Oil Weathering

Oil weathering is the set of physical and chemical processes that change spilled oil’s composition and behavior over time. Evaporation removes the light, volatile fractions within hours to days and is the largest mass-loss term for light crudes. Emulsification incorporates water to form stable water-in-oil emulsions (mousse) that can hold 70% or more water, raising viscosity and recoverable volume. Natural dispersion, dissolution, photo-oxidation, sedimentation, and biodegradation act in parallel. Weathering controls which response options stay effective: dispersants and in-situ burning lose effectiveness once emulsions form and viscosity climbs, so response timing is driven by the weathering state.