NWT RESEARCH DATABASE

Tags: contaminants, mercury, water quality

Objective(s): To identify and quantify the different possible sources of toxic mercury that is transported in rivers of the Mackenzie River basin, all the way down to the Beaufort Sea.

Project Description: The goal of this project is to identify and quantify (measure) the different possible sources of toxic mercury that is transported in rivers of the Mackenzie River basin, all the way down to the Beaufort Sea. In particular, the research team want to establish how much mercury comes from "modern" sources (like distant air pollution, runoff from rain/snow, wash-out from surface soils, etc.) and how much comes from "ancient" sources (old sediments, rocks, melting permafrost). This information is needed to figure out how fast the Arctic can "recover" from mercury pollution when emissions from the south are cut off. The project is a collaboration between four Universities in Sweden and in Canada. Sweden has a very similar landscape to much of Canada (boreal forest, very many rivers and lakes), and the country has struggled with problems of high mercury in fish for many decades, which is why they are interested and supporting this project. To find out about the different mercury sources to the Mackenzie River, the research team propose to collect some water from different parts of its drainage basin across the NWT. The team will then measure and compare the amounts of different types (isotopes) of both mercury and carbon in the water samples. The possibility of separating mercury isotopes is fairly new. It can be used, for example, to identify how much mercury from human pollution is found in the sediments of lakes, because different sources of mercury have different isotopes (their "fingerprints"). In this project, the team want to use the same approach with river water. The research team also know that the mercury in lakes and river water is usually bound with organic matter, such as decomposing plant remains or soil particles. Some of this organic matter is "modern" (a few years to 10s of years old) and some is "ancient" (1000s of years old) if it comes from old sediments or rocks. By separating carbon isotopes, the team can tell how much "young" and "ancient" carbon is in the water, and also how much mercury is from modern sources (like human pollution), and how much is from old sediments, rocks or ancient permafrost. The research team therefore propose to have a small team (3 people) travel by road across parts of the NWT and collect samples of river water by boat. The water samples will then be shipped for analysis in laboratories in Canada (Yellowknife, Ottawa, Peterborough) and in Sweden. The team selected 17 possible locations in the North Slave, South Slave, Dehcho and Inuvialuit/Gwich'in regions that can be accessed by road. There are also 3 places (1 in the South Slave region, 2 in the Sahtu region) that cannot be accessed by road. The team will ask staff from Environment Canada to collect samples for the project at these 3 places: they are part of their regular water quality monitoring network, which they visit several times per year. The research team would like to sample as many of the other 17 road-accessible sites as possible in June-July 2018, during the period when the river flow is high. It is important to get the water samples from the middle of rivers, not near the banks. The amount of water that the team need to collect at each place is about 8 liters (2 gallons). Because the amount of mercury in river water is very low (typically, less than 10 parts of mercury for 1 million parts of water), the team need 8 liters of water to get enough mercury for the analysis. The river water will be simply scooped from below the surface with a bottle suspended on a cable. The water will then be filtered and split between different bottles (one for each laboratory), and these will be shipped by regular air courier from Yellowknife or from Inuvik. During the field visit in the summer of 2018, the research team can visit communities and give presentations on the goals/methods of the project. The team are presently communicating with communities to see what can be done, where, and when. The team also plan to make a separate visit to some towns and/or communities in 2019 or in 2020 to report on the results of the project (when all the laboratory work is finished). This would probably be in autumn. The team will try to coordinate the trip with outreach activities such as community workshops that are sometimes organized by the NWT Cumulative Impact Monitoring Program (CIMP). The NWT Environmental Research Bulletin on the internet is also a good place to report our findings. In 2019 and/or 2020, the team plan to present the findings of the project at the annual Arctic Net conference, where there is always a good representation from northern communities. Finally, we can produce a fact sheet, poster or similar education material that can be distributed widely and used for both outreach and teaching. The fieldwork for this study will be conducted from June 7, 2018 to July 7, 2018.