Sediment from Lakes
Polycyclic aromatic hydrocarbons (PAHs), 47 elements including numerous metals, and visible reflectance spectroscopy or VRS-chla have been determined in sediment core samples collected in 2012, 2013 and 2014 from 16 small (surface area 4-97 ha; maximum depth ~1-5 m deep), hydrologically simple lakes located 30 to 120 km from major oil sands development areas.
Canadian Council of Ministers of the Environment (CCME) guidelines are available for 13 of the 53 PAHs reported here. Sediment concentrations did not exceed Canadian Council of Ministers of the Environment (CCME) probable effects levels (PELs), which define the level above which biological adverse effects are expected to occur, for PAHs in any lake. Exceedances of the CCME interim sediment quality guidelines (ISQG) for the protection of aquatic life occurred for 4 PAHs (naphthalene, 2-methyl naphthalene phenanthrene, and benzo(a)pyrene) in 8 lakes.
CCME sediment quality guidelines are available for 7 of the 47 elements reported here. Exceedances of the CCME ISQG for metals were found for arsenic in 3 lakes, cadmium in 8 lakes, mercury in 3 lakes and zinc in 9 lakes. Exceedances of the CCME PELs for metals occurred in 2 lakes for arsenic and 1 lake for zinc. Further assessment of the data is ongoing to examine reasons for exceedances as well as spatial and temporal trends of the PACs and elements.
Analyses of lake primary productivity, using visible reflectance spectroscopy or VRS-chla as a proxy, show consistently greater productivity (i.e. VRS-chla concentrations) in the top sediment core slices relative to the bottom, regardless of lake morphological and limnological characteristics and landscape position. Potential drivers of these changes are being examined.
