A METAL SORPTION SIEVE PROCESS IN THE ALBERTA OIL SANDS (Invited Presentation)

The large-scale, industrial oil sands (OS) operations in Northern Alberta require massive tailings facilities to contain the waste byproducts, including oil sands process water (OSPW), produced from bitumen surface mining processes. The Athabasca Oil Sands Region (AOSR) is located within a Boreal Plains Ecozone, comprised of one-third wetland environments. Despite the abundant wetland environments in the AOSR, to date, there has been no investigation of the processes that occur as OSPW encounters the organic-rich substrates. This study focuses on organometallic complexes, and how they affect the mobility of mining-related, metal loads where tailings ponds are adjacent to organic-rich, wetland environments. Using advanced Orbitrap mass spectrometry for surface and groundwaters, this study demonstrates substantial attenuation of higher molecular weight organic compounds in groundwaters, with the highest attenuation in the most organic-rich wetland substrates, consistent with the sorption characteristics of humic substances. Most rare earth elements and trace metal loads also follow this attenuation pattern, with increased attenuation in wetland environments, even in wetland sites with overall increased metal loads, and in proportion with organometallic complexing affinity of different metals. Metals sorbed to humic substances as organometallic complexes are further sequestered out of solution to the substrate, resembling a sorption sieve process.