Characterization of PAHs contamination from unconventional bitumen derived synthetic crude oil in soil microcosms: composition, ecotoxicity and loss rate. (1st March 2022) - Li, Ziang
Highlights: A sharp difference of PAH profile exists between SCO-soil and Texas-soil. SCO-soil were dominated by heavy alkylated PAHs with over-the-limit concentration. Contrasted PAH-loss rates observed between SCO-soil and Texas-soil. Previous benchmark PAHs such as EPA priorities could be misleading for SCO analysis. Abstract: The increasing exploitation of the unconventional bitumen-derived oils from Alberta (Canada) have raised new environmental concerns because they are inherently different than conventional oils. Previous studies mainly focused on diluted bitumen, but the Synthetic Crude Oil (SCO) which takes 35% of market share (of bitumen oils) has not been well studied. The main purpose of this study was to characterize PAHs in the SCO, since they are usually high-risk contaminants that often being prioritized in environmental monitoring practices. The obtained PAHs profile of SCO was also compared to that from a common benchmark oil, the Texas intermediate crude. PAH composition and eco-toxicity (based on Escherichia coli, Eisenia andrei and Lactuca sativa ) were studied by spiking the oil in soil microcosms. Results showed a sharp difference in relative abundance of PAH between SCO spiked soil (SCO-soil) and Texas-soil. SCO-soil were characterized by a significantly higher fraction of heavy PAHs (with 3- to 6-rings), 85% versus 36% of relative abundance in Texas-soil. The two soils were also characterized by contrasted PAH-loss rates (82% for SCO-soil and 93% for Texas-soil) likely resulting from their contrasted composition. As for the eco-toxicity, SCO had generally lower toxicity of than Texas. This could attribute to the lower total PAHs concentration and the lower bioavailability of heavy PAHs more abundant in SCO than Texas. This study also suggests that evaluations of oil contamination in soil using selected regulated PAHs would be incomplete and biased for SCO that contains a large fraction of unregulated alkylated PAHs.