The fate of trace metals in pore water collected from wetland sediments and organisms exposed to petroleum
coke were evaluated within in situ aquatic microcosms. Oil sands operators of Fort McMurray, Alberta,
Canada produced 60 million tonnes of petroleum coke by 2008, containing elevated concentrations of
sulphur and several trace metals commonly seen in oil sands materials. This material may be included in
the construction of reclaimed wetlands. Microcosms were filled with a surface layer of petroleum coke
over mine-waste sediments and embedded in a constructed wetland for three years to determine how
these materials would affect the metal concentrations in the sediment pore water, colonizing wetland plants
and benthic invertebrates. Petroleum coke treatments produced significantly elevated levels of Ni. We also
found unexpectedly higher concentrations of metals in “consolidated tailings” waste materials, potentially
due to the use of oil sands-produced gypsum, and higher background concentration of elements in the
sediment used in the controls. A trend of higher concentrations of V, Ni, La, and Y was present in the tissues
of the colonizing macrophytic alga Chara spp. Aeshnid dragonflies may also be accumulating V. These results
indicate that the trace metals present in some oil sands waste materials could be taken up by aquatic macroalgae
and some wetland invertebrates if these materials are included in reclaimed wetlands.