Assessment of seven Canadian rivers in relation to stages in oil sands industrial development, 1972–2010

We compiled a 38 year dataset (1972 to 2010) to evaluate changes in water chemistry over time in relation to oil sands mining activities. We examined patterns in three focal elements (dissolved selenium, dissolved arsenic, total vanadium) at 96 sites along seven tributaries of the Athabasca and Clearwater Rivers. Concentrations of the three focal elements did not differ between sites sampled upstream versus downstream of future development, between sites upstream versus downstream of the primary bitumen-bearing geologic formation, or at an upstream site over a 33 year period on the Muskeg River (1976–2009). Hence, longitudinal patterns observed in water chemistry following mine development cannot be attributed to natural background variation. In contrast, concentrations and loads of the three focal elements were greater post-development compared to reference values (p ≤ 0.01), and were typically greatest during the early exploration and land clearing stage of mine development (p < 0.01). Positive correlations between our three focal elements and 17 other variables either associated with bitumen or considered priority pollutants (r ≥ 0.13, p ≤ 0.04) suggest that the historical impacts of oil sands development on water quality extend beyond our three focal parameters. These results indicate that erosion and subsequent runoff associated with land clearing, construction, and early operational activities have affected water quality in the oil sands region.