A multidisciplinary investigation of recovery in Yellowknife area lakes from 50 years of arsenic pollution: What are the factors inhibiting recovery and the biological consequences?
Principal Investigator: Palmer, Mike (2)
Licence Number: 16162
Organization: Carleton University
Licenced Year(s): 2018 2017
Issued: Aug 17, 2017
Project Team: John Chetelat (Co-supervisor, Env. Climate Change Canada), William Lines (Community liasion, Yellowknives Dene First Nation), Maikel Rosabal (Lead on fish work, Univ. Quebec at Montreal), Marc Amyot (Lead on arsenic photochemistry experiments, Univ. de Montreal), YKDFN field assistant (Field assistant, YKDFN), MSc student UQ at Montreal (MSc student (M. Rosabal supervisor), Univ. Quebec at Montreal), Gila Somers (Government Liasion , GNWT-Water Resources), Heather Jamieson (Support on arsenic geochemisty work, Queen's University), Mike Palmer (Principal investigator, Carleton University), Michael Gilday (Field assistant), Murray Richardson (Co-supervisor, Carleton University)

Objective(s): To investigate watershed and within-lake abiotic processes affecting the recovery of mine-impacted lakes in the Yellowknife area.

Project Description: The overarching objectives of this research are two-fold:
1) to investigate watershed and within-lake abiotic processes affecting the recovery of mine-impacted lakes in the Yellowknife area, including storage and release of arsenic from soils, seasonal dynamics of arsenic export in runoff, and fluxes of arsenic to and from lake sediments; and
2)to investigate the toxicological consequences of more than half a century of elevated contaminant levels on food chains in mine impacted lakes that show little sign of recovery.

The key research questions for this project include:
a) What are the current processes that are loading and removing arsenic from Yellowknife area lakes and how does this influence lake recovery?
i) Continued loading: how much arsenic continues to be derived from watershed sources, i.e. catchment soils, inflow from upstream lakes, and fluxes between contaminated lake sediments and overlying surface waters?
ii) Export processes: how much arsenic is exported downstream from the lake via lake outflow or retained in the lake through sedimentation processes?
iii) How do these processes vary seasonally, and what are the most important seasons for transport?
b) How do lake water conditions affect the diffusion of legacy arsenic from sediments and its speciation in the water column?
i) How do oxygen at the sediment-water interface and temperature affect the diffusion of arsenic from contaminated lake sediments?
ii) How do sunlight and water chemistry affect the speciation of inorganic arsenic in the water column?
c) How is legacy arsenic accumulating in food chains of mine impacted lakes?
i) What is the speciation of arsenic accumulating in fish and their invertebrate prey?
ii) What tissues are the main stores of arsenic and metals in fish?
iii) Are fish showing signs of toxicity at the cellular level?

The research team propose to conduct a multi-disciplinary study that integrates a variety of methods to better understand the processes controlling the slow recovery of Yellowknife lakes from legacy arsenic pollution and the toxicological consequences to aquatic food chains. The activities outlined below, which involve both field measurements and laboratory experiments, will be conducted over a three-year period to generate sufficient data to address the complex research questions and achieve the objectives.

Activity 1: Quantifying arsenic loading and removal processes in Yellowknife area lakes:
The research team propose to undertake detailed seasonal arsenic mass balance estimates for Lower Martin Lake in order to better understand the processes influencing lake recovery in the area. Mass balance models are an effective means of estimating and partitioning the relative fluxes of contaminants in watersheds and have been used successfully in past studies. The team have selected Lower Martin Lake as the primary location of study because it is the last lake in the Baker Creek system before the Giant Mine site and Yellowknife Bay and consequently the lake acts as a mediator for upstream contributions. Inputs and outputs from the watershed will be measured across seasons. This is rarely done, but is likely highly important in subarctic watersheds, where spring snowmelt may account for the bulk of metal(loid) transport. In addition, under-ice winter processes may lead to substantial enrichment of lake water arsenic via cryoconcentration and diffusion from contaminated lake sediments under anoxic conditions.

To carry out these mass balance estimates, the watershed will be divided into distinct terrestrial and aquatic ecosystem units so that potential source areas and fluxes between these areas can be quantified. Current atmospheric deposition of arsenic will be measured using rain collectors in the spring, summer, and fall and by measuring the chemical composition of the snow pack in late winter. Total arsenic concentrations will be measured in catchment soils from the various terrain units (open and closed canopy forests, bedrock outcrops, and wetlands). Arsenic mineralogy (i.e. solid state speciation) will be determined for a subset of samples (soil, sediments, stream particles) to identify the origin (natural vs anthropogenic) and mobility of arsenic in environmental reservoirs. Porewater arsenic concentrations in soils will be measured during summer and fall using piezometers and suction lysimeters in order to estimate the amount of water soluble arsenic available for transport. Lake waters will be sampled regularly to evaluate seasonal variations in lake water arsenic concentrations, including arsenic speciation. Regular sampling at lake inflows and outflows will be undertaken, with detailed sampling during freshet and during storm events, as these periods likely account for the bulk of arsenic transport in the watershed. Finally, the flux of dissolved arsenic from lake sediments will be estimated seasonally in the field using in situ measurements of lake sediment porewaters.

Activity 2: Toxicological consequences to aquatic food chains.
Arsenic bioaccumulation and speciation will be investigated in food chains of the study lakes to evaluate potential toxicological impacts on resident biota. Fish-bearing lakes (Long Lake, Lower Martin Lake) will be sampled for fish and their invertebrate prey (zooplankton, benthic invertebrates) using standard methods (Broad Scale Fish Community Monitoring Protocol). In fish-less lakes (e.g. Handle Lake), only aquatic invertebrates will be collected. Fish tissues and aquatic invertebrates will be analyzed for arsenic levels and speciation, and compared to published arsenic thresholds from the literature for toxicity in invertebrates and fish. In addition, tissues will be examined at the cellular level using a novel approach termed sub-cellular partitioning of elements. Aquatic invertebrate and fish tissues will be analyzed to determine where within cells arsenic and metals are distributed and to what sub-cellular components those elements are bound.

The Yellowknives Dene First Nation (YKDFN) are active partners in the proposed project. YKDFN members will be involved in project planning, collection of field data, and reporting back to the community. The project team will meet regularly with YKDFN members and staff. Part of the project includes training of a local YKDFN member as a field technician, who will assist the project team through the YKDFN office. The project team will provide regular updates to YKDFN staff of the Department of Lands and Environment and will be available to meet with chief and council should that be necessary. YKDFN staff will be provided with copies of all annual reports and presentations. The project team has worked extensively in the past with YKDFN staff from the Department of Lands and Environment, including providing plain language information via reports and presentations.

Information generated from this project will be summarized in annual reports to the Cumulative Impacts Monitoring Program (CIMP) and these reports will be shared with community groups and regulatory boards. Follow up conversations with researchers will be initiated if there is interest. The Principal Investigator for this project will be based in Yellowknife, and is readily available to discuss project details throughout the year.

Results from the project will directly inform the regulatory permitting process for the remediation of Giant Mine and results will be made available to the Mackenzie Valley Land and Water Board, the Giant Mine Remediation Team, and the Giant Mine Oversight Board through CIMP annual reports and through presentations to these organizations as required. Project team members are also available to participate as experts in the permitting process of remediation activities at Giant Mine should their services be required.

The fieldwork for this study will be conducted from August 25, 2017 to December 31, 2017.