Various methods, such as using bacteria, can remove elements like selenium from water; a new test using specialized light verifies the effectiveness of these solutions.

Heather Shrimpton, a postdoctoral fellow in the Department of Earth and Environmental Sciences at the University of Waterloo, and her team are on the hunt for selenium, a naturally occurring nutrient with a nasty habit of causing neurological problems, infertility, and death at higher concentrations.

Selenium and other substances can be released into runoff during the mining process, contaminating nearby soil and water bodies despite mitigation strategies such as manufactured wetlands or selenium-removing bacteria being put in place.

Until now, there has been no way to determine whether selenium is dissipating as intended during remediation efforts or whether it is simply being absorbed in nearby creeks or riverbanks.

"We need a technique like mine to check if cleanup systems are working – it's to test to see whether or not we need to do better," said Shrimpton.

Understanding that, at least for now, mining is necessary to provide the minerals for technological innovation and everyday living, environmental scientists want to make sure that efforts to minimize harmful impacts are working.

"We can't just rely 100% on recycled materials yet," she added. "So, it's important that we have techniques that can lessen the impacts that mining has on people and the environment, and my technique can help with that."

The best way to find selenium? More selenium.

Shrimpton and colleagues discovered that variations in selenium isotopes, which have different atomic masses, can reveal exactly what is removing this contaminant from the water while also signaling whether the removal is effective and permanent.

A well-known remediation strategy called reduction, which uses sulfur-reducing bacteria to trap selenium in a solid form, was replicated in the lab by Shrimpton and her team. In nature, this process causes selenium to adhere to gravel and sand in water bodies.

Using the Canadian Light Source (CLS) at the University of Saskatchewan, Shrimpton analyzed the isotopes of these solid selenium samples with synchrotron light. She found that adding specific amounts of sulfur to selenium prevents the contaminant from mixing with liquids again, confirming through observed changes in the isotopes that the reduction process alone was successful, making the removal from water potentially permanent.

"The Canadian Light Source let me gather extra information on the molecular scale, so I knew what was happening," said Shrimpton, now able to determine successful remediation processes without a doubt. "It's one piece in solving the puzzle."

The CLS is the only synchrotron in Canada and one of the largest scientific infrastructure investments in the country's history, enabling science, learning, and socio-economic benefits through the provision of synchrotron light.

With the technique proven effective in the lab, Shrimpton and her team plan to test it at mine sites and expand their study to include other elusive environmental mining pollutants, such as mercury.

Shrimpton's study is published in the journal Environmental Science and Technology.