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Abstract Title: Assessing the effectiveness and long-term effects of reactive capping amendments within simulated contaminated wetland columns
Presenter Name: David Lewis
Company/Institution: Saint Mary's Universirt
Session: Mercury in Contaminated Sites
Co-Authors: David Lewis

Abstract Information :

From the 1860s to the 1940s, Nova Scotia, Canada, had over 300 gold mines within 64 different districts. Mercury amalgamation was used to extract the gold from the host rocks with elevated geogenic arsenic. Historically, the mine waste (tailings) containing high concentrations of mercury and arsenic were disposed directly into shallow waterways and wetlands. Elevated mercury and arsenic in the sediment and surface water exceeding national guidelines still persist within at those sites. Sediments from these sites are toxic to invertebrates, and contaminants are bioaccumulating in organisms living in these wetlands. Environmental risks associated with these legacy tailings will therefore need to be managed. Preliminary laboratory results have demonstrated that adding a proprietary zero-valent iron (ZVI)/zeolite reactive amendment to the sediment together with a thin protective capping decreases the available mercury and arsenic in the sediment and in the overlying water to aquatic invertebrates. There is potential to scale up this application for remediation of contaminated wetlands without large-scale dredging or infilling, but it is important to investigate whether this decreases mobility of Hg and As. The purpose of this project is to assess the long-term effectiveness of the reactive amendment/protective capping technique in decreasing mobile and bioavailable species of Hg and As. This will be accomplished through a column leaching experiment spanning over one year. Free-draining columns will simulate small portions of the wetlands with contaminated sediment, reactive amendment, and a thin protective capping. Changes in the water conditions (pH, dissolved oxygen and redox potential) as well as dissolved concentrations of As(v), As(III), Fe(III), Hg (II), and sulphate in the porewater will be assessed at different depths of the core using sensors. The poster will present background information regarding the project, design concepts for the columns, and preliminary results from the sensors.

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