For over a decade, the contribution of oil sands mining and processing
to the pollution of the Athabasca River has been controversial. We
show that the oil sands development is a greater source of contamination
than previously realized. In 2008, within 50 km of oil sands
upgrading facilities, the loading to the snowpack of airborne particulates
was 11,400 T over 4 months and included 391 kg of polycyclic
aromatic compounds (PAC), equivalent to 600 T of bitumen, while 168
kg of dissolved PAC was also deposited. Dissolved PAC concentrations
in tributaries to the Athabasca increased from 0.009g/L upstream of
oil sands development to 0.023 g/L in winter and to 0.202 g/L in
summer downstream. In the Athabasca, dissolved PAC concentrations
were mostly