Sunlight has dramatic impacts on the fate of petroleum in environmental systems. The numerous chromophores in the oil result in both direct and indirect photolysis. Photochemistry results in oxygenation across multiple molecule types, including high and low molecular weight species, alkanes, aromatics, and heteroaromatics. Oxygenation changes the fate and transport of petroleum in environmental systems, potentially leading to greater bioavailability for biodegradation or toxicity. Oxygenation results in increased aqueous solubility of the photoproducts, but partitioning between the oil and aqueous phase depends on the size, functional groups, and extent of oxygenation of the molecules. Studies on oil irradiated with simulated sunlight have shown the production of acid, ketone, and aldehyde photoproducts, and we have assessed both time and temperature dependence of photoproduct formation. While the toxicity of individual compounds has not been assessed, we have observed that photoproducts dissolving in the aqueous phase exhibit genotoxic impacts. Photoproducts remaining in the oil phase have emulsifying capacity, and acidic functional groups play a major role in emulsification.

Sunlight and oil: Photoproducts, toxicity, and emulsification

ACS Spring 2022

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