Environmental planning research informs the management of human activities on the land and management of resources to preserve ecological integrity and ensure sustainability. The development of hazard maps for risks and vulnerabilities, and studies on the impacts of tourism play critical roles in underpinning effective planning approaches throughout the Northwest Territories (NWT).
Rare earth elements (REEs) are considered “data poor” when it comes to understanding their geochemistry in surface waters and the links between this chemistry and their potential toxicity to aquatic organisms. The least understood aspect of REEs is their complexation by dissolved organic matter; this complexation can mitigate their toxicity and quantifying this binding is necessary to properly assess risk in for receiving waters containing organic matter, such as in the NWT. The current state of the art in metal-organic matter complexation predictions is the Windermere Humic Aqueous Model (WHAM). To run this model, binding constants must be determined – so-called logK values. Our project involves measuring these logK values for diverse organic matter sources and comparing them to default WHAM values. We have found that the WHAM parameters overestimate binding by many orders of magnitude at low REE concentrations. Our work will help refine this geochemical tool so it can appropriately be utilized for risk assessment of potential future REE mining operations in the NWT.
Researcher: Seana Brennan, MSc (2016–present)
Rare earth elements (REE) tend to occur in water as trivalent cations, and like other trivalent species, such as aluminum and iron, they are often of low solubility in surface waters. This low solubility makes performing toxicity assays very difficult, both in terms of doing the actual test and also in interpreting the resultant data. These toxicity assays are essential to establish safe limits of REE in surface waters of the NWT. Geochemical tools exist to predict solubility of elements for given water chemistry but the parameter values (Ksp values) that determine solubility of rare earth elements are uncertain by two orders of magnitude in standard databases. My research involves detailed and systematic variation of water chemistry parameters and measuring the impact on REE solubility. The result will be improved precision and accuracy on Ksp values for REEs and an ability to better interpret toxicity assay results, and ultimately result in improved predictions of REE impacts in surface waters of the NWT.
Researcher: Leah Mindorff, BSc Honours (2018–present)
Dissolved organic matter (DOM) can bind metals and reduce their bioavailability and toxicity. This is relevant to areas in the Northwest Territories that have experienced metal contamination from mining activities. While DOM quantity is known to influence toxicity, less is known about the role DOM quality plays. To better understand the unique qualities of northern DOMs, I am studying samples collected from lakes around Yellowknife. My goal is to identify the chemical components and the metal binding characteristics of these samples. Understanding the relationships between chemical makeup and metal binding affinity will support the incorporation of DOM quality into toxicity prediction models. This work will contribute to improved environmental impact assessment in northern ecosystems and provide managers with relevant models that account for site-specific differences.
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