Nonconventional oil products (Access Western Blend [dilbit], Western Canadian Select [dilsynbit], and Synthetic Bitumen [synbit]) and a conventional crude (Heidrun) were naturally weathered on sea water under spring (April-May) and summer (July-August) conditions to improve our understanding of the effects of climatic parameters (air and water temperature, wind speed, and light intensity [solar radiation]) on their density and viscosity.   The physical properties data, from each experiment, was fitted to a previously developed hyperbolic function that captured different rates of changes in densities and viscosities of the oils due to preferential weathering of the diluent portion of the diluted bitumen products. A combination of multiple correlation and regression analysis of experimental data over two seasons revealed that there were significant (p<0.05) trends among the measured climatic parameters and the changes in the densities and viscosities of oils after a spill. Analysis of variance (repeated measures) showed that seasonal conditions had a significant (p<0.01) effect on the changes in the physical properties of all oils after release. These results on key factors which control the rates of natural attenuation for nonconventional oils spilled on water will aid decision making during oil spill preparedness and response operations.

Keywords: Dilbit; Dilsynbit; Synbit; Oil Weathering; Climatic Parameters;