The melting Arctic permafrost is unleashing a 'toxic' legacy

An abandoned gold mine in Canada is known as a "sleeping monster" by Indigenous locals – because it contains enough arsenic to kill 1.7 trillion people.

Giant Mine, near the subarctic city of Yellowknife, was once one of the biggest gold mines in the Northwest Territories, said The Wall Street Journal. The "unwanted by-product" of five decades of mining is 237 tonnes of arsenic trioxide "locked in the subterranean caverns". Just 140 milligrams is enough to kill a person.

After it closed in 2004, Yellowknife's 20,000 inhabitants hoped the poison would "remain frozen underground forever". But mining and climate change have caused the permafrost to melt, raising fears that the arsenic could "slither into" a nearby freshwater lake, "snake" along a river and enter the Arctic Ocean, "poisoning the wildlife, the land and the water along its path". And Giant Mine is not the only example of melting permafrost unleashing potentially poisonous chemicals. It is, according to environmentalists, a "warning" for those who "want to mine the riches of the North".

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'Highly concerning'

People picture the Arctic as a "harsh wilderness of endless tundra criss-crossed by rivers of crystal-clear water and home to wildlife untouched by humans", said the Worldwide Fund for Nature. But this "picturesque image masks a stark reality": the industrial exploitation of the mineral-rich Arctic permafrost regions.

There are tens of thousands of contaminated sites, ranging from "micro-dumps full of toxic sludge from oil and gas exploration to abandoned military installations to stockpiles of mining debris".

Operators "assumed that the permafrost would reliably and permanently seal off" the substances underground. In many cases, they did not "make adequate disposal efforts". Now, the permafrost is thawing as the earth warms, and it's threatening to potentially unleash many of these toxic substances into the environment.

Bear in mind that the Arctic is "warming four times faster than the rest of the world", said CNN. In Alaska, some rivers are already changing from "clean, clear blue to a rusty orange", due to the run-off of "toxic metals" released by the permafrost, including iron, zinc, copper, nickel and lead, which had been "locked away underground".

While some high concentrations of toxic materials are down to mining, large amounts of these metals also occur naturally in the permafrost. That includes mercury, with scientists finding "highly concerning" levels in melted permafrost, said High Country News. When mercury is ingested it can "wreak havoc on the neurological system", especially for pregnant women and children.

"Permafrost soil contains more mercury than all the other soil on the planet, plus all the oceans, plus the atmosphere,” said Josh West, study co-author. In that sense, he said, it's like a "bomb that's going to go off".

'Toxic forever'

Donald Trump's threats to take control of Greenland and annex Canada have intensified the "cold rush", said the WSJ. Miners are rushing to claim the valuable rare-earth materials buried under the permafrost, needed for smartphones and EV batteries.

But that comes with "high, and enduring, risks and costs". Estimates for the clean-up of Giant Mine reach $3.2 billion (£2.4 billion): one of the most expensive mine remediations in Canada's history. And it is a "perpetual care" project: Canada must maintain it for at least 100 years. "Some local activists and environmental scientists fear the danger will lurk forever."

The Arctic is "dotted" with such long-term operations. Canada's government estimates that there are 24,000 in the country. Last year another mine in the Yukon "spilled an avalanche of zinc and cyanide into the landscape and nearby waterways".

At Giant Mine crews have "demolished" arsenic-contaminated equipment, "stabilised" the mine and will soon start building a water-treatment plant. There is also a plan to drill metal tubes into the ground and use carbon dioxide to draw heat out and "funnel cold gas back in", freezing the arsenic in blocks of ice that would take years to thaw.

The government believes freezing is "the most efficient and least expensive way to deal with the arsenic". But many say the plan "isn't good enough" in the long term. Arsenic doesn't degrade: the mine will "be toxic forever". The elders of the Indigenous people of the area call Giant Mine "Nahga": the monster.