Estimating Geochemical Background Concentrations of Arsenic in Soil in the Yellowknife Area

Presenter:

 

Heather Jamieson – jamieson@queensu.ca

 
 

Authors:

 
M.J. Palmer – Aurora Research Institute, Aurora College, Yellowknife, NT; Carleton University, Ottawa, ON, Canada
H.E. Jamieson – Queen’s University, Kingston, ON, Canada
A. Radková – Queen’s University, Kingston, ON, Canada
K. Maitland – Queen’s University, Kingston, ON, Canada
J. Oliver – Queen’s University, Kingston, ON, Canada
H. Falck – Northwest Territories Geological Survey, Yellowknife, NT, Canada
M. Richardson – Carleton University, Ottawa, ON, Canada
 

Summary:

The estimation of geochemical background can be complex in areas impacted by point sources of atmospheric emissions due to unknowns about pollutant dispersion, persistence of pollutants on the landscape and natural concentrations of elements associated with parent material. We used a combination of statistical, geospatial, and mineralogical methods to estimate the range and upper thresholds of geochemical background for arsenic (As) in soils in the Yellowknife area, which have been impacted by more than 60 years of As-rich atmospheric mining emissions (1938-1999). High concentrations of As (up to 4700 mg kg-1) were measured in publicly accessible areas in the region. Strong relationships between As and distance from local emission sources persist in surface soils and soils at depth. Mineralogical assessment of surface soils highlighted that the majority of As in soils within 15 km of Yellowknife is hosted as arsenic trioxide from roaster emissions in the region. Analysis of an existing till geochemistry database (N = 1490) for the Slave Geological Province suggested that geochemical background for the region is 0.25 – 15 mg kg-1, with slightly higher upper thresholds in volcanic lithology units (30 mg kg-1) due to sulfide mineralization in greenstone belts. These results demonstrate the strength of using multiple methods to estimate geochemical background in areas of legacy mining pollution.

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