Peat Bogs Document Decades of Declining Atmospheric Contamination by Trace Metals in the Athabasca Bituminous Sands Region

Peat cores were collected from five bogs in the vicinity of open pit mines and upgraders of the Athabasca Bituminous Sands, the largest reservoir of bitumen in the world. Frozen cores were sectioned into 1 cm slices, and trace metals determined in the ultraclean SWAMP lab using ICP-QMS. The uppermos...

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Bibliographic Details
Published in:Environmental science & technology 2017-06, Vol.51 (11), p.6237-6249
Main Authors: Shotyk, William, Appleby, Peter G, Bicalho, Beatriz, Davies, Lauren J, Froese, Duane, Grant-Weaver, Iain, Magnan, Gabriel, Mullan-Boudreau, Gillian, Noernberg, Tommy, Pelletier, Rick, Shannon, Bob, van Bellen, Simon, Zaccone, Claudio
Format: Article
Language:English
Subjects:
Age
Air Pollutants
Alberta
Antimony
Asphalt
Atmosphere
Bogs
Cadmium
Contamination
Continental crust
Cores
Enrichment
Environmental Monitoring
Lead
Metal concentrations
Metals
Molybdenum
Nickel
Peat
Peat bogs
Plant fossils
Sand
Silver
Soil
Spectrometry
Thorium
Trace elements
Trace metals
Wetlands
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Summary:Peat cores were collected from five bogs in the vicinity of open pit mines and upgraders of the Athabasca Bituminous Sands, the largest reservoir of bitumen in the world. Frozen cores were sectioned into 1 cm slices, and trace metals determined in the ultraclean SWAMP lab using ICP-QMS. The uppermost sections of the cores were age-dated with 210Pb using ultralow background gamma spectrometry, and selected plant macrofossils dated using 14C. At each site, trace metal concentrations as well as enrichment factors (calculated relative to the corresponding element/Th ratio of the Upper Continental Crust) reveal maximum values 10 to 40 cm below the surface which shows that the zenith of atmospheric contamination occurred in the past. The age-depth relationships show that atmospheric contamination by trace metals (Ag, Cd, Sb, Tl, but also V, Ni, and Mo which are enriched in bitumen) has been declining in northern Alberta for decades. In fact, the greatest contemporary enrichments of Ag, Cd, Sb, and Tl (in the top layers of the peat cores) are found at the control site (Utikuma) which is 264 km SW, suggesting that long-range atmospheric transport from other sources must be duly considered in any source assessment.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.6b04909