Assessment of mercury enrichment in lake sediment records from Alberta Oil Sands development via fluvial and atmospheric pathways

Exploitation of bitumen-rich deposits in the Alberta Oil Sands Region (AOSR) by large-scale mining and processing activities has generated widespread concern about the potential for dispersal of harmful contaminants to aquatic ecosystems via fluvial and atmospheric pathways. The release of mercury has received attention because it is a potent neurotoxin for wildlife and humans. However, knowledge of baseline mercury concentration prior to disturbance is required to evaluate the extent to which oil sands development has contributed mercury to aquatic ecosystems. Here, we use stratigraphic analysis of total mercury concentration ([THg]) in radiometrically dated sediment cores from nine floodplain lakes in the AOSR and downstream Peace-Athabasca Delta (PAD) and two upland lakes in the PAD region to establish pre-1900 baseline [THg] and evaluate if [THg] has become enriched via fluvial and atmospheric pathways since oil sands mining and processing began in 1967. Concentrations of THg in sediment cores from the study lakes range from 0.022–0.096 mg/kg (dry wt.) and are below the Canadian interim sediment quality guidelines for freshwater (0.17 mg/kg). Results demonstrate no enrichment of [THg] above pre-1900 baseline via fluvial pathways at floodplain lakes in the AOSR or PAD. Enrichment of [THg] was detected via atmospheric pathways at upland lakes in the PAD region, but this occurred prior to oil sands development and aligns with long-range transport of emissions from coal combustion and other anthropogenic sources across the northern hemisphere recognized in many other lake sediment records. The inventory of anthropogenic [THg] in the upland lakes in the AOSR is less than at the Experimental Lakes Area of northwestern Ontario (Canada), widely regarded as a “pristine” area. The absence of enrichment of [THg] in lake sediment via fluvial pathways is a critical finding for stakeholders, and we recommend that monitoring at the floodplain lakes be used to inform stewardship as oil sands operators prepare to discharge treated oil sands process waters directly into the Athabasca River upstream of the PAD.

[1]  R. Hall,et al.  A new lake classification scheme for the Peace-Athabasca Delta (Canada) characterizes hydrological processes that cause lake-level variation , 2021, Journal of Hydrology: Regional Studies.

[2]  W. Shotyk,et al.  Trace elements in the Athabasca Bituminous Sands: A geochemical explanation for the paucity of environmental contamination by chalcophile elements , 2021 .

[3]  R. Hazewinkel,et al.  A critical review of the ecological status of lakes and rivers from Canada's oil sands region , 2021, Integrated environmental assessment and management.

[4]  M. Dubé,et al.  An integrated knowledge synthesis of regional ambient monitoring in Canada's oil sands , 2021, Integrated environmental assessment and management.

[5]  R. Hall,et al.  Evaluating spatiotemporal patterns of arsenic, antimony, and lead deposition from legacy gold mine emissions using lake sediment records , 2021, Applied Geochemistry.

[6]  R. Hall,et al.  Evaluating Lower Athabasca River Sediment Metal Concentrations from Alberta Oil Sands Monitoring Programs Using Predevelopment Baselines. , 2021, Environmental Science and Technology.

[7]  R. Hall,et al.  Building upon open-barrel corer and sectioning systems to foster the continuing legacy of John Glew , 2020, Journal of Paleolimnology.

[8]  R. Hall,et al.  Assessment of vanadium and nickel enrichment in Lower Athabasca River floodplain lake sediment within the Athabasca Oil Sands Region (Canada). , 2020, Environmental pollution.

[9]  R. Hall,et al.  Multi-year isoscapes of lake water balances across a dynamic northern freshwater delta , 2020, Environmental Research Letters.

[10]  R. Hall,et al.  Evaluating temporal patterns of metals concentrations in floodplain lakes of the Athabasca Delta (Canada) relative to pre-industrial baselines. , 2020, The Science of the total environment.

[11]  J. Blais,et al.  Determining the effects of past gold mining using a sediment palaeotoxicity model. , 2020, The Science of the total environment.

[12]  R. Hall,et al.  Use of pre-industrial baselines to monitor anthropogenic enrichment of metals concentrations in recently deposited sediment of floodplain lakes in the Peace-Athabasca Delta (Alberta, Canada) , 2020, Environmental Monitoring and Assessment.

[13]  List of World Heritage in Danger , 2019, Dictionary of Geotourism.

[14]  P. Chambers,et al.  Accumulating Mercury and Methylmercury Burdens in Watersheds Impacted by Oil Sands Pollution. , 2019, Environmental science & technology.

[15]  R. Hall,et al.  Bi-directional hydrological changes in perched basins of the Athabasca Delta (Canada) in recent decades caused by natural processes , 2019, Environmental Research Communications.

[16]  C. Hebert.  The river runs through it: The Athabasca River delivers mercury to aquatic birds breeding far downstream , 2018, bioRxiv.

[17]  M. Mcmaster,et al.  Spatial trends in a biomagnifying contaminant: Application of amino acid compound–specific stable nitrogen isotope analysis to the interpretation of bird mercury levels , 2018, Environmental toxicology and chemistry.

[18]  J. Wiklund,et al.  Spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region (Alberta, Canada) , 2017 .

[19]  J. Wiklund,et al.  Anthropogenic mercury deposition in Flin Flon Manitoba and the Experimental Lakes Area Ontario (Canada): A multi-lake sediment core reconstruction. , 2017, The Science of the total environment.

[20]  G. Birch.  Determination of sediment metal background concentrations and enrichment in marine environments - A critical review. , 2017, The Science of the total environment.

[21]  R. Macdonald,et al.  Spatiotemporal patterns of mercury accumulation in lake sediments of western North America. , 2016, The Science of the total environment.

[22]  R. Hall,et al.  Paleolimnological assessment of riverine and atmospheric pathways and sources of metal deposition at a floodplain lake (Slave River Delta, Northwest Territories, Canada). , 2016, The Science of the total environment.

[23]  D. Dixon,et al.  Use of pre-industrial floodplain lake sediments to establish baseline river metal concentrations downstream of Alberta oil sands: a new approach for detecting pollution of rivers , 2014 .

[24]  D. Muir,et al.  Atmospheric deposition of mercury and methylmercury to landscapes and waterbodies of the Athabasca oil sands region. , 2014, Environmental science & technology.

[25]  D. Engstrom,et al.  Atmospheric Hg emissions from preindustrial gold and silver extraction in the Americas: a reevaluation from lake-sediment archives. , 2014, Environmental science & technology.

[26]  Jeffrey P. A. Shatford,et al.  Mercury trends in colonial waterbird eggs downstream of the oil sands region of Alberta, Canada. , 2013, Environmental science & technology.

[27]  Nicola Pirrone,et al.  Mercury as a Global Pollutant: Sources, Pathways, and Effects , 2013, Environmental science & technology.

[28]  J. Smol,et al.  Legacy of a half century of Athabasca oil sands development recorded by lake ecosystems , 2013, Proceedings of the National Academy of Sciences.

[29]  D. Dixon,et al.  Has Alberta Oil Sands Development Altered Delivery of Polycyclic Aromatic Compounds to the Peace-Athabasca Delta? , 2012, PloS one.

[30]  D. Dixon,et al.  Has Alberta oil sands development increased far-field delivery of airborne contaminants to the Peace-Athabasca Delta? , 2012, The Science of the total environment.

[31]  A. Talbot,et al.  Investigations of mercury concentrations in walleye and other fish in the Athabasca River ecosystem with increasing oil sands developments. , 2012, Journal of environmental monitoring : JEM.

[32]  J. Sanchez-Cabeza,et al.  210Pb sediment radiochronology: An integrated formulation and classification of dating models , 2012 .

[33]  D. Schindler,et al.  Oil sands mining and reclamation cause massive loss of peatland and stored carbon , 2012, Proceedings of the National Academy of Sciences.

[34]  I. Renberg,et al.  Evaluation of conservative lithogenic elements (Ti, Zr, Al, and Rb) to study anthropogenic element enrichments in lake sediments , 2011 .

[35]  David Schindler,et al.  Tar sands need solid science , 2010, Nature.

[36]  Charlene C. Nielsen,et al.  Oil sands development contributes elements toxic at low concentrations to the Athabasca River and its tributaries , 2010, Proceedings of the National Academy of Sciences.

[37]  J. Smol,et al.  Spatial trends and historical deposition of mercury in eastern and northern Canada inferred from lake sediment cores. , 2009, Environmental science & technology.

[38]  R. Couture,et al.  Chronology of atmospheric deposition of arsenic inferred from reconstructed sedimentary records. , 2008, Environmental science & technology.

[39]  Bronwyn E. Brock,et al.  A coupled isotope tracer method to characterize input water to lakes , 2008 .

[40]  Andrew Heyes,et al.  Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition , 2007, Proceedings of the National Academy of Sciences.

[41]  D. Engstrom,et al.  Modeling the past atmospheric deposition of mercury using natural archives. , 2007, Environmental science & technology.

[42]  J. Schauer,et al.  Methyl and total mercury in precipitation in the Great Lakes region , 2005 .

[43]  S. A. Abdrashitova,et al.  Mercury in the Aquatic Environment: A Review of Factors Affecting Methylation , 2001 .

[44]  J. Nriagu,et al.  Historical atmospheric mercury emissions and depositions in North America compared to mercury accumulations in sedimentary records , 1998 .

[45]  E. Callender,et al.  Environmental Policy Analysis, Peer Reviewed: Reservoir Sediment Cores Show U.S. Lead Declines , 1997 .

[46]  Ralph Mitchell,et al.  Sulfate stimulation of mercury methylation in freshwater sediments , 1992 .

[47]  D. Loring.  Normalization of heavy-metal data from estuarine and coastal sediments , 1991 .

[48]  J. Glew.  A new trigger mechanism for sediment samplers , 1989 .

[49]  J. Glew.  A portable extruding device for close interval sectioning of unconsolidated core samples , 1988 .

[50]  S. Krupa,et al.  Mercury Concentration and Isotopic Composition of Epiphytic Tree Lichens in the Athabasca Oil Sands Region , 2012 .

[51]  John P. Smol,et al.  A FOUNDATION FOR THE FUTURE: BUILDING AN ENVIRONMENTAL MONITORING SYSTEM FOR THE OIL SANDS , 2010 .

[52]  R. Hall,et al.  Hydroecological responses of the Athabasca Delta, Canada, to changes in river flow and climate during the 20th century , 2008 .

[53]  Peter G. Appleby,et al.  Chronostratigraphic Techniques in Recent Sediments , 2002 .

[54]  Canadian Sediment Quality Guidelines for the Protection of Aquatic Life ZINC , 1999 .