Polycyclic Aromatic Hydrocarbons Increase in Athabasca River Delta Sediment: Temporal Trends and Environmental Correlates

The Athabasca River in Alberta, Canada, flows north through an area undergoing extensive bitumen resource extraction and processing before discharging its water and sediments into the Athabasca Delta and Lake Athabasca. Polycyclic aromatic hydrocarbons (PAHs) have been identified as an environmental concern in the region. We analyzed environmental data collected by the Regional Aquatics Monitoring Program and government agencies to determine whether temporal trends exist in the concentration of sediment PAHs in the Athabasca River Delta. We then determined what environmental factors related to the trends in sediment PAH concentrations. Total PAH concentrations in the sediment of the Athabasca River Delta increased between 1999 and 2009 at a rate of 0.05 mg/kg/yr +/- 0.02 s.e. Annual bitumen production and mined sand volume, extent of landscape disturbance, and particulate emissions were correlated with sediment PAR concentrations as were total organic carbon in sediment and discharge of the Clearwater River, a major tributary of the Athabasca River. Within four tributaries of the Athabasca River, only the Clearwater River showed a significant correlation between discharge and sediment PAH concentration at their river mouths. Carefully designed studies are required to further investigate which factors best explain variability in sediment PAR concentrations.