How pulling frozen mud 'Popsicles' from N.W.T. lakes can help make mining cleaner

Researchers are developing new technology to help mining companies do a better job at cleaning lakes in the North.

New technology will help Indigenous groups understand more about lakes with year-by-year data

Researchers Dr. Andrew Macumber, left, and PhD candidate Braden Gregory measure and photograph a freeze core from Walsh Lake, N.W.T. Researchers are developing a new technology that will help mining companies do a better job at cleaning lakes in the N.W.T. (Tim Patterson/Flickr)

An Ottawa researcher developing new technology to pull up and analyze frozen mud samples from N.W.T. lakes says it will give regulators and mining companies a better tool to do their jobs.

"It's a technology that's going to allow mining companies to ... better plan how they're going to use the area around the lake, and make sure that their work is done sustainably," said Tim Patterson, professor of geology at Carleton University. 

"That'll allow them to do better to protect the aquatic ecosystems." 

Currently, mining companies have to follow strict cleanup protocols when planning to mine in the N.W.T.

The territory's Mine Site Reclamation Policy requires companies to provide detailed "pre-disturbance" conditions as part of their application — and measuring the chemical environment of nearby lake waters and their sediments is a criteria.

That's why it's important to know the natural, baseline metal concentrations in the lakes — so companies know exactly how much to clean the lake of contaminants like arsenic, said Patterson.

But current methods are not good enough, he said.

Regulators ... they have a very powerful tool here.- Scott Cairns, manager at N.W.T. Geological Survey

When a mining company uses current technology — basically regular tubes — to retrieve sediments from lakes, Patterson said the samples become a "soupy" mixture. 

"The flaw with these cores is that when they hit the lake bottom, it tends to stir some of the sediments up ... basically as if you took a mixer and was mixing something to bake a cake."

But Patterson's technology involves something called freeze coring. Researchers would lower a flat-sided, hollow metal tube with dry ice and alcohol inside. 

They drop it into the lake and sink it low into the mud. 

"Then they'd bring up the telephone pole basically," said Patterson. "It's just a Popsicle basically of mud."

This frozen core sample from Walsh Lake, N.W.T., offers up decades of data per millimetre, says Patterson. These kind of cores are 'highly prized' by researchers, as they are an undisturbed record of environmental change that can span thousands of years, says Patterson. (Tim Patterson/Flickr)

He said the frozen core samples offer up decades of data per millimetre. 

"It creates an absolutely perfect record of deposition spanning thousands of years," said Patterson. 

The samples are then transported to Ottawa for studying, and parts of it sent to McMaster University in Hamilton, Ont., where a machine called iTrax is used to scan the layers in high resolution. 

There's only two of those machines in Canada, said Patterson. Currently, researchers can only scan little bits of the core, a few centimetres in length.

The coring site on Walsh Lake in the N.W.T. Researchers will partner with TerraX Minerals to do field research in lakes in the Yellowknife area. (Tim Patterson/Flickr)

The project recently received about $4.5 million in new funding to help develop "containment vessels" for the mud Popsicles to keep frozen longer, while scientists scan its layers using the machine.

We want to hold industries and governments accountable for contamination of our members' traditional land.- Shin Shiga, North Slave Métis Alliance

Researchers hope to scan up to 50 centimetres of sediment without it melting, which would take 25 hours, said Patterson.

His project has been in the works for more than a decade, and researchers are now teaming up with mining company TerraX Minerals to do field research in lakes in the Yellowknife area.

Difference in northern vs. southern lakes

Current technology to gather lake sediments typically works in the South, but not for northern lakes, explained Scott Cairns, a manager with the N.W.T. Geological Survey. The survey is working with Patterson.

A close-up of the top of a freeze core. Patterson says the core shows several distinct environments have existed in this lake in the past. The black bands in the core indicate low oxygen conditions, and the core is currently being analyzed to determine the black lines' significance. (Tim Patterson/Flickr)

"Down south, those [sediment] layers are fairly thick because the lakes there are organically productive in the warmer climate," said Cairns.

"Up here, they're very thin tiny layers. You can equate them to tree rings almost. And it's very difficult to preserve these structures when you're analyzing a lake sediment core unless it's frozen," said Cairns.

Cairns said Patterson's technology will help give "excellent" high-resolution data, as well as insight into how metals in lakes can move around over time and with climate change.

"It gives us a tool to do the science, so that we understand how to monitor and protect the environment better," said Cairns.

"Similarly, for regulators who are trying to understand if the [mining company] is doing the job properly, they have a very powerful tool here."

Patterson said his technology is cost-effective, and hopes to have companies using it by 2022.

Data important for Indigenous group

An official with the North Slave Métis Alliance said this research is important in order to inform Indigenous groups with reliable information about the environment.

"We want to hold industries and governments accountable for contamination of our members' traditional land," said Shin Shiga, manager of the environment department with the North Slave Métis Alliance. The group is supporting Patterson's program by offering staff time and elders' knowledge.

Shiga said he wants members to be "well-informed" about the natural background condition of the land they've lived on for hundreds of years.

"And sometimes the background natural metal levels are elevated. So if that's the case, I want people to know."


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