Effects of weathering on the dispersion of crude oil through oil-mineral aggregation

- Different types of artificially weathered oils were used to study OMA formation.
- For all oil types, the amount of oil dispersed as OMA decreases with weathering.
- Reduction in OMA formation is controlled by physical rather than chemical effects.
- After 32 h of weathering, 35% of light and 1% of heavy crude were dispersed.

Crude oil that is inadvertently spilled in the marine environment can interact with suspended sediment to form oil-mineral aggregates (OMA). Researchers have identified OMA formation as a natural method of oil dispersion, and have sought ways to enhance this process for oil spill remediation. Currently there is a lack of understanding of how the weathering of oil will affect the formation of OMA due to a lack of published data on this relationship. Based on literature, we identified two conflicting hypotheses: OMA formation 1) increases with weathering as a result of increased asphaltene and polar compound content; or 2) decreases with weathering as a result of increased viscosity. While it is indeed true that the viscosity and the relative amount of polar compounds will increase with weathering, their net effects on OMA formation is unclear. Controlled laboratory experiments were carried out to systematically test these two conflicting hypotheses. Experimental results using light, intermediate, and heavy crude oils, each at five weathering stages, show a decrease in OMA formation as oil weathers.

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