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TitleArsenic mobility in weathered gold mine tailings under a low-organic soil cover
AuthorDeSisto, S L; Jamieson, H E; Parsons, M BORCID logo
SourceEnvironmental Earth Sciences vol. 76, no. 773, 2017, 16 pages,
Alt SeriesNatural Resources Canada, Contribution Series 20170113
PublisherSpringer Nature
Mediapaper; on-line; digital
File formatpdf
ProvinceNova Scotia
NTS11D; 11F; 11E
AreaMontague Gold Mine; Sherbrooke; Mitchell Brook
Lat/Long WENS -63.5000 -61.0000 45.5000 44.5000
SubjectsHealth and Safety; environmental geology; tailings disposal; tailings analyses; tailings; mine dumps; mine waste products; mines; gold; leaching; column leaching; arsenic; Human health
Illustrationslocation maps; tables; graphs; stratigraphic columns
ProgramEnvironmental Geoscience Management
Released2017 11 16
AbstractHistorical gold mining operations in Nova Scotia, Canada resulted in numerous deposits of publicly accessible, arsenic (As)-rich mine waste that have weathered in situ for 75 to 150 years, resulting in a wide range of As-bearing secondary minerals. The geochemical heterogeneity of this mine waste creates a challenge for identifying a single remediation approach that will limit As mobility. A 30-cm thick, low-organic content soil cover was evaluated in laboratory leaching experiments where, to simulate natural conditions, the equivalent of two years of synthetic rainwater was leached through each column and two dry seasons were incorporated into the leaching protocol. Each column was a stratigraphic representation of the four major tailings types found at the historical Montague and Goldenville gold mine districts: hardpan tailings, oxic tailings, wetland tailings, and high Ca tailings. Hardpan tailings released acidic, As-rich waters (max. 12 mg/L) under the cover but this acidity was buffered by surrounding oxic tailings. Leachate from the oxic tailings was circumneutral, with average As concentrations between 4.4 and 9.7 mg/L throughout the experiment. The presence of carbonates in the high Ca tailings resulted in near-neutral to weakly alkaline leachate pH values, and average As concentrations between 2.1 and 6.1 mg/L. Oxidation of sulfides in the wetland tailings led to acidic leachate over time and a decrease in As concentrations to values that were generally less than 1 mg/L. This study shows that the use of a low-organic content soil cover does not create reducing conditions that would destabilize oxidized, As-bearing secondary phases in these tailings. However, oxygen penetration through the cover during dry seasons would continue to release As to tailings pore waters via sulfide oxidation reactions.
Summary(Plain Language Summary, not published)
Mine tailings at historical gold districts in Nova Scotia contain high concentrations of arsenic (As), which may represent a risk to ecosystems and human health. This study focused on two sites, Montague and Goldenville, where tailings are located close to residences and are occasionally used for racing off-road vehicles. This paper describes the results of detailed laboratory column studies of the tailings carried out by the first author as part of her Ph.D. thesis at Queen's University (completed in May 2014). The study has examined the effects of a low-organic soil cover on the mobility of As from weathered mine tailings when leached with simulated rain water in the lab. These results can be used to help guide future remediation activities at historical and modern gold mines in Nova Scotia, and at similar metal mining sites worldwide.

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