English to French Tech/Engineering Petroleum Eng/Sci Oil extraction process

When crude oil is released into the environment, physical and biological processes—collectively referred to as weathering—immediately begin to alter its composition. Evaporation, dissolution into water, sorption to soils, photo-oxidation, and biological degradation each affect the distribution of fugitive crude oil hydrocarbons in the environment , , , . The most rapid weathering changes are volatilization and solubilization of the light hydrocarbons in the C6 to C16 range . This carbon range can account for approximately one third of crude oil . The light hydrocarbon fractions of crude oil accidentally released at tropical latitudes can be completely degraded within days or weeks of the initial spill. Once the volatile hydrocarbons are lost, aerobic microbial degradation of the remaining hydrocarbon mass becomes the major oil weathering pathway. The relative rates of biodegradation follow a logical process where the bacteria will generally degrade the most energy-rich, kinetically labile compounds first (e.g., normal alkanes) followed by least energy rich and recalcitrant compounds (e.g., polycyclic aliphatic biomarker compounds such as the tricyclic terpanes). In general, microbial degradation / weathering rates decrease as follows :