthophosphate solution, are expected in the next few without having to dig the polluted weeks, and if the barriers prove soil up? That would be a huge successful they could be used cost saving.” at four other Australian sites in It is not just Antarctica that the Antarctic. could benefit from this research. This season, researchers will The team hopes the methods also collect soil samples from could also be applied in the Arctic, three waste sites for research particularly across the countries into new ways to deal with heavy metal pollution caused by of the former Soviet Union, where Snape describes the amount of dumped batteries, construction waste and abandoned mechanical contamination as “staggering”. The size of the problem means parts. Copper, lead, nickel, low-cost remediation zinc and cadmium are the technologies are essential. main culprits. In Australia, soil In North America, BP contaminated with heavy Exploration Alaska has agreed metals is churned with an to provide funding for further orthophosphate solution, which
“Decades of exploration and research have left more than 70 waste sites in Antarctica” meltwater washes over the zeolite, native bacteria pick up the ammonium ions and use them to metabolise hydrocarbon pollutants. To trap the hydrocarbons long enough for bacteria to break them down, the second layer contains granules of activated carbon, a dry, porous material with a large surface area. The final layer contains another zeolite, this time activated to take nutrients back out of the water by swapping its positively charged sodium ions for excess ammonium in the water. This prevents a plume of nitrogen-rich water moving downstream and causing an algal bloom that would kill fish and other aquatic life. Last month a three-person www.newscientist.com
061125_N_Tech DPS.indd 29
development of the barrier concept, in the hope of using the technology to contain any spills from its petroleum exploration sites. Meanwhile in Canada, though the government committed CAN$3.5 billion (US$3 billion) in 2004 to the clean-up of federal contaminated land and innovative techniques for in situ stabilisation are being developed (see “Slammed in the cooler”), there is also an urgent need for effective ways to clean up former mining areas. In situ treatment is about being realistic, says Snape. “In Antarctica, we’d all like to see it pristine again with no contamination, but for many sites that is just not going to be achievable. A far better thing is to manage these sites in a practical way. Let’s control it and make sure there are no further impacts, and let the environments recover. That’s our goal.” ● 25 November 2006 | NewScientist | 29
20/11/06 5:48:21 pm
Throwing out the garbage, Antarctica-style How do you get rid of pollution and waste when it is frozen solid for most of the year? EMMA YOUNG, SYDNEY
BATTERIES, diesel, oil drums and dead dogs. These are just a few of the items that have been dumped in makeshift rubbish tips in Antarctica. Decades of exploration and research have left more than 70 waste sites spread along the coast of the continent on ice-free rocky outcrops, which also happen to be home to most of Antarctica’s wildlife. Under the 1991 Madrid protocol, the countries responsible for these waste sites must clean them up, yet progress has been painfully slow. This is largely down to the high cost of working in the inaccessible Antarctic, where removing just 1 tonne of contaminated ground costs $4000, compared with $400 in Alaska. There are also serious technical difficulties. The waste is locked up in ice for much of the year, making it almost impossible to dig out. When the thaw does arrive, meltwater can carry pollution into lakes and the ocean just when animals in the region are beginning to reproduce. This makes digging up sites during the thaw risky, as disturbing the ground can cause even more pollution to be flushed into the ocean (New Scientist, 6 October 2001, p 16). What’s 28 | NewScientist | 25 November 2006
061125_N_Tech DPS 28
more, traditional technologies used to prevent this run-off while the rubbish is removed – or render pollutants harmless so that they can be left in the ground – are rendered useless by the freezing conditions. Cleaning up the continent could be about to get much easier, however, with the help of new techniques currently being tested in Antarctica and in laboratories elsewhere. For some sites with large amounts of solid waste such as fuel drums and batteries, removal is the only real option. Other sites, such as those contaminated with fuel or heavy metals, might be contained and treated on site at a fraction of the cost. At Australia’s Casey research station on the east coast of Antarctica, for example, there has been a series of diesel spills, including an incident in 1999 when 5000 litres was discharged. That diesel is now seeping into a lake that empties into the ocean, so containing it is Australia’s highest remediation priority. A team led by Ian Snape of the Australian Government Antarctic Division in Kingston, Tasmania, is working on a new technique they hope could solve the problem. If successful, the team, which is collaborating with Geoff Stevens at the University of Melbourne and Damian Gore, a
physical geographer at Macquarie University in Sydney, believe it will give a much needed boost to international clean-up efforts. “If we can develop cheap, effective in situ techniques, it might encourage other countries to do more,” Snape says. In temperate climates, the most effective way to remove pollutants from groundwater is to use a permeable reactive membrane. These barriers contain materials that adsorb the pollutants or transform them into harmless substances. However, their absorbency means they generally hold a lot of water, and in Antarctic conditions that means they are likely to freeze solid. They then take longer than the surrounding soil to thaw in spring, rendering them useless just as the polluted meltwater begins to flow. “They effectively become a big plug, as water just flows around or over them,” says Snape. To add to the problem, the fact that water expands as it forms ice crystals means the material is often left full of holes, Stevens says. “It’s like someone comes along and drills a hole through your barrier.” To get around these problems, the team has been experimenting with barriers containing reactive granules of different sizes. One
problem with conventional barriers is that granules less than 200 micrometres across can become clogged with “biofilm” created when bacteria form communities on the surface. This hinders water flow through the barrier, helping it to become waterlogged and freeze. The goal is to find a granule size small enough to retain a high surface area for adsorbing pollutants, but large enough to allow water to flow freely. The team is currently experimenting with granules ranging from 0.4 to 2 millimetres across. Last December, the researchers installed a prototype barrier in the ground at Casey by digging a trench 5.5 metres long, 2 metres wide and 1 metre deep across the path of the polluted meltwater. They built wings on either side to funnel the water towards the trench, which was then filled with a barrier consisting of three layers of permeable, reactive materials. The first layer uses zeolites to release nitrogen into the water. Zeolites are aluminosilicate compounds with a porous, honeycomb structure. Before installation, the zeolite is washed in a concentrated ammonium chloride solution to loosely bind positively charged ammonium ions to its porous surface. As the
SLAMMED IN THE COOLER What do you do with a former gold mine packed with 237,000 tonnes of arsenic-contaminated dust? Deep freeze it, say the team responsible for Canada’s Giant Mine near the city of Yellowknife in the Northwest Territories. In 1999, the government department Indian and Northern Affairs Canada took responsibility for the toxic arsenic trioxide created as a by-product of gold extraction at the mine, stored in 15 underground chambers. After considering more than 50 options, deep-freezing the dust and the surrounding rock to isolate it from the surrounding environment emerged as the best solution, says Bill Mitchell, head of the project. A plan is about to
be submitted for regulatory approval, and the process could begin in the next two years. The chambers will be slowly frozen using a supercooled liquid passed through underground pipes connected to a freezer on the surface. Thermosyphons, which require no electricity to run, will then be used to keep the site frozen. These consist of a sealed tube, the base of which is buried in the frozen rock. Heat from the surroundings vaporises pressurised liquid carbon dioxide at the bottom of the tube, causing it to rise to the top where it releases the heat through radiator fins. The cooled carbon dioxide then condenses into a liquid and dribbles back down. www.newscientist.com
20/11/06 11:40:33 am
AUSTRALIAN GOVERNMENT ANTARCTIC DIVISION
–Easy to make a mess, harder to clean it up–
immobilises metal in the soil and prevents it being leached out. The soil can then be safely buried in landfill. “We want to know: would that work if we tried it in Antarctica?” Snape says. team arrived at the site to begin “Would the freeze-thaw process analysing hydrocarbon levels in water that has passed through destabilise the binding? And could we find a way just to inject the barrier. The initial results that orthophosphate solution, are expected in the next few without having to dig the polluted weeks, and if the barriers prove soil up? That would be a huge successful they could be used cost saving.” at four other Australian sites in It is not just Antarctica that the Antarctic. could benefit from this research. This season, researchers will The team hopes the methods also collect soil samples from could also be applied in the Arctic, three waste sites for research particularly across the countries into new ways to deal with heavy metal pollution caused by of the former Soviet Union, where Snape describes the amount of dumped batteries, construction waste and abandoned mechanical contamination as “staggering”. The size of the problem means parts. Copper, lead, nickel, low-cost remediation zinc and cadmium are the technologies are essential. main culprits. In Australia, soil In North America, BP contaminated with heavy Exploration Alaska has agreed metals is churned with an to provide funding for further orthophosphate solution, which
“Decades of exploration and research have left more than 70 waste sites in Antarctica” meltwater washes over the zeolite, native bacteria pick up the ammonium ions and use them to metabolise hydrocarbon pollutants. To trap the hydrocarbons long enough for bacteria to break them down, the second layer contains granules of activated carbon, a dry, porous material with a large surface area. The final layer contains another zeolite, this time activated to take nutrients back out of the water by swapping its positively charged sodium ions for excess ammonium in the water. This prevents a plume of nitrogen-rich water moving downstream and causing an algal bloom that would kill fish and other aquatic life. Last month a three-person www.newscientist.com
061125_N_Tech DPS.indd 29
development of the barrier concept, in the hope of using the technology to contain any spills from its petroleum exploration sites. Meanwhile in Canada, though the government committed CAN$3.5 billion (US$3 billion) in 2004 to the clean-up of federal contaminated land and innovative techniques for in situ stabilisation are being developed (see “Slammed in the cooler”), there is also an urgent need for effective ways to clean up former mining areas. In situ treatment is about being realistic, says Snape. “In Antarctica, we’d all like to see it pristine again with no contamination, but for many sites that is just not going to be achievable. A far better thing is to manage these sites in a practical way. Let’s control it and make sure there are no further impacts, and let the environments recover. That’s our goal.” ● 25 November 2006 | NewScientist | 29
20/11/06 5:48:21 pm