The Athabasca oil sands region (AOSR) in northeastern Alberta, Canada, is one of the world's largest oil reservoirs. Its heavy oil will become increasingly important as conventional energy resources decline. Due to the rapid industrial development in the AOSR, there have been increasing concerns about the impact of the emissions from the oil sands operations on the surrounding terrestrial and aquatic ecosystems. Stable isotope techniques may help to assess such impact provided that industrial emissions are isotopically distinct from background components. In order to trace nitrogen (N), sulfur (S) and molybdenum (Mo) emissions released by the oil sands industry, chemical and isotopic compositions of various N, S and Mo compounds in emissions and several environmental receptors were determined.

Industrial N and SO4 emissions were found to be isotopically distinct. δ18 O and Δ17 O of atmospheric nitrate deposition and δ18 O values of atmospheric sulfate deposition showed trends towards lower values with increasing nitrate and sulfate deposition rates allowing for the quantification of industrial contributions to atmospheric nitrate and sulfate deposition in the AOSR (quantitative tracers ). Lichens responded to elevated N and S deposition in close proximity to the oil sands operations, whereas chemical and isotopic compositions of N and S in pine needles showed no significant industrial impact. δ 15 N values of industrial emissions provide a qualitative tracer of industrial N emissions in atmospheric ammonium deposition, lichen samples and soil water. δ34 S values in atmospheric sulfate deposition and total S in lichen samples were indicative of emissions of reduced sulfur compounds, likely from tailing ponds. Different sample preparation techniques were tested for the analyses of δ98/95 Mo. Results of Mo concentration and isotope ratio analyses on snow, air filter samples and fly ash samples from a coal-fired power plant suggest that industrial activities are associated with an increase in Mo concentrations and with Mo isotope fractionation, providing a potential new tracer for industrial activities in the AOSR.

In summary, quantitative and qualitative tracers revealed that impact of industrial emissions on the surrounding environment in the AOSR were limited to 30 km distance to one of the major emission stacks.