NWT RESEARCH DATABASE

Regions: North Slave Region

Tags: contaminants, site remediation, water quality, sediment chemistry, arsenic, hydrology, metals, hydrocarbon

Objective(s): To develop tools to assess risks associated with legacy industrial developments in a northern setting by investigating contaminants from the Giant Mine near Yellowknife NT.

Project Description: The research team will develop tools to assess risks associated with legacy industrial developments in a northern setting. The team will investigate contaminants from the Giant Mine near Yellowknife NT, which operated between 1948 and 2004, producing a legacy of contaminants including arsenic, antimony, hydrocarbons, mercury, and others. This remediation strategy only applies to the Giant Mine property, so the research will develop new tools to inform the government of the NT and other regulators on how to manage the land and water in areas surrounding the Mine property, as they are within the limits of NT’s largest population center. Specifically, the research team will (1) characterize metals (focusing on arsenic, antimony, and mercury), and hydrocarbons released from the mining operations to lake waters and lake sediment cores to determine current and historical chemical exposures to natural systems; (2) use fossilized invertebrate and algal assemblages to assess ecosystem responses to pollutants, which will be analyzed in lake sediment cores; and (3) develop microbiological tools to assess microbially mediated mercury transformations which affect methyl mercury ‘hotspots’ near these legacy industrial sites. 1: Characterizing the legacy contaminants from Giant Mine and Con Mine in sediment cores by paleoecotoxicology: The research team will use high-resolution lake sediment cores selected from lakes spanning a 50 km radius of Giant Mine to track the history of environmental pollution resulting from mining activities, including arsenic., Polycyclic aromatic hydrocarbons (PAHs) and other metals like antimony, lead and mercury will also be characterized. In addition to characterizing emissions from Giant Mine in archived sediment profiles, the research team will also address how biological assemblages in these same archives have changed as a result of pollution from the mine, using diatom and chrysophyte indicators to assess metal and hydrocarbon pollutants. Subtheme 2: Analysis of mercury methylation hotspots near Giant Mine: Mercury (Hg) is a priority contaminant that, in its methylated form, is a toxic substance that persists in the environment and is biomagnified through aquatic food webs. Once in the environment, mercury toxicity and bioaccumulation depend on in-situ synthesis of monomethylmercury (MMHg). The objective is to investigate the environmental controls on MMHg cycling in lakes around Yellowknife and test whether mining operations contribute to the development of methylation hotspots. Lake sediments, soils, and waters in the area near Yellowknife are enriched in arsenic due to the lack of pollution controls during the early years of gold mining as well as the naturally high arsenic associated with gold mineralization. The recent research on samples from the Giant mine property has shown that natural and anthropogenic (roaster-generated) arsenic can be distinguished in soils and sediments using microanalytical mineralogical techniques. The results of this research will contribute to improved risk assessment and remediation design. Sediment-pore water profiles from the peepers and adjacent cores will indicate whether arsenic is being released from sediments and diffusing upward into the overlying lake water. This is thought to be one of the most important mechanisms for arsenic enrichment in groundwater, both in mine-impacted sediments and arsenic-contaminated aquifers in south Asia. However, if sulfate-reducing bacteria are present, arsenic sulfide such as realgar may immobilize the arsenic and reduce bioavailability. The results will be published in the primary literature, so that all stakeholders within and outside of Canada will have access to the findings. Government partners will be part of this investigation and the results will be considered in the development of guidelines and procedures for management of contaminants in a changing northern climate. The research team will ensure that the results are presented in public meetings (e.g. Water Strategy meetings (NT), local stakeholder meetings), in poster format, and in annual community reports as part of the communications plan of this project. The Principal Investigators on this proposal communicate their research regularly to the press via television, radio and printed news. The fieldwork for this study will be conducted from May 7, 2015 to December 1, 2015.