Improved monitoring of mine remediation: selenium isotopes are a good indicator of cleanup operations

A new testing technique developed using synchrotron light could significantly improve the way we monitor the effectiveness of remediation practices to remove selenium contamination from mining activities.

Selenium is a naturally occurring nutrient that humans and animals need in small amounts to maintain good health. However, exposure to higher concentrations can cause neurological problems in humans and death and infertility in wild animals and cattle.

Mining releases selenium and other substances into nearby soils and water bodies, which can accumulate over time even when mitigation strategies such as constructed wetlands and selenium-removal bacteria are in place.

“Mining is necessary to get certain resources out of the ground,” says Heather Shrimpton, a postdoctoral researcher in the School of Earth and Environmental Sciences at the University of Waterloo. “We still cannot rely 100% on recycled materials, so it is important to have technologies that can reduce the impact that mining has on people and the environment, and my technology can help with that. ”

Until now, there was no way to determine whether selenium might be permanently lost as a result of restoration efforts, or whether it was being absorbed into nearby streams and riverbanks.

Shrimpton and colleagues discovered that selenium isotopes (the same element as selenium but with a different atomic weight) can be used to identify what is removing this pollutant from water. Isotopic changes indicate whether selenium is being removed and whether that removal is permanent. Shrimpton’s research is published in the journal Environment Science and Technology.

“We need technology like mine to make sure the cleanup system is working, to test if it needs to be better,” Shrimpton said. .

In the lab, Shrimpton and her team recreated a well-known remediation strategy called reduction, which uses sulfur-reducing bacteria to capture selenium in solid form. In nature, reduction causes selenium to adhere to gravel and sand in bodies of water.

Using the Canada Light Source (CLS) at the University of Saskatchewan (USask), Shrimpton analyzed the isotopes of these solid selenium samples. She found that adding a certain amount of sulfur to selenium prevented the contaminant from remixing with the liquid, which could make its removal from the water permanent. The extent of the isotopic change confirmed that the reduction process was the only cause of the change, she says.

“With the Canadian light source, we’re able to collect additional information on a molecular scale so we can see what’s going on and say, ‘This is the cause, this is the cause.'” Shrimpton said. “It’s one piece of the puzzle.”

Now that the technology has proven effective in the lab, Shrimpton and her team plan to test it at mine sites and expand their research to include other mine environment contaminants, such as mercury. is.