Aerobic fate and impact of canola oil in aquatic media

The fate of canola oil in water under aerobic conditions was studied in respirometry tests. First-order biodegradation rates were estimated for a refined oil (commercial canola oil, CCO), 0.0037 h⁻¹, and for two synthetic oils, one prepared with mono-acid triacylglycerols (TAO) 0.0048 h⁻¹, and the other with free fatty acids and glycerol (FAO) 0.0038 h⁻¹. Two abiotic factors limited substrate bioavailability: the autoxidation of the oleoyl chains and the insolubility of fully saturated triacylglycerols. In addition, the ecotoxic impact of the oils was assessed by Microtox^® toxicity. For the acylglycerol oils, luminescent bacteria inhibition was not detected in the water phase, whereas solid-phase EC₅₀ values below 1.8% sample volume were measured. Toxicity was observed in the aqueous phase (EC₅₀ < 16%) during the biodegradation of FAO. In this case, however, solid-phase toxicity was extremely high at the beginning of the test (0.02%) but the toxicity dissipated 480 h into the experiment.