Understanding the mobility and toxicity of selenium

Partnering to assess effectiveness of passive remediation techniques

November 2023

Selenium is an element that occurs naturally in soil and rock. Trace amounts are essential for metabolism in animals, including humans. In high concentrations, however, selenium has the potential to be toxic to wildlife, especially fish, waterfowl, and amphibians. 

Since 2010 Lorax Environmental Services Ltd -- an environmental consultancy based in Vancouver -- has been working with the Industry Services group at the Canadian Light Source (CLS) to better understand processes governing the release of selenium from mine wastes as well as the behaviour of selenium in the environment. “Through our work with the CLS, we have developed a better understanding of the nature of selenium in source rocks, as well as the fate of selenium after it enters aquatic environments,” says Alan Martin, a biochemist and principal with the consulting firm.

Who is Lorax?

Formed in 1996, Lorax specializes in mine-related environmental assessments. Their expertise includes geochemistry, contaminant transport via surface and groundwater systems, and assessing potential impacts to creeks, lakes, and oceans. Lorax’s clients include mining companies, regulatory agencies, and NGOs (non-government organizations). The firm also collaborates with universities across Canada on mining-related environmental research.

In addition to studying the environmental impacts of selenium, Lorax also relies on the CLS Industry Services group to help assess the effectiveness of efforts by mining companies to remove this element from water contaminated by mining. Given the massive price tag to build facilities for actively treating waste water, mining companies are increasingly exploring passive technologies for remediation, including using microbes to take selenium out of solution. “The data we get from the CLS help us to develop the mechanistic understanding of how selenium behaves in these passive treatment systems,” says Martin.

How the nature of collaboration has evolved

Where Lorax initially relied on the CLS to study the fate of selenium in wetlands influenced by mining, more recently the consultancy has been using synchrotron-based techniques to analyze the properties of selenium in suspended particles in effluent released from mines. The consultants capture those particles on filters, which they ship to the Light Source for analysis.

“Different forms of selenium have different levels of bioavailability,” explains Martin. “Understanding the forms of selenium present in suspended particles can help us better evaluate selenium transport and the potential risks to aquatic systems.”

Martin says working with the CLS enables Lorax to apply a weight of evidence approach to studying selenium, from its sources in mine rock, through water treatment, and in various aquatic environments. “We can use the data from the CLS to better understand the solid phase properties of selenium that form in treatment systems and downstream environments,” he says “as well as the potential for selenium to re-enter the environment”.

“Overall, there's this nice upstream to downstream application (by using the CLS) where we can look at these different compartments that collectively inform how we understand selenium remobilization, treatment and environmental risk,” says Martin.