Stable isotope method for tracing oil sands bitumen sources, differentiating δ13C in four carbon fractions in water and acid-extractable organics

This study was conducted at an oil-sands operation in the North Athabasca Oil Sands Region, Alberta, Canada to identify suitable isotopic tracers for differentiating between processed (anthropogenic) and non-processed bitumen residues in water. A combination of isotopes of water, solutes, and acid-extractable organics (AEO) were measured in tailings ponds containing oil-sands process water (OSPW), groundwater from the basal McMurray Formation, and a variety of on-lease groundwater monitoring wells and mitigation structures, the latter designed to intercept potentially contaminated runoff. This study provides supporting evidence that tailings ponds are well-contained and are not hydraulically connected with monitoring wells in local Quaternary aquifers or underlying formations at the investigated site. Testing included individual isotopic tracers and dual isotope pairs, as well as comprehensive suites of both isotopes and naphthenic-acid (NA) species. An isotopic approach using δ¹³C in four distinct carbon fractions emerges from our assessment as a promising method for operational fingerprinting of processed and non-processed bitumen residues in water for tracking potential OSPW seepage at oil sands operations.