A toxic journey from Europe to the far North
Scientists dig “huge white cigars” in the ice to track dangerous metals
Next month, as the sun reappears in the High Arctic and temperatures rise, particles of potentially toxic metals, carried by hazy, contaminant-filled air from northern Europe and Asia, will filter down on to the ice.
That’s when Jiancheng (James) Zheng, a scientist with the Geological Survey of Canada, heads to Devon Island in Nunavut”s High Arctic, where he and his team spend weeks retrieving ice cores for analysis.
On top of a glacier, 1,800 metres above sea level, Zheng carefully digs a five-metre snow pit by hand, following stringent precautions to avoid any contamination. To take samples of older material from deeper snow and ice layers, Zheng drills a 65-metre long ice core using special equipment made of titanium.
“Once we retrieve the core, we need to seal it into our packing material to protect it from contamination,” Zheng says.
These ice cores, which look a lot like huge white cigars, are carefully stored in plastic containers. Then, the trick is to keep them frozen until they can be studied.
Last year, Zheng brought back hundreds of samples, representing 160 years of snow accumulation. By counting the cores’ layers and analyzing these cores, scientists can track trends over many years.
More than 500 age-dated cores taken by Zheng end up at the University of Heidelberg in Germany, in a unique lab with specialized facilities, where chemist Michael Krachler measures trace metals down to concentrations lower than any other laboratory in the world. To judge recent trends, 45 of the cores came from Zheng’s hand-dug pit, which has accumulated five metres of snow in the past 10 years.
The aim of this joint Canadian-German project is to monitor contaminants and inform authorities — and the public — when this research reveals increased pollutants. Recently, the two scientists reported, in scientific journals, the results of their work on levels of lead and antimony found in ice cores from Devon Island.
Their recent article, published in the Geophysical Research Letters journal, notes that lead concentrations have dropped by 80 per cent since the 1970s, but there is an “overwhelming supply” of industrial lead in the Arctic.
Lead can be harmful even in small amounts, and if it builds up it can cause health problems including nervous system damage and even death.
“Everyone thinks the lead story is over because lead was banned in gasoline in most industrialized countries, but still today 95 per cent of lead we find in the Arctic is from man-made sources. We have started to reduce from a high level, but there are still many, many other sources,” Krachler says. “The ban of the leaded gasoline has had a pronounced effect. It’s good, but not enough. That’s the point.”
Analyses have also found levels of antimony. Antimony is more of a mystery than lead, says Krachler, but it’s also a suspected carcinogen.
Like lead, antimony is a metal, and its main applications are industrial — it’s used in alloys for hardening lead (for example, in batteries and bullets) and in flame-retardants for plastics. Antimony is released by burning plastic. Even state-of-the-art incineration plants are unable catch the tiny antimony particles that float through screening systems.
Recently, attention has been drawn to antimony’s possible role in sudden infant death syndrome. Exposure to high levels of antimony for short periods of time is known to cause nausea, vomiting, and diarrhea and to cause damage to the kidneys, liver, and heart.
Krachler says ice cores from the Arctic now show levels about 50 times more than what is found naturally and that more than 95 per cent comes from man-made sources.
“At the end of the day, everyone wants to know if it’s toxic or not; if it’s not toxic, who cares,” Krachler says. “Some say it’s 10 times more toxic than lead. If that’s true, it would certainly have a toxic effect. The United States Environmental Protection Agency and the European Commission list antimony and compounds as ‘priority compounds,’ so they know something is wrong.”
Zheng won’t be going to Devon Island this spring, but his team will return to update the cores. In the future, he and Kachler would like to look at cores from other places in the High Arctic regions of the world to see whether they find the same levels of contaminants there.
“That’s always the danger when you have one place in the entire Arctic, how representative are your results. We want to check out how representative Devon Island is of the entire Arctic,” Krachler says.
But one thing is sure: this spring will once again see uncomfortable levels of contaminants deposited in the High Arctic islands of Nunavut.