Atmospheric Deposition of Mercury and Methylmercury to Landscapes and Waterbodies of the Athabasca Oil Sands Region

• Published in: Environmental science & technology 2014-07, Vol.48 (13), p.7374-7383
• Main Authors: Kirk, Jane L, Muir, Derek C. G, Gleason, Amber, Wang, Xiaowa, Lawson, Greg, Frank, Richard A, Lehnherr, Igor, Wrona, Fred
• Format: Article
• Language: English
• Subjects: Alberta; Animal, plant and microbial ecology; Applied ecology; Applied sciences; Atmosphere - chemistry; Biological and medical sciences; Earth sciences; Earth, ocean, space; Ecotoxicology, biological effects of pollution; Engineering and environment geology. Geothermics; Environmental science; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General aspects; Global environmental pollution; Heavy metals; Mercury; Mercury - analysis; Methylmercury Compounds - analysis; Oil and Gas Fields; Oil sands; Pollution; Pollution, environment geology; Seasons; Silicon Dioxide - chemistry; Snow; Water Pollutants, Chemical - analysis; Water Pollution - analysis
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es500986r

Atmospheric deposition of metals originating from a variety of sources, including bitumen upgrading facilities and blowing dusts from landscape disturbances, is of concern in the Athabasca oil sands region of northern Alberta, Canada. Mercury (Hg) is of particular interest as methylmercury (MeHg), a neurotoxin which bioaccumulates through foodwebs, can reach levels in fish and wildlife that may pose health risks to human consumers. We used spring-time sampling of the accumulated snowpack at sites located varying distances from the major developments to estimate winter 2012 Hg loadings to a ∼20 000 km2 area of the Athabasca oil sands region. Total Hg (THg; all forms of Hg in a sample) loads were predominantly particulate-bound (79 ± 12%) and increased with proximity to major developments, reaching up to 1000 ng m–2. MeHg loads increased in a similar fashion, reaching up to 19 ng m–2 and suggesting that oil sands developments are a direct source of MeHg to local landscapes and water bodies. Deposition maps, created by interpolation of measured Hg loads using geostatistical software, demonstrated that deposition resembled a bullseye pattern on the landscape, with areas of maximum THg and MeHg loadings located primarily between the Muskeg and Steepbank rivers. Snowpack concentrations of THg and MeHg were significantly correlated (r = 0.45–0.88, p < 0.01) with numerous parameters, including total suspended solids (TSS), metals known to be emitted in high quantities from the upgraders (vanadium, nickel, and zinc), and crustal elements (aluminum, iron, and lanthanum), which were also elevated in this region. Our results suggest that at snowmelt, a complex mixture of chemicals enters aquatic ecosystems that could impact biological communities of the oil sands region.