| Evaporation is one of the most significant weathering processes that can act on spilled oils, either at the surface or in the subsurface. Most of the volatile fraction, considered to be C10 and lower molecular weight compounds, is rapidly lost. Proceeding evaporation usually develops a vertical compositional profile. Laboratory studies were used to establish the chemical composition through vertical columns of Hunton, Glenpool, and Chinese Blend oils, and hydrocarbon ratios were quantified by gas chromatography after different times of evaporation from the surface. The compositional change experiments were designed to simulate two categories of environmental settings: first, evaporation of spilled oil in oil pools, and second, evaporation of oil located between different sizes of sand grains in the subsurface.; Documenting the compositional changes in spilled oil is essential for a full understanding of the fate and behavior of oil in the environment. FEMLAB computer software has been used to simulate the experimental compositional profiles of the different API gravity crude oils (i.e., Hunton, Glenpool, and Chinese Blend oils) produced by evaporation. Computer modeling helps by adding an additional approach to understanding the role of diffusion and convection processes in developing the compositional profiles of crude oil measured in laboratory experiments.; The computer modeling predicts that the diffusion process is dominant in changing the compositional profiles of crude oils. On the other hand, convection can occur along with diffusion through both light and heavy crude oils. Convection can occur in light crude oil as a consequence of diffusion, and it is then called diffusion-induced convection. However, convection usually occurs in heavier crude oils, where it is caused by gravitational forces due to changing densities caused by evaporation, and it is then called buoyancy-induced convection. |
