Distribution of arsenic in surficial deposits in the Cold Lake area of Alberta, Canada

• Author / Creator

  Javed, Muhammad B

• Arsenic (As) concentration above the Health Canada and WHO drinking water guidelines of 10 µg L-1 in the Cold Lake area, Alberta is an issue of concern for environmental and human health. The source of groundwater As is ambiguous. This study was initiated to characterize the surficial deposits (sediments) drilled up to ~300 m depth from five different locations in the area to determine distribution and fractionation of As in sediments so that the potential source(s) of groundwater As could be inferred.
  Total As concentration in sediments (n = 135) ranged from 0.8 to ~35 µg g-1, but no significant correlation was found between As and sediments depth, lithology or geological formation. Maximum average As (~32 µg g-1; n = 2) was found in sediments derived from shale. In addition, 20-25 µg g-1 As was also found in glacial till of Bonnyville, Grand Centre and Empress formations at some depths, might be due to mixing of underlying shale during glaciation.
  To study the association of As with different inorganic and organic phases in sediments, a modified sequential extraction method was developed and employed on selected sediments (n = 22). Around 6-46 % of the total As was exchangeable and specifically adsorbed in all the sediments. Sediments having 7-35 µg g-1 As also contained significant sulfide bound As (11-34 % of total As). XRD and SEM-EDX analyses confirmed the presence of pyrite (FeS2), and µ-XRD analysis signaled the presence of arsenopyrite (FeAsS) in high As sediments (~20 µg g-1 As). XANES spectroscopy showed dominance of arsenite (AsIII; ~60-90 % of total As) in all the sediments.
  In addition, effect of heat on As release from sediments was also studied to simulate the condition in the sediments near the steam injection wells that are installed for bitumen extraction. Effect of thermal treatment (~200o C heat) on As release from sediments exhibited significant increase in the dissolved As concentrations (from 120 µg L-1 to ~1400 µg L-1) in the synthetic aquifer water. These findings may help understand the effect of in-situ oil extraction technique such as cyclic steam stimulation (CSS) on As and other metal mobilization in aquifers/groundwater.
  A detailed speciation method for AsIII, AsV and DMAA was also optimized, so that if a fresh core would acquire from the area As speciation could reliably be studied to infer the mobility and toxicity of As.

• Subjects / Keywords

  • Cold Lake area
  • Arsenic
  • Alberta
  • Sediments

• Graduation date

  Spring 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R36W6Z

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.