Field Vegetation Assessment and Contaminants, Oil Sands Region

Plant species richness, composition, and soil chemistry parameters were assessed in wetlands and uplands in the oil sands region of northern Alberta. The concentrations of metals and polycyclic aromatic hydrocarbons (PAHs) were measured in soil and plant samples collected from 2012-2014, and naphthenic acids (NAs) from soil collected in 2012. Vegetation surveys and a seedbank study showed that plant species richness and composition differed among study sites, with more species (many non-native) found at sampling sites located within close proximity to oil sands development and infrastructure compared to sites located further afield. PAH and metal concentrations in soil at sites near oil sands industrial development were generally higher than levels at sites located outside of the immediate surface mining area. This finding was not unexpected given that PAHs and metals are naturally occurring in Alberta bitumen. Analysis of the data revealed that the PAH compounds naphthalene and anthracene exceeded soil quality guidelines established by the Ontario Ministry of the Environment (MOE) in eight and six of 22 sites sampled, respectively (ON MOE 2011). Similarly, 14 of 28 metals measured exceeded guidelines established by provincial (ON MOE 2011), national (Canadian Council of Ministers of the Environment (CCME) 2015), or international (US Environmental Protection Agency 2016) regulatory agencies in at least one sampling location. Soil quality guidelines do not currently exist for NAs. Results revealed that metals and PAHs could be detected in the plant samples collected. Overall, there were no noticeable phytotoxic effects on the plant communities at any of the sites surveyed. It is our expert opinion that the observed concentrations of these contaminants are not currently posing a contamination risk to wild plant populations in the region; however, plant communities should be monitored over a longer period for shifts in species composition and abundance.