NWT RESEARCH DATABASE

Tags: water quality, arsenic, climate change, metals, cumulative effects

Objective(s): To assess the present-day and future stability of legacy arsenic contamination stored in Yellowknife Bay sediments that originated from local gold mining activities.

Project Description: This study will assess the present-day and future stability of legacy arsenic contamination stored in Yellowknife Bay sediments that originated from local gold mining activities. Using a combination of quantitative methods (field measurements, laboratory experiments, paleolimnology and mass balance modelling), the research team will estimate the diffusion of arsenic from sediments to overlying water in the bay, investigate environmental factors that control this process, and develop predictions of how long-term environmental change from climate warming during the 21st century could impact arsenic cycling and levels of water arsenic in Yellowknife Bay. This project will generate information for community organizations and decision makers who are involved in the environmental management of this important waterbody for residents of Ndilo, Detah, and Yellowknife. To evaluate the long-term stability of arsenic contamination in Yellowknife Bay sediments and the potential for increased arsenic diffusion from sediments, the team will: 1) measure current levels of arsenic diffusion from sediment to overlying water; 2) characterize arsenic mineralogy in sediment to assess its origin and stability; 3) conduct lab experiments to estimate future rates of arsenic diffusion to overlying water due to environmental change (warmer temperature, reduced sediment oxygen); 4) characterize environmental change in Yellowknife Bay that has already occurred over the last century as a result of warming (using paleolimnology techniques); and 5) develop a model to predict changes in water arsenic concentrations of Yellowknife Bay during the 21st century. The field-based components of this project will involve the collection of sediment cores for chemical measurements on sediment (solid-phase) and porewater, as well as the collection of surface water for chemical analysis. The Yellowknives Dene First Nation (YKDFN) is concerned about the environmental impacts of arsenic pollution in Yellowknife Bay. The bay is a waterbody of cultural, subsistence and recreational importance for the two YKDFN communities located on its shores. Previous environmental research on Yellowknife Bay from 2013 to 2015 involved collaboration with the YKDFN and their specific concerns were incorporated into that study design. This new study has been developed in collaboration with YKDFN team members, who will be involved in the project design and implementation. A YKDFN guide will assist for boat-based sampling on Yellowknife Bay (summer of 2018 and 2019), and a YKDFN field assistant for the collection of environmental samples. Government and community organizations were contacted to discuss the project proposal, and on-going communication will allow for opportunities to provide feedback during implementation of the study. A project report will be prepared for the Northwest Territories Cumulative Impacts Monitoring Program (final report - April 2020) will be uploaded to the NWT Discovery Portal. Annual meetings with community organizations and decision makers in Yellowknife in the fall of 2018 and 2019. An oral will be presented annually at the Yellowknife Geoscience Forum (2018, 2019). Water chemistry data will be uploaded to the Mackenzie Datastream at the project end (2020). A technical report to communicate main findings at the end of the project (in 2020-21), distributed in an open-data format. An NWT Environmental Research Bulletin will be created to communicate plain-language results (2020). The fieldwork for this study will be conducted from July 25, 2018 to August 20, 2018.