Heavy Metals in Bottom Sediments of the Mainstem Athabasca River System in the AOSERP Study Area

Dredged sediments and sediment cores were collected from sites along the Athabasca River system from between Fort McMurray and the confluence of Riviere des Rochers with the Slave River. A selected sample suite representing all of the drainage units and textural variations was analysed by several total and partial element extraction techniques. None of the metal concentrations detected were unusual. The results indicate that total concentrations are low when compared to data for natural and for polluted sediments elsewhere. Concentration variations are functions of natural fluvial, geochemical processes and are strongly affected by sedimentological parameters including sediment texture, Fe/Mn mineral coatings, organic and carbonate contents. There was a general progression to higher concentrations of heavy metals downstream from the Athabasca River to its delta to Lake Athabasca. The highest heavy metal concentrations were in the fine textured sediments from Lake Athabasca. Vanadium and nickel were strongly correlated with each other and with organic carbon content. V and Ni appear to be present in the bottom sediment in an organic form, unextractable by benzene/methanol, sodium hydroxide, or dilute hydrochloric acid.