Laboratory study of main weathering processes of oil spilled in the marine environment

The methodology and results of studying the main weathering processes of oil spilled in the marine environment are presented in this paper. Evaporation, dissolution, emulsification and natural dispersion were considered. The influence of oil weathering processes on the selection of oil spill response method (mechanical, physicochemical, or thermal) was estimated. The tests were carried out using various oil samples recovered in the Russian Federation taking into account the hydrometeorological conditions of the seas located in temperate latitudes. The low significance of natural dispersion for the fate of oil spill was established (especially under conditions of calm sea state and in the case of bituminous superviscous oil). Evaporation and emulsification were confirmed to be the most important oil weathering processes from the point of view of selecting an oil spill response method. The physicochemical properties of oil can change dramatically during these processes. It was shown that the evaporation losses for light low-viscosity oil were much greater than those for bituminous superviscous oil. This was reflected in the density and dynamic viscosity of the resulting residues. It was noted that evaporation of a significant proportion of light oil fractions can negatively affect the effectiveness of dispersant application and in situ burning. A high tendency to be emulsified (regardless of conditions) was revealed for bituminous superviscous oil. This led to obtaining emulsions with very high water content and dynamic viscosity. The necessity to take into account the physicochemical properties of residues formed as a result of oil evaporation and emulsification on the water surface when selecting oil spill response method or oil spill modeling method was noted. The compounds (alkanes, cycloalkanes, aromatic hydrocarbons and organic sulfides) capable of changing water toxicological characteristics were registered in the water samples taken after tests of studying the oil dissolution process.